Ok, this is long, but hear me out.
Last fall, when I was hauling my truck camper around I started hearing what I thought was my turbo screeching, but it would only do it after a sustained load @ 65mph in 3rd T/Q locked.
I checked over everything I could think of, & couldn't find anything wrong. After offloading the camper, I couldn't get it to do it again, so I kind of ignored it.
Well, after loading my camper up again, it did it again, & this time I did some experimenting.
It only does it in 3rd T/Q locked above 60mph, with 20# + boost. It starts gradually with a normal screaming turbo sound, but will transform into a metalic screach after a minute at steady speed. If I hear it starting, & give it more fuel fast, or let off, it won't do it 'till boost/rpm steadys out @ sustained speed.
It sometimes will quit when I hit a big wind gust, @ won't do it at all in O/D enless it's doing it before it shifts.
The only thing I can think of is an air turbulence getting to the compresser wheel. I don't remember it doing this the year before, when I had the rubber shield in front of the air cleaner. I removed it last year before the trip. I have now put it back in, & will test it again when I go out next time.
Anyone got any other ideas?

 

Almost 100 looks, & no one has a clue?

 

Make sure you pull the intake off of the turbo. If it is touching you should see scaring on the wheel or the housing. Mine will make a funny noise when the engine is cold sometimes, but not for long.

Oh yeah, A boost leak will also cause this under heavy load. You need to pressurize the system and check for leaks.

 

BOOST LEAK...................

 

Yup, I am going with the boost leak. Check all the air tube boots for tears and loose clamps.


Tim

 

Well, I checked all my clamps, etc. before. It also won't do it with 32# of boost, & 1250* egt in O/D, but will do it @ 22# boost, & 950* egt in 3rd. So heat soak isn't it. I also personaly dialed the turbo, & also the installer did too, & there is nothing wrong with it. I even looked for signs of an exh. gskt leak, & nothing. I thought it was the fan clutch for a while, but it does it when the temp isn't high enough to engage it. Like I said, it will only do it @ 65+ mph in 3rd with the T/C locked, & some times a big gust of wind will stop it for a moment. And it will wait for sometimes 2-3 miles on a hill before it starts.

 

Does it do it without the camper on the truck?



Tim

 

radiator fan??

 

No. I can't get it to do it without the camper's load on, & even then it won't do it unless it's above 20# boost. And if I gradualy increase speed, & keep building more boost trough the range, it won't do it. Only when I set the throttle for sustained speed on a grade. I also can't find anything wrong with the fan, or fan clutch. I think it started when I removed the rubber shield from in front of the air cleaner last summer. I have now put it back, & will test it in a few weeks when I go out again. All I can figure now is that there may be some turbulence caused by the gap between the radiater, etc. & the headlight under cirtain conditions. I don't know.

 

Well, after re installing the cover over the gap next to the radiater, I went out for a test yesterday. There are only 2 hills around here that will let me try to re create the problem. I tried them both, & couldn't get it to do it. This still may be because the hills weren't steep enough, or long enough, or the cover fixed it. I guess I won't know for sure 'till I cross the mountains again. I sure hope that's it.