Diesel cool down

[OL Creeker]

I found a forum, <www.diesleplaceforum.com>. It it, the "expert" says idling a Diesel engine for more than just a few minutes can be detrimental. When I have to go to the dealership next week to have the Rhino bed liner sprayed in, I'm gonna talk with the service advisor about this. I'll come back with a full report!

[lindy]

The practice of letting a diesel idle to cool down before shut down is and "OLD SCHOOL" practice from when the turbos did not have a waste gate system they have today and the exhaust turned the turbo at full speed all the time, thus the need to let the engine idle down for the turbo to slow down before engine shut down and cutting off the oil supply to the turbo.

[OL Creeker]

I really do feel as though so many of YOU have a lot of knowledge. It's nice that you share it with others! Both DW and I have picked up lots of tid bits.

[Oakman]

When towing with the 6.4 diesel, Ford recommends allowing the engine to idle 3 to 5 minutes to let the turbos cool down.

[ChooChooMan74]

My diesel mechanic strongly recommends to allow the turbo to cool. He advises me 2 minutes for normal driving. I go 2 minutes or 250 on the pyro. This is to prevent the oil from coking in the turbo and having a premature bearing failure. My book even says to allow for cool down.

[joelek]

It is old school and it can still apply to engines today. But only if you have been hauling a heavy load, working the engine, and the turbo is VERY HOT! Shutting it down right away while turbo is hot tends to cook the oil into goo. I would not let it idle, just drive around soft for a few miles at moderate speeds to keep coolant and oil flowing. Then shut it down as normal after the engine and turbo have had a chance too cool back down to normal operating temps. If that isn't practical for your driving area, then an idle cool down works.

[Frank-VA]

Shutting down hot and the oil flow stops will cause the oil to cook on the turbo shaft. The when over time of starting and shutting down causes the turbo shaft and bushing to wear out. The over time the turbo fins start hitting the turbo housing and then it flies apart and it is sucked it the engine. I have seen this happen on heavy equipment engines. Then to repair the engine the Heads will have to be removed and clean the shredded pieces out of the engine. It this is not done it can cause a busted piston.

[kz08h5]

The main reason for not idling a newer diesel is the DPF, or Diesel Particulate Filter. Under normal circumstances if a regeneration is needed it happens when driving down the highway. To do the regeneration the ECM dumps raw fuel into the cylinders during the exhaust stroke so it can burn the particles in the DPF. This process generates higher exhaust temperatures than normal. I know Duramax engines will throw a code if ECM determines the engine is idling it will halt the process. It will sometimes go into a low (no) power mode until you cycle the ignition, then take it out for a proper drive.

Take a look at the exhaust tip of a newer diesel truck, it is larger than the exhaust pipe and is not sealed to it. That is done so air can be drawn in and mixed with the exhaust to cool the exhaust gas down. The manufacturers don't want people or things getting burned by the exhaust gas when a regeneration is taking place. Inside the DPF the temperature is around 650 C or 1200 F. That will leave a mark.

[jrs_diesel]

The DPF can handle a few minutes worth of idling, especially considering the risk of shutting down with a hot turbo.

At work we have two huge Caterpiller engines for propulsion, two medium sized Cats for generators, and a big rig sized Cat for a backup generator. All of them get an idle cool down before shutdown, and EGT must be at 350 or below. Large turbos are very expensive to replace.

Wastegate or not, turbos do need to cool prior to shutdown. I have an EGT guage on my truck, and even unloaded, can take up to a minute to reach 350.

[PapaSmurf]

I do not worry if I am not towing, but if I have been running at 70 MPH for 3 hours towing the camper, when I stop to make the bladder gladder, I leave the engine running and lock the doors. I figure the risk of someone stealing it is less than the risk of ruining the turbo.

[Cowracer]

I'm on the diesel place forum. Lot of knowlege there, but a few misguided guys as well. Dont call anyone an "expert".

The purpose of cooling down a turbo is to make sure any trapped oil in the bearing dont cook. This can be detrimental to turbo life. I have a pre-turbo exhaust gas temp gauge on my Excursion. I will not shut off my engine with EGT's above 350 degrees. Even after the hardest pull, it only takes about a minute for the heat to decay. Usually, the creep thru my subdivision is enough to do it, and I dont have to wait at all.

the one thing you don't Don't DON'T want to do is rev the engine before shutting off the key. That will spool up up your turbo and it will coast down with no oil pressure. A neighbor had his new (to him) dodge for just over a year. Its got less than 60K miles on it and he already replaced the turbo once. He revs the snot outta anything he drives and shut the key off. You can hear his turbo winding down for a good while after he shuts it off.

My Exy has 188K miles on it, on the original turbo. You don't have to go nutso and idle it for 10 minutes every time you shut it off, but a minute of cooldown/spooldown goes a long way.

BTW, Idling a diesel is not harmful to it at all. even for extended times.

Tim

[chevy2500]

Since all of you seem to be mechaniclly superior to me I have a question. Does the Duramax engine need to be tuned up like the gasaline engines and what are some of the signs to look or listen for to let you know there is a problem?

[drc343]

lindy My 7.3 diesel's wastegate does not open until I have 12.5 psi of boost on the system. You still need to only idle a diesel until the hot oil is pumped out of the turbo and it has spun down. Exit ramp and driving into parking is usually enough time for ours to spin down and EGT's cool down enough to shut down. Main thing is to check EGT's before shutdown or it can cook the oil in the turbo.

[chevy2500]

What about a tune up on a Duramax? What should be done or should anything other than serviceing the engine?

[Len & Cheri]

Originally Posted by chevy2500

What about a tune up on a Duramax? What should be done or should anything other than serviceing the engine?

Follow your service manual. No tune up needed if not listed there.

I let my diesel cool down to 400 or less before shutting if off.

[TURBS]

Originally Posted by chevy2500

What about a tune up on a Duramax? What should be done or should anything other than serviceing the engine?

Only "tune up" practice would be to keep a fresh fuel filter on it.

[ChooChooMan74]

Originally Posted by chevy2500

What about a tune up on a Duramax? What should be done or should anything other than serviceing the engine?

Diesels don't need much. Filters. On mine, I clean my MAP and MAF sensors. Don't know if the Duramax have them.

[chevy2500]

Thanks for the information. My service guy usually changes filters when we change oil about every 5K.

[JeffMc]

Rule 1. Always follow your manufacturers recommendation for your particular truck
Rule 2. Verify what you read on forums. I belong to the Ford Truck Enthusiast site and there are a great many experts on there. For every expert there are a few who are....not so much an expert.
Rule 3. See Rule 1.

[coderider]

The manual for your truck is probably the best place to be looking.

The diesel supplement for my 2012 F350 DRW LB states : "to prolong engine life (especially after extended high speed, high ambient temperature, or high GVW/GCW operation, such as heavy loads and/or heavy trailers), it is recommended that a hot engine be idled for 3-5 minutes which will allow the turbocharged engine to cool down."

If you follow what your manuals say you won't run afoul of any warranty issues either.