Hissing noise after plenum pull

[1991KOTH]

The car makes an odd noise when its cranking, then when it finally starts it idles up to 3000 then comes down. Hissing appears to be coming from front drivers side near the throttle body.

Also: The car is not taking anymore coolant after draining it. Ive tried jacking the car up on its side to burp the system, but only a few bubbles come out. Any help?


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[Young1]

I can help you. I live in Ocala. I will pm you my phone number.

[Jim Stanley]

My 90 ZR1 has a whistle when idling warm. My plenum was also recently R&R.
I would be interested to know what you find. Thanks!

[Jagdpanzer]

Hissing usually is a leaking plenum gasket. First try re torquing according to FSM procedure. If that doesn't solve it then try Jerry's thicker plenum gaskets which is what I did.

[Jim Stanley]

Thanks, I'll check it out!

[1991KOTH]

Originally Posted by Jagdpanzer

Hissing usually is a leaking plenum gasket. First try re torquing according to FSM procedure. If that doesn't solve it then try Jerry's thicker plenum gaskets which is what I did.

Turned out to be a loose hose feeding into the plenum


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[Jim Stanley]

Thanks for that info.

Back in the day I would use a propane torch (unlit of course) to look for vacuum leaks. When the propane gets sucked in the rpm goes up a bit.
Has anyone found this to work on the ZR-1?