2nd Gen Non-Engine/Transmission Is my tubo dying?

[TDaub]

I was running from Dallas to Charleston when my turbo quit after about 300 miles on the tank. EGT was about 700, oil temp was in the normal range, outside temp was about 76deg. I stopped and pulled off the intake hose, the blades were spinning. After I stopped fro fuel about 2 hrs later the turbo started working again for about 300 miles, then nothing. till I stopped for the night. haven't had a problem since, but I haven't made a straight run that far since.



Is my turbo dying?



TS Daub

 

[terrywerm]

Haven't personally seen a turbo failure on the 5. 9, but I have seen them on the N14, M11, the old 855's, Mack's, etc. On the older engines turbo failure resulted in LOTS of smoke and no power. On the newer engines, lack of boost would result in defueling, but I tend to think that it would still be pretty smoky, and definitely short on power. Since you have guages, you should also notice a total lack of boost, and high EGTs.



Most turbo failures are one of the following types:

1. Loss of fins - I've seen them go through the turbo housing, and through the piping between the turbo and the intercooler. On the older, non-intercooled engines this usually resulted in a fin (of pieces of such) getting caught in a valve or in the cylinder - not pretty!

2. Bearing failure - often results in the turbine or compressor wheel hitting on the housing, which in turn results in loss of fins. Since the compressor shaft no longer stays in one spot, the third failure can also occur at this same time.

3. Loss of oil seal - LOTS of smoke, no power. Allows turbo to suck oil from turbo bearings and blow it into the engine - this kind of failure has been known to result in a runaway engine, though it's not common. If the oil blown into the engine is in just the right quantities, the engine will run on that motor oil and can start to over rev. Like I said, not common though.



Can you elaborate on why you think your turbo is failing? A more likely problem is a loose or blown induction piping coupling between the turbo and intercooler, or between the intercooler and the intake manifold.

 

[TDaub]

The only thing that I could add is that I had the Cruise Control set to 70mph each time it happened. After the turbo stopped producing boost, I was able to maintain 70 on flat runs but dropped to 60mph on the small hills of I-20 through Mississippi and Georgia. I did not notice any extra smoke. EGT stayed around 700deg.

I did notice that when I was on the down side of a hill (increasing speed back up to 70) I would show about 5lbs of boost on my guage.



Does that help in a diagnosis?

 

[AKAMAC]

Do you have an exguhast brake?

 

[bmoeller]

Haven't personally seen a turbo failure on the 5. 9, but I have seen them on the N14, M11, the old 855's, Mack's, etc. On the older engines turbo failure resulted in LOTS of smoke and no power. On the newer engines, lack of boost would result in defueling, but I tend to think that it would still be pretty smoky, and definitely short on power. Since you have guages, you should also notice a total lack of boost, and high EGTs.



Most turbo failures are one of the following types:

1. Loss of fins - I've seen them go through the turbo housing, and through the piping between the turbo and the intercooler. On the older, non-intercooled engines this usually resulted in a fin (of pieces of such) getting caught in a valve or in the cylinder - not pretty!

2. Bearing failure - often results in the turbine or compressor wheel hitting on the housing, which in turn results in loss of fins. Since the compressor shaft no longer stays in one spot, the third failure can also occur at this same time.

3. Loss of oil seal - LOTS of smoke, no power. Allows turbo to suck oil from turbo bearings and blow it into the engine - this kind of failure has been known to result in a runaway engine, though it's not common. If the oil blown into the engine is in just the right quantities, the engine will run on that motor oil and can start to over rev. Like I said, not common though.

Had a compressor wheel snap in half, on a Cat C-12. Took out the housing, too. :--)

 

[McCRam]

If you try to move the turbo shaft, is there any play? If not and it spins freely, I would look elsewhere for the problem.

 

[PC12Driver]

If the engine wasn't getting the boost needed for the fuel being supplied, you would be getting plenty of black smoke and egt's would be out of control, especially on the 60 mph uphills you described. 5psi while coasting at 70mph sounds about right, too.



Is that 700 degrees pre or post turbo?



Does your boost drop to zero, or does it not increase to where it normally would be?



Any idea what your fuel pressures were when the boost was lost? A plugged fuel filter/bad lift pump would also result in low boost (not enough fuel to provide enough gas expansion to drive the turbo).



A faulty MAP sensor could also limit boost. If the MAP sensor (the computer's boost sensor) doesn't "see" enough pressure, it won't increase fuel delivery to the injectors.



Boost problems due to bad turbos or leaks typically aren't intermittent and don't fix themselves over time. And if you were missing boost you would certainly have a secondary indication of a problem (lotsa smoke and high egts - these engines weren't designed to run without boost). I'd start with the fuel delivery side of things.





BTW, the 24v Engine and Transmission forum may have been a bit more appropriate for this topic...

 

[JoshPeters]

If the EGT's aren't out of whack... . and the truck is still producing power..... I think you have a guage issue.



Josh

 

[TDaub]

Lets see if I can answer all these:



No Exhaust Break.

Turbo blades spin freely, no wobble or binding.

EGT pre-turbo

boost drops to zero



I don't have fuel pressure guage "yet", so I don't know what the pressure was.



Would a faulty map sensor affect the operation of the turbo? I would think that the map sensor was operating fine since I didn't get a lot of smoke during the turbo holiday.

 

[JoshPeters]

If the EGT's are staying normal... . it sounds to me like a bad boost guage. I suppose it could also be a fuel related issue... but you continued under power and it comes and goes... ...



Josh

 

[JCyrbok]

I'm with Josh on this one. Occasionally my SPA boost gauge will act a little screwy and show zero or even negative boost. But boost is still there and normal. A little Dielectric grease on the plugs clears it right up.



Are u basing the "Failure" solely on the Gauage reading of zero? Or is there a loss power, sound different, other wise act different when doing this? Can u hear the turbo spool up when it is doing this?



U would notice pretty significant loss of power, i would think, plus higher than normal EGTs and smoke.



If u want to see if it is failing, try taking off an intercooler boot and drive down the block. That would be the equvilant to the turbo not working. U will notice it!



I would check your quage first, before u start to worring about the Turbo.



Hope this helps. Anyone, if I am off base, let me know.

J-

 

[TDaub]

The only reason I looked at my guages was that I wasn't able to climb those small hills in Louisiana at 70mph, the petal went to the floor and my speed dropped to 60.

 

[JCyrbok]

If it felt like you had a sudden lose of power when it did that, do a search on "dead pedal" there are alot of posts on it and usually means that the injection pump is on the way out. Sorry to give u yet another thing to worry about!.



My truck is in the shop right now getting a new injection pump put in. I had intermintant dead pedal, that started on a trip like u described. Truck would lose power, but rpm and all other gauage were normal, but I could push pedal to floor and there was no change. 30 sec later truck would be back to normal.



ALso check that one of ur intercooler boots is not rubbed through or loose.



Also check ur lift pump, a failing lift pump can cause loss power, so can a clogged fuel filter. Looks like your week end is now full with trouble shooting LOL.



Hope this helps alittle atleast.

J-

 

[TDaub]

Thanks everyone, I have been thinking about upgrading to aftermarket parts I guess I will find out real soon which is the first to go.