loud screech when in turbo "help"

[83regal455]

hello
i just put a new maf sensor on my car and i noticed the boost changed drastically from where it was before it ran up to about 11 psi now i shoots up to 20 psi, but my question is i took it out last night and it seemed to sound fine , the next day i took it to work i got into the turbo and it sounded like somebody is "torturing a cat" when i got up above 5 psi of boost any ideas what can be causing this thanks 87 stock gn steve

 

[arista5]

did you check your belt? tensioner?

 

[83regal455]

are you saying that the belt may be to loose because about a month ago i did change the alternator on it replaced it with a used one

 

[Outpost]

Hopefully This Is Not Your Problem...

About six months ago our car developed a similar symptom, which appeared very suddenly. When building boost a loud screech was emanating from underhood. As a test, my wife powerbraked the car while I listened underhood (now that's trust!) and I was able to determine that the noise was definitely coming from the turbo. A subsequent inspection of the turbo by John Craig revealed a bent centershaft. The turbine wheel on the inlet side was contacting the housing under boost. Because no evidence of contact with debris on the turbine wheel was visible, Garrett provided a new centershaft under warranty even tho the turbo was several years old and had been heavily modified. They decided a metallurgical defect in the shaft caused the failure. Hopefully your problem is indeed a belt.

 

[G McCall]

I also had a "screech" under boost"; right after I incorrectly disconnected oil cooler lines by plugging them. Loop the lines or remove oil cooler adapter completly. I'm having new wrist pins installed, for lack of oil damage

Hope you don't have this problem. Check the turbo as suggested.

 

[terryk]

Output,

While I think my screech is the drive belt, did Garrett consider the problem a durability issue since it wasn't contacting the housing?

 

[Outpost]

The inlet wheel was contacting the housing. But because there was no evidence that debris or foreign material entered the turbo and caused damage, Garret was forced to assume that something went wrong during the forging process of the centershaft. It took them quite a while to reach this conclusion, and John Craig was very helpful in making them see it this way.

 

[Chuck Leeper]

Screech???

Easy test. Take the belt off and do the brake stall test.. Noise gone? Not the turbo! Noise there? Not the belt/alt/accessories..
Noise there? take the inlet hose off the turbo and look. end play? side play?? NEW TURBO!!

Cunning and treachery!! .. works everytime!!

 

[Tow Man]

Originally posted by 83regal455
hello
i just put a new maf sensor on my car and i noticed the boost changed drastically from where it was before it ran up to about 11 psi now i shoots up to 20 psi, but my question is i took it out last night and it seemed to sound fine , the next day i took it to work i got into the turbo and it sounded like somebody is "torturing a cat" when i got up above 5 psi of boost any ideas what can be causing this thanks 87 stock gn steve

I'm sure you probably checked this, but here it goes.

Make sure that you didn't blow a intercooler hose off. Also check the clamps. This will make a similar noise to what your describing!

Check the simple stuff first. Good luck

 

[83regal455]

yep your right my intercooler hose was leaking air hoses are shot to begin with but i tightened up the clamp and the noise is gone now i got more boost when it was leaking so if i wanted to get more air the correct way how would i do this i do have an adjustable wastegate but it seems like i cant get no more boost by adjusting it... thanks guys and by the way there is no way i would trust my girlfriend with the power brake test (ha ha)

 

[Tow Man]

The adjustable WG is the correct way!

(1) First replace those stock IC hoses.

(2) Check for exhaust leak on drivers side header.

(3) Make sure WG puck has a good seal.

(4) Check intercooler for leaks. Good time for flush and clean if you didn't already!

This should get you started in the right direction.

If your doing 20 PSI on pump gas, keep your eye on knock. The most I can get away with is 18psi on 93 pump premium without knock! I run 3 gals of 114 per tank just to be on the safe side.

Have fun, Vic