High pitch whistle when warmed up.

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Re: High pitch whistle when warmed up.

Postby Mafix » Wed May 12, 2010 1:29 pm

good times! luckily for me i don't have 90% of the crap on my car you guys do.
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Re: High pitch whistle when warmed up.

Postby 5thgenbliss » Wed May 12, 2010 5:57 pm

you know what it is?.... its Bullsh*t that's what :lol:

I washed her yesterday which made me forget about it for about 10min. :P
Boosting with the '92 GT4 RC
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Re: High pitch whistle when warmed up.

Postby imperfect2099 » Wed Aug 03, 2011 4:20 am

i had this same issue. i had a MBC and i removed it because i had no need for it and the whistle went away. it wasnt the intended outcome, but i was glad it fixed the problem anyways. good luck resolving ur issue.
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Re: High pitch whistle when warmed up.

Postby underscore » Wed Aug 03, 2011 1:24 pm

I've got this too (only when fully warmed up), and I'm told I have a small vacuum leak around that piece that bolts to the TB and goes to the intercooler. I'm guessing once the rubber/metal heats up, expansion reveals the leak, and it's such a shape that it whistles?
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: High pitch whistle when warmed up.

Postby bajachris88 » Sun Nov 20, 2016 11:09 am

This reply is for the purpose of archiving my findings for future reference; it may help others.
(I found this thread via google when i was having the same issue, however it didn't have any findings of resolution for me to follow; so want to share mine for future GT4-ers).

I had high pitch whistle, originally was only when warmed up, then sometimes at 'any time' after 6 months later, however always more prominent when warmed up. Noise seemed to come from under the throttle body.

My MOTEC dash allowed me to monitor intake manifold pressure full time. The difference between manifold pressure when the Idle Speed Controller was open and closed must have been enough of a difference to trigger the noise and was from memory approx 2.5 to 3 psi vacuum.

So... I pulled apart the throttle body, reassembled, cleaned out ISC, put back together, no luck. However, did clean out a bit of carbon.

Used top end engine cleaner to address any further gunk. again, no luck in fixing the noise.

I then said... THATS BLOODY IT! Bought a VRS set off ebay and injector seals kit from a local supplier. I then set forth... (might as well have done a full head job with the amount of work).

On disassembly of the TVIS, I removed the TVIS butterflies and shafts. Only when I removed the shafts, I noted that there was a 'chip' out of one of the two little round 'oil seal style' seals that seals the two separate butterfly shafts as it passes through the intake runners. The position of these seals are central under the throttle body and out of sight for a clear 'spray of aerosol' trial for looking for vacuum leaks. I believe THIS ladies and gentlemen is the cause of our high pitch pain. The revs don't go up, as the vacuum leak is only on ONE of the four intake runners and small (or two if unlucky to have both bad) and too far down the manifold to rev up the other 3 cylinders as it is really at the cylinder head.

Fix: replace the seal after disassembly of the TVIS. unfortunately my TVIS was incomplete and not operational due to aftermarket computer. So i gutted it, and used epoxy metal putty (like JB Weld) to plug up these seal seats. Now all good.

Note: I did the intake manifold gaskets, and replaced the fuel injector O-rings which had their isolators 'pinched' by the numpties that fitted it, however I couldn't find any reason for those to make a 'high pitch' non-rev changing seal that wasn't sensative to spraying aerosol. I'm very confident it was the TVIS butterfly shaft seal.

I hope that helps guys... Basically means a big job but roll up the sleeves and expect alot of cuts on your hands. Removing the tie rod from the wheel hub, as well as the under engine cross member will give you alot of access without a hoist. You may be required to sit in the engine bay with your arm deep under / over (like I did).

I hope that helps somebody.

Thanks,
Chris.
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Re: High pitch whistle when warmed up.

Postby underscore » Mon Nov 21, 2016 6:36 am

I never even thought of there being seals in there, are they replaceable?
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: High pitch whistle when warmed up.

Postby bajachris88 » Mon Nov 21, 2016 8:04 am

With the butterflies and shafts out, the seals just 'pop' out with a bit of leverage; not much force required.

The VRS set didn't include those TVIS seals. I did some basic searching but the auto parts stores referred me to go to a bearing specialist. (CBC Bearings Australia specifically). They would be some 'universal' style seal surely, but by the time I hunted down a vacuum canister and rpm sensitive relay I wasn't keen to wait / pay thus gutted it and plugged it up.
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Re: High pitch whistle when warmed up.

Postby mx6er2587 » Mon Nov 21, 2016 1:45 pm

great info! Not sure I would ever have thought to check that. I removed the butterflies and plugged those ports ages ago on my original trac, but a leak at those seals could explain a noise I can't seem to locate on the new trac.
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