I'm stumped with this problem. In the past two years I've gone through 4 rebuilt turbos. Aside from one that failed due to poor workmanship the other three all failed the same way, after about 8,000 km - the locknut on the compressor wheel comes off and toasts the compressor blades. I assume it's got something to do with the back pressure when you close the throttle during shifts or slowing down after the turbo is spooled up. I'm told this is a rare condition. I've checked the following without any indication of problem

1. compression - reading 150, 150, 150 163 peak (several revolutions)vacuum at idle- just under 20 psi & steady
2. by pass valve- opens at 15 in hg and pulses open when you you close the throttle- compared the amount of movement with another and it's identicle
3. waste gate actuator - moves at the required 11 psi
4. actuator hosing - no leaks
5. Electronic boost control - the on/off valve works , and is normally open at idle (dumping wastegate pressure signal to intake)- no idea what the computer is telling it to do during operation
6. Oil pressure is within proper operating range
7. No backfire evident

The turbo rebuilds were done by reputable company(s)- (I switched after the third failure) but now I've got to admit there's something wrong with the engine/turbo - but damned if I can find it.

Oh yeah I've got a stock (except for K&N filter)92 Laser GL (AWD) with about 160K on the engine. My troubles started about 6 months after a head replacement.(the car not mine) but I don't think it's related.

After the latest failure I put a used turbo in running with the wastegate open until I figure it out but as you all know I NEED the turbo boost. I also installed a blow off set at 12 psi as I'm leaning toward back pressure fixes yesterday.

Any ideas would be appreciated as I'm reaching the end my rope not to mention $ I'm willing to shell out.

Thanks

Marty

Have you pressure tested the ENTIRE intake system? An intake leak can cause the turbo to over-spin and I can certainly see that shaking the nut loose. Pressurize the whole system and make sure you can hold 20+ psi

Marty,

There have been similar problems with 2nd Gen cars running high boost with the stock BOV. I think Blake's assessment is a good one.

Another thing you might want to check is the setting on your boost controller. Make sure that you're not trying to generate more boost than your BOV is set to.

Just a thought.

Cheers
Glenn

Thanks guys I'll try testing it this weekend and let you know how it turns out

I tried to pressurize the inlet from the turbo outlet to the manifold inlet and found the bypass valve leaked enough so I wasn't able to build up significant pressure - if the valve is bypassed the pressure builds up okay. Tried another older valve I have and same deal. Is this normal as the bypass routes air back to intake- should it have a solid seal?

Update- discovered the 12V Dc crappy tire compressor I was using wouldn't put out enough flow to up the intake pressure significantly- found a bigger compressor and sure enough the intake pressure builds up then slowly bleeds off. However now I'm back to square one - I still haven't found a problem to account for the repeated failures.