Squeeling Noise Under Acceleration - Belts Or Something Else?

[ausdrift]

I've noticed recently that when I come onto boost under moderate acceleration I hear a big screech sound which I assumed to be a belt. I've tightened the PS belt 2 times already as after having a look, that one appeared to be the loosest. Now its no longer the loosest, the ac one is, but to be honest, while that one has the most slack, I wouldn't call any of them "loose". This makes me a little confused as to what's making the noise and how serious it is.

Background info - Engine done 128k, belts in good condition, belts and tensioners/pulleys all replaced 28,000kms ago, air con compressor works, but leaks green dye and is original. Water pump and timing belt changed with belts.

Anyone know what's going on?

[Yonz]

If the AC is off when you accelerate, but it still screeches, it shouldn't be that as it won't have any load to cause slipping.

Other than that you could try loading up the electrical systyem...

Or take a video of it happening

[Sinista32]

Possibly excessive shaft play on the turbo ............. or fan clutch giving up the ghost

Edited March 4, 2015 by Sinista32

[ausdrift]

i did try accelerating today without ac turned on, but it still made noise. if it was ac clutch/unit would having ac off therefore prove its not that causing it?

[jiffo]

When this happens, do you see 2-black lines on the road behind you?

Seriously though, sounds like a turbo to manifold gasket.

They can make some crazy noises and mostly only start to play up once boost builds.

[Sinista32]

i did try accelerating today without ac turned on, but it still made noise. if it was ac clutch/unit would having ac off therefore prove its not that causing it?

No

[ausdrift]

When this happens, do you see 2-black lines on the road behind you?

Seriously though, sounds like a turbo to manifold gasket.

They can make some crazy noises and mostly only start to play up once boost builds.

ha, I wish. Gaskets never occured to me. Have others had this?

[ausdrift]

i did a little test this morning. If i accelerate slowly up to high revs, i cant hear the noise. If i accel hard and get on boost, i hear it. This makes me think it could be a gasket as it doesnt appear to revs related but rather boost/acceleration related. Thoughts?

[Ben C34]

Yrp

[ausdrift]

Now got a quick video I did today

https://www.youtube.com/watch?v=L_ZHS72JW44&feature=youtu.be

Any more ideas, or confirmations? Has this happened to you?

[kingtube69]

I had screeching on boost, it was my exhaust manifold - I had 4 snapped studs!

The video sounds similar to what I have.

While you're working on your car grease your clutch pedal assembly

[ausdrift]

you mean turbo to mani, or engine to mani? yeah clutch pedal needs more than a greese at this point. I think ill need to replace the whole bracket...

[Charles89]

Can't really hear it from the video, but try taking off the turbo heat shield and see if there's any loose studs or any gaskets blown. It will be fairly noticeable.

[ausdrift]

I was planning to get in there and check it out tomorrow. Good to know it should be visible; nothing worse than a noise you cant find. There are enough of those already

[kingtube69]

Mine was engine to manifold I initially thought it was a boost leak but it turned out to be a exhaust leak.

[ausdrift]

Well I spent a few hours ripping the bay apart. I got down to the turbo and manifold. The good was that there was nothing obvious broken or hanging off, which is almost a little bad in that the answer still isn't clear. That said, I did notice that the manifold to turbo gasket wasn't uniform at the edges, and that on both sides there were gaps, suggesting it may be partially disintegrated and boost could be leaking through. As a stop-gap I pushed into the gaps a little high temp liquid gasket to see if I can seal it up a little, just until I work out what I want to do as a proper solution. Also the turbo nut locking tabs had opened out, but I hear they have a tendency to do this over time. I tightened the nuts a little (4th one cant be accessed tho) and put it all back together. Tomorrow I hope to see if there is any change.

[ausdrift]

Test drive today - no change

grrrrrr

[ausdrift]

For anyone reading this Ive done a fair amount of work to the car and its solved it. Specifically I got a turbo high flow and at the same time replaced pretty much all gaskets, studs, nuts etc from the block to the down pipe and the problem is gone. Not really to chase this problem, but it worked out anyway. Not much help in diagnosing it therefore, but looks like it was something there. possibly the dump to downpipe as I wonder how tight it was done up.