scottybdiving

I found this article interesting and agree with most of it. This is a common practice in the commercial and industrial workplace and it has done well for me.

Diesel or Gas?

Over and over I see people driving diesel power vehicles who just happen to be the worst kind of people who should be driving them. Like the time I was at a welding supply shop gathering materials for my contraption and a customer who walked in asked me if the new truck outside with the Cummins engine was mine. He asked if it smoked when it was cold. I said not any more than it should. He seemed concerned and said his made excessive black smoke when it was cold and he rev'd it up to 2,300 to 2,500 R.P.M.s'.

When I heard that, I thought to myself, what a dumb ****, the engine even has a governor on it so that it won’t even go any higher than that so he must be flooring it when it’s still cold. I let the guy walk away without knowing how I felt. As soon as he was out the door I said to the guys, “Yeah rap that baby up while it’s cold, and dilute you motor oil with diesel every morning. That should make the engine last along time. I bet if he keeps that up; the cylinders will be gazed before the engine is even broke in.”

Guys like him don’t realize and understand the difference in the way diesel engines should be operated. Compared to a gasoline engine, there are some major differences in the way the fuel is consumed. When cold, diesel engines do not burn fuel nearly as efficient as gasoline engines. Diesel fuel has a higher flash point and requires a higher temperature to ignite to create combustion. Diesel engines also require more compression than gasoline engines.

At the start; a diesel engine requires high compression or a pre-heater, or both. To burn the diesel fuel efficiently, the whole engine has to achieve its required heat range.

Therefore a person who operates a diesel engine should be more patient than one who drives a gasoline engine; especially when it comes to starting out their commute. The deal is that if the diesel engine doesn’t get a chance to warm up, the fuel doesn’t get burned thoroughly and since it is more or less a solvent type of oil, it will wash through the piston rings and dilute the oil within the compression rings on the pistons and enter crank case. Unburned diesel can dilute the lubricating oil within engine’s crank case and that’s not a good thing.

In a way diesel engines are like horses. As they say, you should walk a horse after running them before you putting them in their stall. Or as they say: you don’t want to put them away wet.

I’ll have to give my Dad the credit in this segment:

He said that the City of Tacoma’s was having troubles with losing the turbochargers on its Transit Buses. They figured out that the problem was that at the end of the shifts, when the buses were driven into the garage, the drivers would turn off the engines so that the exhaust fumes wouldn’t accumulate in the garage.

The thing is: turbochargers spin at about 50,000 RPMs' and when the engine is shut down the oil pressure drops and the bearings within the turbos loose their supply of oil as they spin to a stop moments later. The Transit Department figured out the solution was to tell their drivers to let the engines idle down for at least a minute before turning them off. That way, the turbos have a chance to slow down a bit before the oil pressure supply drops off. That was the end of the problem with turbochargers going out.

It’s a good idea to let any water cooled engine idle awhile before shutting it down because the water circulating through the engine block does not have a cooling affect if it isn’t moving. Right after an engine is shut down, the water temperature within the engine block escalates because it absorbs the heat from the heads and cylinder jackets. With no where to go; the heat builds up in the entire engine. This excessive heat build up is the cause of many cylinder heads being warped. (Blown head gaskets, warped manifolds, water in the oil, you name it.) So if you like going through engines – rev it why don’t you.

neodoc

Scotty, this is a great post. I remember when I got my first car, a 1985 Isuzu Impulse Turbo, I was told by a mechanic to let the engine idle a bit before shutting it down. In the almost four years I had that car, I would always coast home for a block or two and let it idle some more while I got out to open the gate. I never had a problem with the turbo. The engine block did develop a coolant leak at the end, but I truly think it was because in that type of vehicle, the engine block wasn't designed to handle the higher pressures of the turbo. After all, it was an Isuzu, and it was the first year they had come out with the Turbo. In comparison to the standard Impulse, which was very slow, this one had a lot of power, or at least I thought so at age 17. It was a beautiful car, and I still have the brochure from when it was new. Ahh, memories. Anyhow, I agree with your post that any engine needs to properly warm up before it's put through its paces. My CLK when cold actually holds the lower gears longer before it upshifts, to help warm up the engine. The CL63 has a colorized oil temp readout that is blue when the temp is still below optimal. Having had cars in my family that have been driven over 100K miles, I'm a big supporter of treating the engine well. If you do, you get the reward of many miles of service and some big grins when you give it a flogging. Good work.

tm4exc

Actually MB has a higher RPM Shift points on cold gasoline engines as they want it to warm up fast to increase the early in the drive cycle effectiveness of the catalytic converter. This was true even on my 97 E320 which has 121K on it and still going strong! Absolute believer of the cooldown process though with a minimum of a 60 sec idle at home outside the garage before she is put to bed.

BJ021

Great post Scotty. My old man had diesels in North Dakota and he always gave them time to warm up and rarely had an issue. There is no colder place in the country - and he always got good service out of his diesels because of his careful attention to the engine. Not sure if he let them idle down, but he was not a very aggressive driver, so I'm sure the engines had time to cool down.

I on the other hand am a little more demanding of my cars, so I'll have to "idle" into the 'hood and let it run a bit before shutting it down.

jongaines

Scotty, there is a screen on the multi-function display which displays engine temperature. Is there a temperature that should be reached before "pulling out" to allow proper engine heating on the 320?

scottybdiving

The only information I can find is from International Truck Engines (Powerstroke). They recommend 160 F (70 C). I have always started the truck, walked in to re-fill coffe and grab a few things, then drive just above an idle up my driveway, which is 3/8 mile. By that time it sounds happy when I pull out into traffic.

infamily

I live in MN and even in garage it can take long time for car to heat up.. cool down is never a problem in MN . Thank you for your post. I happened to be reading your post when my wife was getting ready to hop in her GL 320. I shared your post and sure enough she started the GL and then came back in to gather her stuff. Thanks a bunch for helping us prolong the use of our car.

StevethePilot

I did wonder about the spin-down time for the turbo, as when I'm flying a Turbo 182 the instructions are to idle the engine for approximately 5 minutes before shutting down, to avoid thermal shock on the turbocharger. But why aren't there specific instructions on Mercedes' CDI engines regarding warmup and idle for spin-down?

jongaines

Thanks. It will take a while even in NC temperatures for the engine to get that warm in the winter; probably at least 5-7 minutes.

lkchris

Interesting information.

Of course little of it is applicable to CDI Mercedes, but interesting nonetheless.

The Mercedes engine, being electronically controlled, isn't going to overfuel ever.

The reason diesels don't warm up by idling is because--unlike gasoline engines that run at 15.7-1 air/fuel ratio (stoichiometric ratio) at all speeds--a diesel engine's air/fuel ratio varies by engine speed and at idle the ratio is something like 150-1 meaning the engine's hardly burning any fuel at all meaning it's hardly generating any heat. Just start it and drive away.

scottybdiving

It's not a matter of overfueling more like a matter of efficient combustion of the fuel. To say a diesel will not warm up by idling is inaccurate. Yes, they will not warm up as quickly as a gas engine because of the manner that ambient air enters the engine. Nonetheless, an acceptable temperature can be achieved by idling and this is not only recommended by most diesel engine manufacturers, it is a widely accepted practice in industries that utilize diesel engines commercially. This includes Caterpillar, Volvo, Komatsu, John Deere, and many others.

Jlight

In our diesel boat we always allow the engines to idle, never "start and go." We also allow for a 5/10 minute cool down that after running hard and shutting down.

I can't imagine "start and go" on any vehicle/engine...

lkchris

Despite the fact it's what EVERY auto manufacturer recommends?

Jlight

Yes despite the fact thats what the OEM's say I don't think I would push any diesel engine super hard on start up. That's just me, perhaps mis-informed but stuck in my ways

scottybdiving

Fighting the Cold
Jan 1, 2003 12:00 PM

FRIGID winter months are here, and colder weather on your skin means tougher conditions for diesel engines.

Whether it is simply trying to move a customer's truck into a service bay on a frosty morning or operating your own truck through the winter, International Truck and Engine Corporation offers the following guidelines for starting, warming up, and running diesel engines in cold weather to achieve better engine performance and extend engine lifecycle.

When the thermometer dips into the teens, begin using the proper cold-starting aids to get the best performance out of engines. These aids include glow plugs, block heaters, ether kits, and oil pan heaters. It's important to know which aids to use and follow the manufacturers' recommendations for the application and engine to ensure smooth starting and to avoid damage.

Glow plugs, which are standard on International T 444E, International VT 365, and Power Stroke diesel engines, are used to raise the temperature in the combustion chamber to aid cold engine starting. Because glow plugs enable engines to start instantaneously, no other starting aid is necessary down to -20°F and below.

In addition to standard glow plugs, International recommends using block heaters to raise the temperature of the coolant surrounding the cylinders and improve startability. A block heater can be activated as soon as the engine is shut down to prevent rapid cooling of the engine. All International engines can be equipped with block heaters for starting at temperatures below -20°F.

For temperatures below 10°F, International in-line, six-cylinder engines require an ether kit to start, as they do not come equipped with glow plugs (ether should never be used on the International T 444E or International VT 365). Ether kits inject a specific amount of ether into the intake manifold to ensure starting.

Be aware that ether is an extremely flammable material. It must not be used with the cold start and warm-up aid kit, which is recommended and approved for use only on mechanical engines (a fuel-fired flame preheats intake air). The cold start and warm-up kit is an alternative to ether on mechanical engines as a starting aid. It improves cold starting and minimizes white smoke.

When the temperature plummets below -20°F, an oil pan heater will aid cold starting and alleviate stall problems that can occur in frigid temperatures. Oil pan heating elements warm the temperature of the engine oil in the sump, improving its flow to ensure an uninterrupted supply of oil to the injector and other components. International in-line, six cylinder engines have oil pans designed with a heater plug port to better facilitate installation of the optional oil pan heater.

Engine warm-up
Once started, diesel engines need to be warmed-up in order to raise the coolant to an operational temperature of 160°F, preventing potential engine damage and enhancing performance. Warm-up aids include Cold Ambient Protection (CAP) — the hand throttle and an engine warm-up device. Standard on all International engines, CAP slowly increases engine idle speed to a preset maximum rpm to speed warm-up time. The CAP feature is automatically enabled when the intake air temperature is below freezing and coolant temperature is below 149°F for the International I-6 or 158°F for the V-8.

The hand throttle is standard on all electronic engines and sold separately for mechanical engines. It is used to manually raise engine idle speed to maintain coolant temperature and is operated by the driver of the vehicle. Newer electronic engines equipped with CAP minimize the need for hand throttle. However, hand throttle use is required on mechanical engines from 10°F and below.

Some diesels, including the International T 444E and International VT 365 engines, have an available engine warm-up device. Used as an exhaust system restrictor to increase load on the engine, the engine warm-up device speeds cab warm-up and reduces white smoke.

“Many truck owners overlook the importance of not only properly warming-up their diesel engines but guarding against extended idling and rapid cool downs to maximize their engine performance in cold weather,” says John Kemmet, manager, field service, International Truck and Engine Corporation. “In the winter months, it's vital for engine components to reach and maintain proper temperatures for operation to reduce risk of damage to engines, and in the end, keep trucks on the road.”

Once the engine is warmed-up to a temperature of 160°F, the engine must maintain this temperature, enabling the engine to run smoothly and adequately heat its truck cab. At this temperature, the coolant will keep the areas surrounding the cylinders warm enough to ensure complete combustion of the engine's fuel and air mixture. Complete combustion aids in reducing the accumulation of excessive carbon deposits on valve stems and guides.

An on/off fan and underhood air valve can also be used to maintain coolant temperature. On/off fans reduce air movement to help maintain adequate engine operating temperatures, and are recommended in temperatures dropping below -20°F to reduce air movement. Viscous fans often rotate at too high a rate of speed even in cold temperatures and thereby remove necessary heat from the engine by cooling the intake air. An on/off fan prevents this by rotating at higher RPMs only when cold air is needed.

Underhood air valves warm the air entering the engine by blocking the air inlet, taking warm air instead from under the hood. This needs to be used in vehicles where extended periods of idling cannot be avoided or for vehicles required to idle between stops. An underhood valve also prevents snow from blocking the air intake.

Cold weather checklist
In the transportation industry, it is vital to keep moving even under harsh weather conditions. To minimize problems, frequent maintenance is required in extremely cold temperatures. Following this checklist will help avoid unnecessary damage to the engine:


Check all rubber parts (hoses, fan belts) on a weekly basis.

Check all electrical wiring and connections for any frays or damaged insulation. Keep batteries fully charged and warm.

Keep tanks as full as possible to prevent condensation on exposed tank walls. Fill fuel tank when engine will be shut off for eight hours or more.

Check air cleaners and air inlet daily, or as necessary, when working in snow. An underhood air valve can also be used to ensure that snow and ice will not block air inlet.

Diesel engines require different grades of fuel during extremely cold weather. In temperatures below 20°F, use diesel fuel No. 1 or DF1, or diesel fuel No. 2 or DF2. Either fuel should have a minimum cetane rating of 45. When confronted with severe arctic cold weather conditions where the pour point of fuel requires low cetane, additives are required to supplement the fuel. Fuel suppliers or International dealers should be consulted.

BOYRACER

....hahaha, got you beat! It's waaaaaaay colder here in Alberta, Canada come January to March! LOL

And, as for Scott saying to cool the engine or idle it after a run, so true! My '87 300DT is absolutely minty and the mechanics at the dealership ask if at any point I'd sell it, I'm to let them know! As the diesel engine has to be taken care of and patience at your initial start up!

peace

BJ021

Ahhh, the origin of the Alberta Clipper! Nice! Did you play hockey outside 3 months of the year like we did growing up?

irishcg

I find this funny as a fairly new diesel Mercedes owner. I purchased my E300D a few months back and it was in spectacular condition. The owner advised me to warm it up every morning prior to driving, he gave the same reasoning as posted by Scotty. Later I posted a question on another MB diesel forum asking how long I should let it idle before driving. Every reply was the same, no one warmed up their cars, they just started and drove off. I guess that I trusted the previous owner of my car much more than the self proclaimed experts, as I continue to warm it up. Thank you for posting and justifying my behavior.

lkchris

Welcome to 1955.

StevethePilot

Okay, so warming it up may not be that important (though I do wait for the glowing yellow spring to turn off before starting it up), but with my experience with air-cooled turbocharged aircraft engines I thought it might be a good idea to idle for a couple of minutes before shutting down the engine on my liquid cooled GL320. So I pull into the garage and of course for safety's sake I shut the door, and just wait for three or four minutes.

scottybdiving

Now that's funny right there, I don't care who you are.

StevethePilot

Good to know SOMEBODY reads my posts!

Git er done!

gas-man

I have been reading this thread and again each side have good reason for suggesting what they usually do. This question is also tru to gas engines not only to diesel, to warm up or not. I guess to each his own.
I belong to the warm up group. ever since I have learned to drive and owned my cars I want them to last as long as it can, maximize its potential. I have owned cars that have outlasted their comparisons.( 1981 300 SD=420,000miles sold, 1989 300 SDL=>350,000 miles traded-in, 1991 190E 2.6 >180,000 miles traded in, 1999 ML 430 =>200,000 miles and still running). Even my Domestic, a 1998 Chevy Astro van conversion lasted me >170,000 miles and is still going as my uncle told me. So I am quite happy warming up my cars for at least 3-5 minutes if it will give me peace of mind. I am not an expert if it will benefit the engine or not especially the new engines but for my peace of mind. Back in the Philippines where the weather is warm and diesel are popular ( about 60-70 % of cars and trucks) they all warm up their engine.
I always think of well trained athletes they usually warm up and stretch before they run a mile or 26 miles.

StevethePilot

Interestingly, without ever warming it up I drove my LX470 217,000+ miles and got comments from the mechanic on how good my engine not only ran but looked after that amount of time (no buildup on the valves, everything very clean, very little wear). I think the idea of warming up for engines has come and gone as modern engines are computer controlled and built to much more exacting tolerances.

I was also reading an article that suggested the stretching warmup and stretching cool down for atheletes is now in question as to whether it's even bad for you. Of course, that's one article in one place, but still the idea exists.

alx

interesting post.

however, somewhat misleading and outdated...

the turbo spin-down time applies mostly to large turbo applications running hot oil and getting turned off after spirited driving. think supras with t66, t88 and the like turbos, skylines, eclipses, etc. there is even a widget called "turbo timer" that will keep the engine running for predetermined time (usually few minutes) after you lock you car and walk away...

however, in a normal non-tuned engine waiting for a turbo spin-down to avoid oil cooking the turbo axle is somewhat of an overkill..

the oil cooking is a real danger mostly to regular turbos where the turbine axle "skates" on a thin film of oil. however, nowadays most turbos are ball-bearing based and as such one has to really run hard the vehicle in a hot day and then shut it down instantly to cook the bearings.

the rest of the post- absolutely agree- the diesel when fired cold needs to be left alone for a minute or two to reach some intake temperature so the diesel fuel atomization is more complete and the burn process - complete.

alex