Full Boost Squealing Noise - Can't find cause.

[ToNkA]

I have a 1GGTE (standard everything), sitting in an 84 Hilux. (just finished conversion)

All runs well, everything great, but when it comes on to full boost (as indicated by the boost gaugue) there is a deaffinhg squealing noise inside the car.

I thought it was the Boost Gauge leaking air, so disconnected it and could feel air coming out the tube, but on full boost the noise was there again.

I can't work out if the noise is air or electrical, but it certainly is clear and loud when on full boost.

Any ideas?
I can't work this one out and it is driving me insane!

[brett_celicacoupe]

how much boost is it making?

maybe one of the turbos are stuffed

[ToNkA]

Around 9psi, (All stock remember).

It doesnt sound like a bearing noise, and its not like a turbo 'whine' this is really loud inside the cabin...

[brett_celicacoupe]

so it happens in any gear?

youll need to experiment and rule out things in the driveline and intake etc.

[ToNkA]

Any gear, when it comes on to full boost, the noise appears...

I can confidently say it doesnt sound mechanical as such, I really thought it was an air leak at the Boost Guage.

It's like when you let air out of a balloon and you squeeze the end to get the ear piercing noise.

I had the Boost Gauge tube disconected but the noise was still there....

Not sure what tests I can do to locate the source...

[brett_celicacoupe]

is it idleing high? you might have a vacuum leak on the manifold. there is quiet a few tubes hanging out

[ToNkA]

Yeah, it is idling a little high, I thought nothing of it as the engine hasn't really been 'tweaked' since the conversion.

Anything in particular I should be looking for, this engine is still quite new to me.

[brett_celicacoupe]

check all the vacuum hoses sticking out of the plenum. there is a few on the front and a couple on the back for memory.

is the brake booster line connected properly?

[Classique71]

Split intercooler hoses , or a loose clamp on your IC/turbo pipework can cause this too

[EldarO]

sounds like a boost leak to me, ive had everything from squealing to hooting (sounded like an owl, i kid you not)

Elmo.

[Classique71]

mine sounded like an amplified balloon making that farty noise we all giggled at when we were kids - was sourced to be the turbo inlet pipe from the pod filter ..

Once clamed back up - no noise

[ONCE-NA]

I have the same problem after changing all my intake pipes, fitting a plumback bov etc. Havent had a chance to find the source though, it sounds like a kazoo! Or an old guy with a gumleaf...

[JP]

have you got a 1-way valve in the brake booster line?

My chaser did exactly the same thing until I installed a 1-way valve.

[Moppitt]

Ive even seen that kind of noise caused by a warped exhaust manifold allowing exhaust gas to escape between the layers of the metal exhaust gasket, causin them to vibrate and squeal just like you describe. Sounded just like a bad idler pulley, but it only happened when there was some boost (hence there been some reasonable pressure in the exhaust manifold to force the gasses out that gap).

Unfortunately these problems can be really hard to diagnose without seeing (and more importantly hearing) the car.

Everything points towards an air leak though. Good luck with it.

[Negative Boost]

sounds like a boost leak to me, ive had everything from squealing to hooting (sounded like an owl, i kid you not)

Elmo.

I've had this too, well not the owl I've had some pretty bad squealing noises coming from the IC pipes when a join split on me a couple of times.