I came up around farm diesels. I was taught to ALWAYS warm them up before putting them to work, always run them for few minutes of cool down on hot days before shutting them down, and leave them running if you will need it again within the next 30 min.

I find myself trying to lock up my 240 and leave it running while I run into the store. Am I helping/hurting the longevity of the engine or just wasting my time?

It is not necessary to allow the engine to warm before starting off, as well as leaving it running for a while prior to shutting it down.

The best method to warm an MB diesel engine is to drive off as soon as oil pressure builds. I'm not advocating flooring it from the start, but driving off easily until the engine reaches proper temp. Heat is generated through the combustion process. Loading the engine allows it to get to operating temperature more quickly. It would take several minutes for the engine to get off the peg at idle. You would actually be doing harm to the engine by letting it idle for long periods of time. MB recommends shutting the engine down and restarting if the engine will be at idle for periods longer than 1-2 minutes. The theory behind this principle is that at idle, soot builds in the pre-chambers which will eventually evolve into carbon that can degrade glow plug and injector performance, not to mention less efficient operation.

It is not necessary to allow your naturally aspirated 240D to "cool down". MB turbodiesels benefit from 60-90 seconds of cool down due to the extremely hot operating temperature of the turbo. The cool down period allows oil to cool the internal bearings in the turbo which, if not practiced, could lead to premature life of the turbo.

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

I have worked on and drove diesels since the 70's and I always warm mine up and leave it running when I go into a store. If you can afford the fuel leave it running, those farmers usually know what they are talking about...

__________________
2000 Ford 7.3 Powerstroke 4x4
2006 Mazda Tribute
1983 Black 300 D (donated to charity)
1993 Teal 300 D (160K) Sold
"I love the smell of burnt diesel fuel in the morning, it smells like ....VICTORY"

Semper Fidelis
USMC 1973-1976

Cummins warns against a long idle period. Could be the carbon build up and related oil contamination.

MB emphasizes the detriments that can occur from extended idling beyond 1-2 minutes as well.

Farm equipment is different than an MB diesel of any vintage. Starting in about 1974, MB diesels have had an advanced pre-chamber design which aids in efficient combustion. The soot buildup that can result from extended idling will GREATLY increase engine wear, far more than shutting down and restarting.

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

Okay, but those of you with high mileage engines will understand thispoint
I could not drive my 300SD turbo diesel when cold (-20, 530000 miles), without a 5 minute warm up, it simply had no power. Thus, I always let my diesel warm up a little, turbo or not, cause I do not want another engine like that! It will not climb a hill period untill warm (needle moving up), just not enough compression anymore. I have driven a few cars at the shop I worked at like this as well, something that just happens to old MB diesels.
Have you ever tried to change your oil after 5-15 minutes of driving in a cold climate-it is still thick and will not drain! Even after driving it a little. Scary how thick the oil still is, and how poorly it must circulate during warm up. Give it 2 minutes every cold start and two minutes after a long drive, the owners manual even supports the cool down (every car manufacturer). Have you ever noticed after you restart you car (sitting 10 minutes after a long drive) the temp needle is higher! Cool down helps the engine stay cool once turned off, longer head/head gasket life.
Avoid excessive idling, yes, but give it a chance to circulate oil properly and avoid heat stress in hot climates with cool down.

Of course, what MB recommends assumes that everything is in proper working order. A diesel that has no power starting off, irrespective of mileage, is not in proper working order.

No load = no heat. Therefore, the engine oil will not warm in the crankcase until there is HEAT.

A cool down is VERY important for turbo engines, but not recommended (MB TSB, 2/91) for naturally aspirated diesels. Do NOT be concerned about head gasket problems until the temp. reaches the red zone. There IS a reason the temp. gauges on MB's have actual temperatures! 80-85 degrees C is perfectly safe.

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

Golden Bear, I'm with you about the no load = no heat. Diesel engines burn very little fuel when there is no load so the oil may take forever to warm up.

I also have a VW diesel that proves that. When it's very cold out and with the engine warmed-up then idling for 10 minutes or so, I can drop the temperature gauge below the lowest mark with only the blower motor running on HI. After resuming driving, the engine heats right up again.

If thick oil is a concern, then definately a winter grade should be used. I read once that synthetics don't coke up as much in the turbo bearing area if you forget the cool down time because of higher smoking temps or something.

123 300D,

Your assumption regarding synthetics is a true statement. The lower pour point DEFINITELY allows the oil to flow more easily on initial startup. Additionally, synthetic oil does assist in cooling the internal bearings in the turbo more quickly, as well as providing better overall protection due to its high flash point.

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

I run 5W mobil 1 in the winter and let my car run when I go into stores too. The dealer can get you another key. (bring your VIN number)
If Mercedes has a problem with idling, my car would have died years ago. Last December was the coldest on record in Michigan, I've had quite a time starting my car, plugged in three different places. I would have run zero weight, if I could.

__________________
When I close my eyes, and inhale, I can smell No. 2.

First, always watch your gauges when starting your diesel. Make sure that the oil pressure comes up and stays up after starting. Also listen for excessive mechanical noise, and especially timing chain noise.

Second, when starting a cold engine, always allow at least two minutes for the car to warm up. Longer if the ambient temperature is extremely low. Shortly after starting, slightly increase the RPM above idle, say 1500 to 2000 RPM. While the car is warming up the crankcase oil, you can check your lights and mirrors, and put on your seatbelt. It's far better to allow the car to circulate some oil than to just drive away and put a load on a completely cold engine. It's also not advisable to shut down a cold engine that has not been allowed to completely warm up.

Third, Leaving your car idling at the curb or in front of a store is bad for the engine, and bad for the environment. It is also illegal in some states. Don't worry about it restarting. The engine will store more heat shut off than it will idling. The only exception to this would be if you just pulled off of the freeway after an extended run, and were just going to run in for a minute. In that case the engine is better off being left idling to serve as a cooling down period.

Finally, You do need to take a couple of minutes to allow the engine to cool down after an extended drive, especialy if you've been driving at highway speed, to allow the oil to flow through the turbo, engine, and the oil cooler. When an engine is shut off, it builds up a great deal of heat.

Also, I highly recommend the use of synthetic motor oil, specifically Redline, or Mobil 1, or better still, if you can find it, Mobil DelVac 1. Another great oil is the Voll Synthese from Lubro Moly (Liqui Moly in Europe). They make a 0 viscosity oil, and one specifically for diesel engines.

http://www.liqui-moly.de

http://www.mobil.com

http://www.redlineoil.com

__________________

Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."

My experience has shown that letting your car idle is a good thing. I never take off in any of my cars without warming them up (gasoline or diesel). The only exception are brand new cars... and I even believe in warming them up too.

On my car, 81 240D, their is an idle adjuster knob that you can turn specifically for warming the car up. It saves gas, time, and does it much smoother than while just letting it idle. Once the needle passes the first mark... I will take off.

As the engine warms up you have to let the idle adjuster down because it appears to rev harder and harder as the engine gets more heat.

But I did not know that long term idleing could hurt your engine... thanks for the information. Where did you read that by the way goldenbear?

On the oil end I started using the Liqui-Moly Diesel oil after a indy parts shop recommended it. It works good. I have stayed away from synthetic oils because I was told unless you have a fairly new engine... the synthetic oil will clean up all of the gunk in the engine... some of which helps seal the engine. As a result it may start to leak. Since my engine already leaks a bit... I don't want to open anymore up.

anyone with a turbo still running a cool down cycle before shutting down?

__________________

I also warm up my car a little before I drive.
Even locked I would be afraid to leave a car running for fear someone would bust a window and go for a "Joy Ride".
When I get home in my drive way I sit in the car and let it run alittle.
While the car is warming or cooling a little when I get back I use it as focus time to listen to my engine.

__________________
84 300D, 82 Volvo 244Gl Diesel

I do at home in my drive way when I remember but I doubt if I even wait for a full 60 seconds.

__________________
84 300D, 82 Volvo 244Gl Diesel