Cooling down a turbocharger.

How long do you idle a diesel engine to cool down a turbocharger? I understand it has something to do with "coking" the oil in the bearings if shut off while too hot. A neighbor lets his run for five minutes. Newer engine design has the turbo oil fed straight out of the engine oil cooler to help with this.

Please let me your thoughts on this.

Thank's again

Beagle

Another good reason to have a pyrometer installed if you don't have one. When the exhaust temp is below four hundred degrees it's safe to shut down the engine.

I don't see that it is that big a deal. The main problem is when a turbo is in boost and is suddenly shut down. Caterpillar, in the manual that came with my truck, was apparently not very concerned. I believe that it is because it is so rare for a truck to get shut off when in boost. The scenario nearly all the time with any machine is that it gets throttled down and run at lower RPMs and light load until it gets to its parking place. Two major examples where you need to be concerned is a tractor under PTO load or when one stalls under drawbar load. I was working on a tractor that I bought used, and had the intake pipe off the turbo. I noticed that the wheel did not spin freely. I removed the oil pipes and sprayed WD-40 into the oil inlet until it came out clear, and it freed up. Another tractor came with a sticker on the inside of a window that said to cool it for five minutes if it was to be shut down after being under load.

I let all my motors (from trucks to cars to tractors to mowers gas or diesel) cool down before shutting them off. By cool down, I mean allowing them to idle or low rpms for a minute or so before shutting them down. If I'm in a field, I may idle the tractor down and drive to where I'm parking it and by that time, it's cooled down from it's hard run. For my vehicles, just going down the driveway to it's parking spot is usually long enough to get the EGTs down. I personally feel that a cool down, especially after a hard load, is important for all parts of the motor not just the turbocharger.

The decal in both my Whites says 3 minutes.

A few minutes is probably a good idea, it depends what you have been doing with it, if it's been idling around the yard it's probably not necessary. The owner's manual for our JD 4600 says if you kill it while working it hard to restart it immediately and let it cool down, and it doesn't even have a turbo! I remember hearing about the old start on gas diesels, like a the TD9 that my father had in the 40's, that a hot shutdown could crack heads or warp valves.

Some operator’s have a bad habit of blipping the throttle prior to shut down.

Always a good idea to let any engine idle for a few minutes before shut down. From what I have read this particularly true for air cooled engines. I have an 06 Dodge Cummins that has a programmer that includes an EGT reading. This programmer will let the engine run after you turn off the ignition if the turbo temperature is above set limits. After I have been pulling hard the engine will idle for about a minute till the temperature drops. You can see a 500 to 700 degree drop temperature in that time. It?s not often that you go from running full blast to nothing. Just pulling off the highway and idling to a parking place is usually enough.

OTJ

Not only does it allow it to cool down but slow down and it allows the cooling system to pull heat out of the head. When you run up stop and shut down that turbo is wizzing , not as hard as when under load and it is spinning on a film of oil . Remove the oil pressure to soon and the bears will take hit . Maybe it will not affect them all at once but over time they will ware and then the seals start to go due to sloppy bearings . also when you just shut down combustion chamber temps rise and the coolant flow is not there to pull the excess heat out . My one friend is on his SECOND turbo on his Dodge because he thinks it is like a gas engine . Fire it up allow no warm up and out the lane and down the road full tilt , get to where your going pull in and shut down as your walking away from the truck you can hear the turbo spooling down . Years back while working in the oil patch i ran a 750 Deere dozer and a 450 C ,Both had what i thought was a extream high engine idle , the 450 was up around 950 and the 750 was over a 1000 RPM . Even letting them set and cool down for 10-15 min while you cleaned tracks when you shut them down you could still hear the turbo spinning for 15- 20 seconds after the engine was shut down thru the mufflers.

a few turbo engines have a extra oil tank for the turbocharger, racers had them as 'spin out bottles'. a Ford engine had a extra FL1 oil filter just above turbine shaft with small bypass valve- shut off engine, no oil pressure and bypass would open enough for large oil filter contents to trickle into spinning turbine bearing housing to save bearings. restart engine and some of oil would go through bypass for a minute, then through the filter that would be refilled. Same setup as after market install for some IHC engines as used on a few tractors, available for some other installations depending on space available, originally a aircraft engine option. idle down couple minutes preferred but the extra oil bottles did save many abused turbochargers. RN

Use a good quality synthetic oil and it won't coke. You can do your own test. Get a frying pan hot enough to burn cooking oil. Then try a little conventional engine oil of your choice at that temp. It'll burn and stick. Good synthetic oil may smoke a little but won't coke. I'd never run a turbo without it.

Yes it is a good idea to let any engine cool a bit,, when you shut them down hot they actually build heat for a bit because the cooling process has stopped abruptly..3-5 minutes or so will help depends on how hard they were working at the time..

Had a '79 International 4070B with a 3408 Cat that had a tag on the console from the factory that said idle for 5 minutes to cool the turbo down. Right, wrong, or indifferent as a practice I've used that as the bible ever since. Times and technologies have changed and gotten better I'm sure, but 5 minutes as a minimum works for me. Engine oil under pressure plummbed through the turbo has been around about as long and was a great and simple idea to insure turbo lube.

Good luck.

Mark

Saw it happen where a turbo was trashed from hot shut down. A combine would lose oil pressure so operator would immediately shut it down. Check it out, restart, would run fine and later, same thing. Don't know how many times this happened but the turbo started throwing oil out exhaust after a few times of this. Found out it only happened when on a slight side hill and oil pan baffle had come loose and would suck up on oil pump pickup tube.

I had a neighbor who thought the slow warmup, slow cool down was overrated and a bunch of bunk. At the end of the day he would pull out of the ground, Park the tractor at the edge of the field and shut it down hot. Next morning if it was cold he would start it up, put it in gear while it was still smoking and sputtering from the cold and put it right to work throttle wide open. He didn’t have any more engine related problems than anybody else, but I would be the very LAST person to buy his used tractors.

When I first went into tanks we were taught a 5 minute cool down at 1000 RPMs. Start up was after the gauge showed oil pressure 1000-1500 RPMs for 10 minutes on cold start. Reason stated was the turbo. We were told that it took a little time for oil to actually get to the turbo on start up. Didn't want to spin the turbo up with no oil. On shut down pretty much the same thing. Let it spool down. When they started selling turbo cars a lot of owners had turbos go out. They never had any training on how to drive a turbo equipped engine. In the late 70's we got new turbos for the tanks. They had a galley built into them that held enough oil so that we no longer had the warm up and cool down times. They also had ceramic bearings. I know a lot of people with modern turbo equipped vehicles and you don't hear about nearly as many turbo problems today. On an older tractor I would err on the side of caution.

Rick