diesel engine warm-up question

topic posted Wed, August 16, 2006 - 12:12 PM by  andy
not a bio-specific question, but im curious about how important it is to warm up a diesel engine before driving, and the best ways to do this. a little searching yeilds very little diesel specific advice, so i though i would try here.

im driving an older diesel, an '81 240D mercedes. it clearly is sluggish while it is warming, but my question is whether it is important to warm it by sitting at idle, or if slow gentle driving is as effective. any info about how all this works, any potential to damage the engine, etc, would be appreciated.

also curious of any other input from on this from old benz drivers, like how much you use a block heater, turn up the idle, warm by driving, etc.

posted by:
  • Unsu...

    Re: diesel engine warm-up question

    Wed, August 16, 2006 - 3:56 PM
    A gentle idle warm up is the best. The amount of time is more dependent upon your weather conditions than anything. Living in CA, I usually warm up for about 2-3 minutes during the summer and then 5-10 during the winter. Allows the oil to warm and the block to normalize a bit. Gives your bearings time to warm up before they get beaten about as well.

    Just as important for a diesel is the cool down period after driving. You should idle a little once you arrive at your destination, get your things together, allow the heat to be distributed evenly about before you shut er down. Helps save the heads. This was a tip I learned from an old diesel mechanic. Obviously the about town stuff is less important than the heavy highway driving.

    Also if you loaded up, both the warmup and the cooldown are vital.
    • Re: diesel engine warm-up question

      Sun, August 20, 2006 - 6:43 PM
      First i’ve ever heard anything like this. My ’79 diesel is still purring along after more than a quarter decade and i’ve never once done a “cool down” as you describe. I always warm up my engine by idling for about 60 seconds, winter or summer, in our Pacific NW maritime climate. If the engine is still warm, i forgo the warm-up. On the coldest of winter days, i’ll idle a little extra if the engine doesn’t have a contented purr.

      Make sure you keep the engine oil level where it should be (neither too high nor too low), and keep it clean.
      • Typo

        Tue, August 29, 2006 - 9:51 AM
        I said after more than a quarter “decade.” Ha ha. Meant more than a quarter century!
    • Ken
      offline 0

      Re: diesel engine warm-up question

      Mon, February 5, 2007 - 6:35 AM
      Your reply was incorrect, don't take offense. I have a cummins diesel and when the temperatures falls in the single digits, cummins has a AC plug, right side below the head light, warm up times vary by temperature. I would think all diesel's would have this feature. Its in the manual. There are allot of benifits to the warm ups. like engine wear.

      If you need a websites to confirm this send me a message and I will reply back with the info.
  • Re: diesel engine warm-up question

    Mon, August 21, 2006 - 8:09 AM
    ive heard more about warm up than cool down too.

    hound tongue, im assuming you drive an old benz too? if so, is there a temperature / setting on the gauge you like the engine to be at before you drive?

    the thing i am curious about and dont understand is what the difference is between sitting and driving. i mean, obiviously the clutch is engaged, but on my benz, you can warm up faster by turning a knob that adjusts the idle, basically giving the engine more fuel. why not just drive at slow speed? if the engine needs to warm up, shouldnt doing a little work help? im not talking about getting on the highway, im talking a couple blocks of 1-20 mph. can anyone tell me if this is bad, and if so, why it is?
    • Unsu...

      Re: diesel engine warm-up question

      Mon, August 21, 2006 - 12:58 PM
      Nope, not an old benz, a chevy truck. It may be that the cool down is more important for the truck than a car, since it is usually doing more work to generate more heat, but I have heard the cool down aspect from a number of mechanics. As for what temp for the engine before I drive, it is usually just starting to register, like 160F or so.

      If you think of the aspect of how an engine operates under load versus no load, that will get you to the root of the warm up. Think of the fact that if you were to start a walk, and you stepped out your door after waking up and picked up a 40 lb sack and started walking. The possibility for injury is higher, than if you stepped outside and walked a bit and then picked up that 40 lb sack. For a small car, I would just start the engine, go back and get your cup of coffee or situate your stuff in your car, and then you would probably be ok in a warm climate.
      • Re: diesel engine warm-up question

        Mon, August 21, 2006 - 2:09 PM
        I have heard that relating to turbo-diesels but here is an article from Banks saying it’s not really necessary.


        MYTH #7
        You have to let a turbo-diesel idle for two minutes before you shut it off.
        This is a current myth that has a basis of fact stemming from many years ago. It also has a kernel of truth regarding today’s turbocharged gasoline engines that operate at higher peak exhaust temperatures than turbo-diesels. In the early days of turbochargers, the turbo shaft was supported by a babbitt bearing that could seize, or even melt, if the engine was shut off immediately after sustained boost conditions where the turbocharger would “heat soak”. A two minute cool down at idle allowed the turbocharger to dissipate any remaining spinning inertia, and the oil circulation cooled the bearing and prevented oil “coking” in the bearing area. Turbochargers haven’t used babbitt bearings for over 30 years, and today’s oils resist coking. Synthetic oils won’t coke, period. With a turbocharged gas engine, it’s still good insurance to let the engine idle for 30 seconds to a minute to allow the turbo or turbos to dissipate any inertia and to cool the bearing area to prevent oil coking, especially if the engine has been worked hard just prior to shut-down. Of course, using quality synthetic oil eliminates this potential coking problem.

        Today’s turbo-diesels are a different story. There is really no reason to “cool down” a turbo-diesel these days, but you won’t hurt anything by doing it either. You can still find people who swear you have to do it, but the myth is fading. Maybe they just like to sit and listen to the radio.
        • Re: diesel engine warm-up question

          Mon, August 21, 2006 - 2:39 PM
          yeah, ive read a lot of stuff like this and it only confused me more. mostly because im driving a 25 year old car.
          • Re: diesel engine warm-up question

            Mon, August 21, 2006 - 4:06 PM
            Well andy, let me see if I can clear it up for you.

            On a turbocharged vehicle, the turbo (exhaust powered air compressor) is cooled and lubricated by engine oil. Generally speaking if the engine has been run hard, the turbo is going to have alot of heat built up in it.

            Previously what has occured in some older diesels is that the non-synthetic oil that you use in your engine would have viscosity breakdown and what amounts to deep frying the oil. Basically the turbo gets gummed up with carbon from the oil burning up and degrading.

            The thinking behind keeping the engine running for a few minutes after hard service, is to allow the engine oil to continue to run through the engine. The oil being at a lower temperature then the turbo will absorb some of the heat and transfer it to the sump oil. The oil provides a cooling effect and lubricating effect.

            Now if you dont have a old school turbo diesel running on 80 weight, then running your engine for cool down is really not accomplishing anything. Unless of course you have a SVO Aux. fuel system and you are flushing your engine with diesel for shutdown, but thats something you can do in the final miles of travel.

            I'm not a real big advocate for idling diesel vehicles to warm them up. When possible I really do reccomend a engine block heater. One because it serves the purpose of getting the engine and seals up to temperature so little to no actual idle time is needed and also because it helps to improve the viscosity of the oil, so that the lubricating properties are not lost as much as they would be on a typical cold start. Putting your engine on a heavy duty timer, just an hour [or so depending on ambient temp] before you leave will greatly reduce your idle time and IMHO a better thing overall for the engine.
            • Re: diesel engine warm-up question

              Tue, August 29, 2006 - 10:39 AM
              thanks doc.. that was helpful but im still a bit comfused.

              we have a block heater, but its not easy to use as we park on the street, not in a garage. we usually warm up on a high idle for 3 minutes or so, more if we havent driven in a few days or if its really cold. however, sometimes we are running late and dont warm up as much as we should. id love to know more about what that does to an engine and why.. we have several blocks of low speed residential driving, where we can cruise at 15-20mph in first gear before we hit any real driving, does that make warming up while driving ok?
              • Re: diesel engine warm-up question

                Tue, August 29, 2006 - 3:08 PM
                Sure you are not hurting the engine.... well not really. Remember diesels run on compression (or the compression of air) not spark energy. The other thing is with cold fuel in a cold engine with cold engine oil, of course your engine is going to complain until it gets warmed up. You'll have crappy performance and you will make a lot of "steam".

                Several blocks of low speed driving will certainly help the engine to come up to operating temperature. More fuel = more heat. The biggest concern on adverse weather days is having the engine oil come up to termparture so it can do an adequate job. Traditional oil (as oppossed to synthetic which is contraindicated unless the engine has been completly rebuilt) even with a moderate addiive package cannot provide the engine complete protection until it gets up to temperature. Its one of the reasons why I am such a advocate for putting Lucas brand oil stabilizer in older diesels.

                It adds what I simply call a type of stickiness to the oil, that helps it both stick to metal surfaces AND lubricate. I know it sounds like a contradiction, but I've heard the difference this stuff makes on old worn out engines. As soon as i figure out a way to record the sounds from my engine stethoscope into a mp3 I will make a recordinng of the before and after sounds. It really it dramatic.

                Besides that and extreme tempartures (anything at freezing or below) the major difference between a cold diesel and one that has been on a block warmer, is performance during warm up and a ilttle engine wear. I wouldnt disagree with you if you wanted to do a high idle for a couple-few minutes before you got on the road. If for nothing else than to start to warm the block up and get the oil to a better viscosity for maximum engine protection.

                Personally I'm not a fan of idling any engine outside the realm of neccesisty. This is to say people with easy access to electricty and a block heater should do the air we breath a favour and use some of that "harmless" nuclear energy..... (note the sarcasm in that statement). But seriously if you live outside of an urban district and your idling your engine because you like the sound your cold diesel makes (then think of your neighbors) or perhaps you where born ignorant and don't care, but please get a block heater and a heavy duty timer.

                For those of you who dont know, EVERY engine manufacturer makes a block heater for youf vehicle and most can be purchased for less than $50.... just imagine the fuel savings you will have by reducing your idle startup idle time to nothing! Electricity is still cheaper than gas, and in the scale of things produces less pollution than idiling.

                So to wrap this up. In simple terms the bad things that happen to a cold diesel, are lack of performance, poor fuel combustion, poor fuel viscosity, poor engine oil viscosity, cold engine block, and generally sugglishness.... similar to what you experience after waking up the morning after a hard night of drinking. What happens when you drive a engine with tradtional oil in it too hard after a cold start is that you sacrifice the lubricating / protecting measures of the oil and whatever additive package, until the oil gets closer to operating tempature. The cold engine block hinders the ability of the engine to reach compression temperatures that are able to satisfy the diesels needs for complete combustion..... which instead of being expressed as voluptious black smoke is instead often expressed in the amount of condensate "steam" [or "fog"] that is present in the exhaust.

                Will it lead to catastrophie engine failure? Not likely. Accelerated engine wear.... over the life of the engine... things add up. Will driving slow while the engine warms up help. Sure. As I mentioned before. I'm not a real big fan of idiling a vehicle. I leave well before sunrise, [and in the days before my block heater] its was not uncommon for me to start the engine after a couple few cylces of glowplugs, let it get going for 30 seconds and let it high idle out of the neighborhood. By the time i reach the first traffic light, things are awake enough to work my way up to 80kph (50 mph). With the block heater I dont warm up at all. Of course on the tragically cold winter days, I have a fuel tank heater that I plug in as well.

                Why all this? Because it's a diesel not a gasoline engine. Anyone can drive gasoline. But it takes someone really special to drive biodiesel. Especially in the winter.
                • Re: diesel engine warm-up question

                  Tue, August 29, 2006 - 3:22 PM
                  <such a advocate for putting Lucas brand oil stabilizer in older diesels>

                  so we should be running this stuff, huh? where can we get it, is it readily availaible?

                  also, any suggestions on best oil to use in one of these old mercedes? both brand and weight/viscosity..
                  • This is the maximum depth. Additional responses will not be threaded.

                    Re: diesel engine warm-up question

                    Wed, August 30, 2006 - 3:14 PM


                    Yes it readily available in most coporate auto parts stores. If not there then any racing shop or truck stop should have it. Does it work. Absolutly!

                    I reccomend you use whatever weight of oil that your manual indicates. The engineers at Mercedes intended these engines to use this oil, using synthetic substitutes on non-completly rebuilt engines usually causes more problems than anything. To be more specific, the synthetic oil acts like a solvent. Freeing years of built up oil deposits, deposits that prevent oil from leaking out of ancient gaskets. This more slippery oil, often slips its way past piston rings and past valve guides, past gaskets and makes what was a previously well running engine into a basket case.

                    For old diesels most of the guys on the Mercedes forum swear by AMSOIL. I dont have an opinion either way. I spend my money on the oil additive and a good filter and change my oil when its due. Honestly any oil that is on-spec should do an adequate job of lubrication just so long as you dont exceed the oil intervals.

                    Past due oil will kill a Mercedes faster than anything else.

                    andy wrote:

                    <such a advocate for putting Lucas brand oil stabilizer in older diesels>

                    so we should be running this stuff, huh? where can we get it, is it readily availaible?

                    also, any suggestions on best oil to use in one of these old mercedes? both brand and weight/viscosity..
              • Re: diesel engine warm-up question

                Tue, August 29, 2006 - 3:11 PM
                OH yeah I should mention I block off 80% airflow in the winter to my radiator. Previuosly I have done this with my ghetto fabulous piece of diesel cardboard. But I paid one of my metal working buddies to make a nice chrome inserts covers to go in my grill to cover the cardboard.

                Chilling the air intake increases performance, chilling the radiator does not.
            • Re: diesel engine warm-up question

              Mon, February 12, 2007 - 5:19 PM
              I'll toss in what I know from the marine side of things:

              I've got an '85 Westerbeke, which like most sailboat diesels is based on a small tractor block. The manual says start it up, run under light load until the coolant temp is normal, after which time the engine load is unrestricted. They specifically say not to leave the engine idling for "any length of time". They don't say anything about letting the engine cool down before shutting it off. This is a non-turbo engine and is designed to run straight 30 weight oil.

              Running under a light load is a bit easier in a boat than a car (just set an appropriate RPM). My engine will go from a cold start to operating temperature under a light load in under 5 minutes.

              A friend has a 10-year old Universal (same block) and the manual says basically the same thing.

              Yanmar specifically says to avoid idling their current engines for more than 2 minutes regardless of temperature, which can occasionally present a bit of a challenge.

              The only place I can see idling after running being important is in a raw-water cooled engine (some older volvo saildrives are like this) where you want any hotspots in the cooling galleries to dissapate before shutdown to avoid salt builup. This obviously isn't going to be a problem in a car.
              • Re: diesel engine warm-up question

                Tue, February 13, 2007 - 1:20 AM
                Correctamundo, some diesels are not good for idling, especially because it causes excessive oil consumption and for some engines can develop hot spots because the waterpump is not operating at optimal RPM.

                HOWEVER I'd say 90% of most vintage diesels in the passenger market dont have a "high idle" or "pto trim", let alone the ability to set the engine at a higher idle without the transmission engaged or pulling against a mooring or anchor to warm the engine. Now some do have a high idle switch and this is one of the two times this switch is usually indicated.

                Honestly I'm a huge proponent of Engine Block Heaters and the like to reduce or eliminate the need for cold idling of diesels, HOWEVER in the abscence of a block heater, high idle capability or other manual proscribed technique, idling is absolutly essential to get the engine up to operating temperatures before placing the engine under a real load.

                Now this is typically only necessary on a cold diesel and really only during winter conditions. What idling or warming up the engine does is gets the engine sump oil from something less like molasses to something more like a meduim that has to maintain a lubricating property down to .0001" film surface. This is especially important for single weight mineral oils such as those used in older marine diesels. Warm oil protects bearings, piston rings and valve seals, for turbos its reduces the damage that comes from contraction of cold precision parts in close contact and essentially hyrdroplanes the contact surfaces and in the injection pump it allows fuel to recirculate through the filters and tank(s) to bring it up to temp and improve its viscosity so that that the lift pump and injection pumps dont have to work so hard.

                Idling a engine thats made to be run at 100% duty cycle or to be off can cause early demise of wear parts. However their are diesels especially in the passenger market that are capable of being idled during regular use that dont necessarily see any expedited detorioration.

                I have a 36 year old diesel that will growl like an old man on a cold day if I dont let it warm up proper. Since it's a german design (basically a tractor) I have a hand pto trim that allows me to idle the engine higher then the normal closed position, if I really want to get creative I can set the exhaust brake to partially closed and let those exhaust gasses build up in the manifold to heat things up a little faster. I'm not a big fan of concentrated cold diesel fumes though.
            • Unsu...

              Re: diesel engine warm-up question

              Mon, February 26, 2007 - 8:28 AM
              Please define:

              'old': is this 20 years, 30 years, what?

              'cold': what sort of ambient temperatures (Fahrenheit) are we talking about? 20s, 40s, 60s? I'm in coastal MS. Winter lows are minima mid 20's. Spring lows in the 40s. Well, summer, naw I an't EVEN thinking about idling or block heating, right?
      • Re: diesel engine warm-up question

        Mon, February 5, 2007 - 7:05 PM
        > As for what temp for the engine before I drive, it is
        > usually just starting to register, like 160F or so.

        Ditto - I don't move in the winter until the temp needle does. In the summer time, it usually isn't much of an issue, though.
        • Re: diesel engine warm-up question

          Wed, February 7, 2007 - 12:42 AM
          correct most vitage diesels running on non-sythetic fuel require at least 5 mins of warmup for the engine oil, older diesels require longer warmpup periods to include several minutes at low speeds before the drivetrain is anywhere near highway speeds. Not to say they will not run under less than ideal conditions, however it will cost you machine life in the long run.
          • Re: diesel engine warm-up question

            Wed, February 7, 2007 - 12:42 AM
            vitage = vintage
            • Re: diesel engine warm-up question

              Wed, February 7, 2007 - 1:15 PM
              How does the fuel affect oil armup times?
              I find starting a disel on 90+% gasoline, it doesn't warmup any faster. It just starts trying to run backwards once it does.

              I believe the Don't drive at all warmup theroy comes from back in the day of carburetors, and primitive timing controls giving poor driveability cold.
              Nowadays most manufacturers recomend driving easily for the first few minutes....Partly because computerised engine controls have eliminated that driveability issue, and partly to keep emisisons down.
              • Re: diesel engine warm-up question

                Thu, February 8, 2007 - 10:26 AM
                typing while tired.
                Non-synthetic engine oil is what I meant to say. 90% gasoline in your diesel? Thats ill advised. The fuel oil of diesel has lubricating properties that are necessary to keep you injection pump in good working order. Running concentrations of gasoline through the pump could lead to premature failure.

                The warmup "theory" for diesels is important because the engine oil does not flow well when cold. Poor flowing oil has reduced lubrication properties and will lead to faster engine wear or other problems. Diesel engines do no make the same amount of heat as their gasoline cousins, therefore they take longer to heat up. Basically running the engine hard during warmup periods can change the additive package of the oil into more of a varnish then a lubricant.

                Newer passenger car diesels utlilize the glowplug system to assist in warming the engine after ignition and different fuel spray patterns to help warm the engine up and minimize the amount of unburned fuel that leaves the tailpipe on coldstarts. For an engine that designed to run without or with minimal warmup times then certainly you can go with whatever the manufacturer recommends for that model year. Just dont expect that you'll be able to treat a 34 year old diesel the same as one you bought last year.

                I'm not going to comment on petrol engine technology as its not really relevant to this topic. As far as driveability is concerned a warm diesel combust fuel better than a cold diesel. Considering they dont run as hot as their petrol cousins and (for the most part dont have spark plugs) they have alot more mass to warm. A cold diesel is not combusting the fuel properly and completly so yes their is some lack of peformance. Which is why you'll see large diesels with cardboard or vinyl flaps on the front of the engine cowl to limit the amount of cold air that goes into the engine cooling system.

                One of the test questions for the CDL includes a question about the minimum warmup time for diesel engines.

                Anyways their are no absolutes, especially with new techologies in use for passenger vehicles. For anything Medium Duty on up the rules change significantly. I get to operate diesels of all sizes and vintages and each one has their own quirks advantages and disadvantages.
                99% of them require warmup time during adverse weather temps. Of that 1% that doesnt technically require a warmup period, it still runs better after it has had time to warmup.

                I'll go deeper into what happens to a diesel in the cold and why its good to warm them up later. I gotta run now.
                • Re: diesel engine warm-up question

                  Thu, February 8, 2007 - 1:35 PM
                  I thought it might be something like that, normaly your posts make a lot of sense to me.
                  90%, yeah I think so. My frids car came back on a tow truck after blowing the head gasket.
                  I put in a used engine for him, and it fired right up. Ran good with little smoke. After maybe 10-15 minutes it started knocking and clanking, so we shut it down. After awhile looking and finding nothing wrong, loose, or stray in the engine compartment , we tried again, and got a perfect start, folowed a few minutes later by bad noise. The pattern we found was the car ran fine tilll itgot warm enough not to trip the glow plugs, and at about that temp, preignition would start the bucking and clanking agin. A sniff test revealed gasoline flavor, and draining the tank solved the problem. THe stuff we drained out ran OK in my gas truck, so It had to be pretty straigt gas. Seems no permanent harm was done. Our conclusion was in the heat of the moment, the wife had filled the tank with gas, hoping her problem was with fuel delivery. I think in So Cal, they sometimes use a green hose for gas, and it is always diesel here.

                  It doesn't always turn out so well. I was at the wrecking yard, and the manager knowing I always buy the diesel stuff asked if I'd be interested in helping them start a 7.3 Ford that had come in with gas in the tank.
                  hooked up a diesel can as fuel supply, drained and filled the filer with eisel, purged the lift pump, injector pump, and lines.
                  It took a lot of cranking to get going, likely the ends of the glow plugs blown apart.
                  Once it fired, it ran rough and needed pfdal input to keep runing. there wa s a lot of engine knock. Rod bearings?
                  Less than 10 minutes later, BANG! Whacka, Whacka, Whacka stop.
                  I think it was a broken rod or crank.
                  My guess is the driver had filled with gas, over 50% mix, and drove on the freeway untill the engine stopped turning, and it was already toast when I got to it.

                  Little off topic, but good times!

                  My favorite warmup scenario is to live on a hill where I can roll start if I have to, and drive gently downhill to warm up (idling isn't the greatest thing for engines, or neighbors) . Returning home from the other direction where I can roll downhill for 3 minutes to cooldown.
                  We can all dream right?
  • Re: diesel engine warm-up question

    Sun, February 25, 2007 - 10:34 PM

    Well, "here" is a great way to create a disturbance ! open a
    discussion about idling a Diesel…. I am going to post this, and run away !!! you guys can fight it out. I think, (as I look back over a lot of years) at wearing different hats in the engine and Diesel field, there never was a more controversial, argued about, opinionated, and mis-understood area in our diesel history than idling…(maybe engine oil second). Firstly, let's define the term…we are talking unloaded, static, idle (500-650 RPM)– like you can see at any truck stop, or freight dock, bus garage, construction jobsite, fish harbor, even rail yard, or tug yard. There they sit… all day, maybe all night long- 10 below, to 115 degree days, hour after hour, … idling. Whether it is a Detroit 2 cycle, or other 4 cycle…. Is immaterial, it is part of the "tradition", the folk lore, the "everybody does it" thing, you sleep and keep warm, or run the air conditioner, go eat, or
    wait to get loaded, or move on the next pile…attended/ unattended… just
    let it idle. "Never shut a Diesel down"… I had more than one fleet
    manager proudly announce to me (emphatically !) that "our engines are "never" shut down-except to change oil or repair" ; a Greyhound shop manager proudly showed me three starters on the floor that were just rebuilt…and proclaimed, "next time we do filters we "have" to put those starters back on !….of course our units are NEVER shut down, so it doesn't really matter !" Let me bore you with "my" prospective, We can start maybe "during" the 1930's…. Diesel engines were simple, and, we really knew little engine-wise, engines were primitive because of the materials we had available, our machining/fabricati on abilities were ungroomed, and our storage battery situation was "comical" (wood cases/tar/ low voltage, what's a cranking amp anyway ?) ; these balky engines barely knew what an "atomized" spray was… fuels were , well, fuels ! and, engines still had torching grids or crosses cast into them for torch heating, pony motors were everywhere (you took them into your motel room), and, charcoal tray oil pan holders were commonplace… gasoline on a rag and ether bottles, primer valves and spark plug fired gasoline blast intake manifolds, propane, and
    compression release devices of many "wild" designs, tow hooks mounted on everything, and even , truck mounted super heated alcohol/coolant pump rigs (that was our anti freeze back then) to drain cold and re fill hot. On any given morning, just getting started was a tribulation…in the Anarctic, St. Louis, or the hot deserts of Mexico….Once started ("if" you got it started), never shut it down. !!! Even after a half days work, given a few hours off, a restart was no guarantee (without a fight). For all of the Diesel engine improvements … after WW ll there was very little changed, when trucks began cross country routes and Diesel
    became part of our "lifeline," things slowly changed, by the mid
    1950's we had developed "decent" storage batteries and electrics, and,
    engines were much more sophisticated, fuels were optimized and
    constant, and we had cold start aids that worked. Times had changed.
    I have to say, that by the 1960's …essentially Diesel "things" were about like they are today-; automobiles and Diesel trucks were safely "stop and go" entities. (other than the usual poorly maintained, junkers, and obsolete that always exist), what we knew back then was virtually–what we know today. DO NOT IDLE YOUR DIESEL !There, I said it ! I attended months of (factory) schools on Hercules, DD, and Cummins, then later went corporate with bigger engines,but, the knowledge was the same-universally- During the 1950's cam ground (gas/diesel) piston designs came into vogue; measuring a room temperature piston was a shock ! It was not round, and it was not the same dimension top to bottom; …those clever designers were tired of fighting over-temp seizures and start-up chaffing, so they designed pistons to not be shaped like pistons until they reached around 140 degree water temperature…lay your micrometers on a hot piston and it "was" what you expected. At below 140 degree water temp things went backwards though…as the piston returned to its cam ground specs it allowed air and fuel to sneak into the crankcase, and the piston itself , now not fitting the bore, sorta' wobbled…in doing so, it .makes the rings chatter, and, with the added air and fuel residues things were not good in cylinder-ville. Issues on block expansion, gasket pinch, and lube oil adequacy all played in at lower temp. as well These phenomena were much enhanced on a diesel vs. gasoline engines, firstly, there is just a heavier, less evaporative fuel, lower air flows impair atomization, diesel fuel likes engine oil, and diesels over cool the combustion chamber (no butterfly, higher capacity cooling system) anyway. As a warranty guy, I could tour truck stops and see rigs in Bozeman, Augusta, or Fairbanks at 0600 with a lake of raw fuel and oil underneath…having seeped through the pipes and over flowing the dipstick tube from a over full crankcase on still-idleing trucks, water temperatures at unreadable guage bottom (60 degrees) was more, MORE than common, 90 degrees was a hot one ! if it broke 100 she was a scorcher. Oil samples taken were dilution disgusting, yet the driver would wake up, and hit the road for a 300 mile power jaunt. Turbochargers were coming into vogue, and engine clearances and tolerances were getting pretty tight, we had "o"-ringed liners, and cooling systems that caused aeration pitting, our fuels were "cut" in winter, and, the times and machinery had simply changed … the excuses and reasons for idling were now in all the past, obsoleted, and non applicable. I was leaving Chicago late at night, for Cleveland after one of those 12" Chi-town snow storms hit (quick), and locked the city up…As I stumbled into Gary (where the truck stops are kinda grouped), all the
    lots were full of trucks…thousands , who had gathered there at dusk
    when the ugly started falling, at 2AM it was cold, and white er, white smoke I mean… the place looked like a hot tub in Minnesota ! As I parked the air was heavy and actually oily, the smell was really severe, as I walked through the rows and rows of rigs, I wondered how the sleepers did not smell this borderline noxious unburned fuel vapor. In 1965 there were three big Gary area stops, I went to all three…. I had seen a couple of our "house account" company rigs in there, so I took the time to call them for a scenario the next day….4PM most began assembling, after the word got passed to get off the road…9-10 AM the
    plows were done, and things began rolling again… 18 hours ! of idle.
    I began addressing this issue with test cell and shop people, reviewed teardown histories/stories/ theories, and spread the word to our shops for the next "day after" the storm, new arrivals to our shops, to check dilution (dipstick filter paper) and send me the sheets (Shell oil had a test kit out back then)…the next spring, I
    reviewed and assembled all this info into a paper. I learned that, as long as the water temp stayed "above" 140, idle your heart out ! once below that, or, into white smoke, fuel-oil dilution, turbo damage, piston score, and bottom end squeaking, and shortened engine life were imminent…plus, there goes your warranty. Diesel Engine companies were all fighting the same problems in the mid-1960's, idling was one of them ! secure hand throttles could hold your RPM to turbo cut-in point, or, cylinder temperatures where the coolant did not drop below 140 (especially with winter fronts/shutters and the sound deadening on a modern truck, but, this meaqnt you were up around 1,000/1,100 RPM !… and, as ambient temperatures changed, a hand throttle was not a very stable thing. With residents complaining (firstly about diesel smoke-then engine noise) truck stops started adding plug ins for engine heaters, the mantra at all the factories was in unison though… "do not idle at temperatures below 140 degrees !" My co trainer friends over at Detroit Diesel, and Caterpillar told the same story as we did at Cummins…, we all had a problem !! Stewart-Stevenson down in Texas did a big write up on DD idle problematics- I wish I still had a copy (got one ?) it was written in oil field language and perhaps more severe than even the "factory" stance on idleing . I can remember to this day, in conducting driver or mechanic classes, the blank looks on the faces when I would say "One more time …Do not idle a diesel … uNLESS …you keep the water temperature above 140 degrees ! there are no exceptions. This is not 1948 !. " But, here we are almost sixty years later….. and …., There really is a glut more to say on this subject, especially of a technical nature, but, I will let the posters say it. So, let the dialog begin !!!! "I" am going on vacation for a week or two. peterB H8H-649-190 http://doowopcruise r.blogspot. com
    • Re: diesel engine warm-up question

      Mon, February 26, 2007 - 2:27 PM
      Interesting write up, but it doesnt really address the issue at hand here.

      The original topic was idling for warmup. And unless you have a *newer* as defined by an engine have electronic or electro-mechanical devices that reduce the amount of warmup time necessary before the rig is ready for full power.

      Why because a cold diesel doesn't burn fuel well and unburnt fuel not only pollutes, but its a waste of energy. On engines with fuel filter recirculating return loops it actually runs the excess fuel from the injector back through the fuel filters instead of returning to the tank, this heats the fuel filters up and improves flow. For engine sump oil (since most ppl do not run synthetic) it allows the oil to improve its viscosity. Also remember that even in winter blends of diesel fuel, the viscosity improves significantly when warm, that return line goes to the tank to heat the fuel up their as well.

      Cold diesels in hostile climates, like Alaska or the Antarctic among two popular places are often not shut down unless the operator has a diesel co generator on board which can provide electricity for the sleeper cabin, battery heaters and charging circuits, heat for the cabin & and engine. Modern day diesels without cogenerators are often equipped with electric actuators called "hi-idlers" that bring the engine up to proper idle speed this is more or less a simple device very similar to a cruise control, this provides optimum RPM for the engine powered generator that powers the things in the sleeper cab as well as keep the water pump sped up and provides heat or AC which may or may not be auxiliary units. The highest tech item out their currently is what is commonly called an load management system which analyzes the amount of energy being consumed, engine temp, amp in current and battery voltage and adjust the engine idle accordingly.

      As I've mentioned before I am not a big fan of idling for warmup I really do prefer that folks use engine block heaters to preheat their vehicles so they can get up to operating temperature faster. Some newer commercial and non-commercial diesels are also equipped with glow controllers and glow plugs that are capable of keeping the plugs on for a proscribed period after the engine has turned over, this is to aid the engine in getting up to operating temperature and to reduce fuel lost to incomplete combustion/pollution.

      My 30 year old Mercedes is actually equipped with what basically translates to an ether pump to help get it started during extreme cold weather. But even then the operators manual indicates a warmup period at a higher idle (using the hand throttle) for certain periods depending on how cold the weather is. Of course my engine is also made for single weight oil as well so if I want to keep it running I will follow the directions of the genius engineers who built my engine and not someones opinion.

      While every engine is different and their is no one *RIGHT* way to do things especially with the advances in engine design in the past 30 years I will say that unless you have some super engine block heater, you will either need to let your engine warmup by idling or take it easy until it gets their. Its called operating temperature for a reason.
      • Re: diesel engine warm-up question

        Mon, February 26, 2007 - 4:17 PM
        A thermostat should keep your car over 170F in all operating conditions, and running without one is asking for trouble. If you are somewhere overcooing is still a factor, covering half your radiator with tinfoil or something is easy to do.

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