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  #1  
Old 07-02-2004, 01:13 AM
Coming back from burnout
 
Join Date: Jun 1999
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Does a Diesel Turbo ever really Die?

A couple of professionla mechanics have told me that on thr W123 Turbo Diesels, its extremely rare to find a Dead Turbo. I dont know why a Diesel Turbo is different from say a Turbo on a Volvo 940 Gas engine which seems to die at 200K...

If this Turbo Diesel adage is true for the W123's , then does it hold for all Mercedes Turbo diesels in general, in my case a W124 which I just bought and which has no boost (Yet)? Does that extend to Cummin Diesels and even Diesel Genaerators?

The reason I mention this is I remember from working on Merchant Marine Diesel generator governers that the Turbochargers were also very very reliable.

I am not sure if this is to sturdy Diesel Construction or some temperature aspect of the Diesel Thermodynamic Cycle...Finally does anyone ever remeber a Carnot Engine from Thermodynamics??
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Old 07-02-2004, 01:16 AM
Coming back from burnout
 
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To clarify---

is it usually the controls that are the real culprit? Does the turbocharger remain viable while the controls and sensors on them usually fail?
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Old 07-02-2004, 01:45 AM
123c
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I know this has been discussed before, on several threads before, it is sort of the same reason why the exhaust systems seem to last forever... On another note, it also depends on how well the turbo was designed, and if the engine was designed to go with the turbo, also just plain changing the oil every 3,000 miles extends the life of the turbo...
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  #4  
Old 07-02-2004, 01:48 AM
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Turbochargers on diesels tend to last longer because diesel exhaust is cooler than gasoline exhaust. I doubt that your turbo is not boosting at all, but it's more likely that the fitting at the intake manifold is clogged. It's the 12mm nut with a hose barb coming off, in front of the large 20-something mm nut with a single small electrical plug on it.

Measure boost at this fitting (pre overboost sensor) and also after the overboost sensor. It should be 12-14 psi at both ends.
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  #5  
Old 07-02-2004, 04:55 AM
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Location: Pacifica (SF Bay Area), CA
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As mentioned, a diesel turbo should last indefinitely...and the best ways to keep the longevity are to keep the oil clean and to NOT shut the engine down immediately after a long hard run...let it idle for a couple of minutes for the turbo to cool down. Shutting down without letting the turbo cool will eventually kill the bearings, because oil left up there on engine shut-down can actually cook onto the metal...

Actually, I think that most g@$ turbos die because people don't know this.

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Old 07-02-2004, 08:49 AM
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as speedy mentioned, a diesel turbo can last a long time because the exhaust is cooler (because the combustion products undergo a greater expansion than a gasser) and extract a greater percentage of useable power from its fuel. A turbo on a diesel increases the theoretical (or "Carnot") efficiency
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Old 07-02-2004, 11:15 AM
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Benötigt Mehr Druck!
 
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I only can think of one diesel car that the turbo doesn't last. In the newer VW Jettas if you don't excercise the turbo enough the variable vanes get stuck, also seems like they have a bad habit of injecting catastrophic amounts of oil into the motor when the center bearing fails. This oil in the zero clearance motor causes the connecting rods to bend.

Most gasser turbos do fail from coking which is caused by not letting it cool down. Up until last year my turbo with 100k miles (first 3k on dino oil) on it was as tight as the day it came off the line but some how the center bearing stopped accepting oil. (there is NO coking in my turbo either, all I can figure was the opening rusted close in the time it set?!?) I got it back home before it failed but now it feels loose like any other gas turbo with that mileage. My rule of thumb for shutting the car down is to wait for my EGTs to go below 1000*F which may be almost instant if I coasted (cuts all fuel during coasting) a while or it may take a couple minutes if I just stopped boosting.
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Old 07-02-2004, 01:17 PM
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All things being equil a turbo will have about 1/3 the life span the diesel engine does. But nothing is never equal in life is it? Bad fuel and improper fuel delivery upkeep causes more diesel failure's then turbo's. In over the road trucking, turbo's are lasting about as long as engines now thanks to modern oils and proper maintance.

It is common to see the A4 Jetta, Golf, and New Beetle TDI diesels hitting 200,000 miles with no turbo problems as long as the Variable Vane turbo is excerised regulary to keep the little acuating rod from rusting were it will not open fully. The rusted rod however causes no turbo failure and can easily be fixed. What has cause a lot of failures is some improper mfg turbo's. The seals were either bad or improper installed, or died early because of non synthetic oil use.

On the VW TDI's they seldom ever have EGT over 900* F, unless they have been modified or are being run real hard in the mountains or pulling heavy trailer's, then you see EGT in 1100* to 1150* range. But for short periods that's not a problem as long as a FULL senthetic diesel rated oil (soot control) is used. The same should be true for the 123 turbo's even though they have a wastegate system (VW went back to wastegate on the 04 models) and if you want to really reduce the EGT on the car then reduce the back pressure on the exhust system.
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