Engine/Transmission (1998.5 - 2002) Turbo coking from lack of cool down?

[Pit Bull]

Anyone have this problem? What oil were you using when this happened?

 

[HeberRam]

Pit... . I think turbo cooking because of tooooooo much boost!





Steve

 

[illflem]

Pit, coking the turbo is a long term type of thing with no at the moment symptoms, doubt if most folks realize it when they do it.

 

[TowPro]

Your turbo has engine oil passing through its bearings located between the intake and exhaust side of the turbo.



This oil not only lubes the bearings, but it cools them. You figure that turbo gets pretty hot with all that exhaust passing through it.



Now when your going down the road, that turbo can be spinning around 20K RPM. Now pull into a parking lot and quick shut off the truck, and that turbo is still spinning. I have heard people say it may still be spinning for a minute after shutdown.



Now that you have shut off your truck, the oil supply to the turbo stops. Even if the turbo was not spinning, its still real hot in there. Now that the oil flow has stopped, the bearings will heat up to match the temp of the rest of the turbo, which may be hot enough to burn any oil left in the turbo. when this oil burns it leaves a hard coating of burnt stuff on the bearings and shaft. This is called Coking.



There are several ways to prevent this.



1-Let the truck idle before shutting it down. This allowes the turbo to cool down, as well as slow down. With an EGT gauge mounted Pre turbo, I used to wait until I saw 300 deg before shutting down. An EGT mounted Post turbo is better for seeing what the real temp of your turbo is.



2-Buy one of those Turbo Savers which allows the truck to run for a preset amount of time after you take the key out. Kind of tough to do on a manual trans if you like to park it in gear.



3-I have heard of these oil acumulators that will continue to feed oil into the turbo after shutdown.



4-Run synethic oil, as it needs to get hotter before it can burn.



In my 2002 I will use number 1. I just let it idle for around 30 seconds (or longer if I was just moving a load or running hard) before I shut down the engine.



Its just one of those things that make driving a diesel different then driving a gasser. Like waiting for the "wait to start" light to go out when starting, instead its a "wait to shutdown" before getting out.



Sorry I really don't think I answered your direct question. I don't know of anybody that had the problem in a Ram. I did overhaul a turbo off a grand national engine (before I dropped it into a Chevy Monza) That turbo had all kinds of crap stuck to the shaft. But the owner never changed the oil. I got the engine with 50K miles on it, with a waisted bottom end (crank had 3/4" end play!), and 2 burnt exhaust valves. All caused by abuse and lack of maintaince.

 

[amsoilman]

Good description and advice Towpro. Personally I use synthetic oils in all my vehicles, including a 1988 Dodge shadow/turbo which has 154,000 plus miles. Still runs as good today as it did when new, and never has had a problem with the turbo or injectors.







Wayne

amsoilman

 

[Pit Bull]

Thanks Towpro, good information. I have alway waited at least 1 minute before shut down and up to 3 minutes, if I was on a long drive. Probably over kill. I agree Amsoilman that for me this would be a good application for synthetic oil. In about 20K miles Got to break her in first.



I would assume that the turbo gets hotter based on the load. Meaning if you are close to max-GCWR and you are pulling down the road at 70 mph, you need to let it cool down for 3-5 minutes before you shut the engine down ??



I would also guess that these turbo's must not coke up very easily or we would hear about a problem on the TDR??



Thanks for the responses.

 

[jerryrigg]

Towpro said it all. . just about... one other thing you can/should do is drive like a little old lady for the last 1/2 mile to a mile (when you can) in other words stay out of the pedal/turbo... this can be hard but doing this will drop your EGT to around 400 by the time you park so your wait to shutdown is shorter



-Matt

 

[LSMITH]

I think this is another one of those subjects that we get WAY too anal about. The guys that have never heard of the TDR and don't know that they HAVE to cool the turbo are not replacing turbos at an interval that is even remotely scary. They just shut it off, maybe 400* or a little more sometimes. We run a bone stock turbo to 40 PSI overspeeding the crap out of it for the balance that is on it, and feed it 1500*+ exhuast. Hmmmm, wonder which is worse?



Under 400* I really think you are going to have to shut it down that hot for well over 100K miles to even have a chance of seeing a problem with the turbo, probably never see a problem. The exhuast manifold will crack on you in a hurry, but don't worry about the turbo.

 

[illflem]

What I've always heard is more of a problem than turbo bearing damage from inadequate cool down is that the coke that forms gets flushed into your oil the next time you run it. Sort of like adding sand to your oil...

 

[Excessive Force]

OIL ACCUMULATOR

A few years ago i had a turbo fail on an OLIVER tractor,and i bought an oil accumulator from SUMMIT racing. It was made by BODA,and it has a check valve that releases the accumulated oil to the turbo when the oil pressure drops (shut down). It seems to work great. It was made for turbocharged autos,and i don't know if they still offer them.

 

[MLee]

turbos are tough

when i was working, the guys would abuse the engines in the trucks we drove, (all diesels). run the heck out of them, no cool down, shut them down rite after a hard run. start them up on cold days and mash the throttle to the floor. i expected the engines to fly apart. in 33 yrs i seen only ONE TURBO replaced. these were in-line 6 navastar IH engines and a few fords with 6 cyl. the company ran 15/40 oil year round and changed it every 90 days. the amount of REPAIR that was done, minimal. so the i-6 is one tough bird, no matter who builds it.



Marv.