Topic: AIR check valve
in Forum: C4 Fuel, Emission Control, and Exhaust Systems
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Montgomery, AL - USA
Joined: 4/19/2012
Posts: 47
Vette(s): 1986 Gray/Blue Z-51 Coupe & 1998 Pewter Coupe
Been working with the exhaust system on the 86- and found this potentially expensive to fix condition.
There is a check valve between the exhaust manifold tube and the AIR pump that was stuck open and allowing the raw exhaust to pass through a rubber tube (that was cooked, cracked and leaking) and alowing the exhaust to blow directly into the altenator. An easy fix with readily available parts (Auto Zone). BTW the other side was in the same condition.
A clogged cat converter contributed to this problem.
Fred in Alabama
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i'm surprized about auto zone having the parts to fix your proplem. what kind of cat did you put on. i was thinking of putting on a mag flow cat and mufflers. of corse i'll keep my orginal one's. i have heard of guys just takeing the cat off and putting a pipe in its place. what do you think of this. 
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Montgomery, AL - USA
Joined: 4/19/2012
Posts: 47
Vette(s): 1986 Gray/Blue Z-51 Coupe & 1998 Pewter Coupe
The check valve is a one way valve that comes off of the exhaust manifold and runs to the front of then engine and on the air pump. One end screws onto the tube and the other end is a ruber hose to the air pump.There is one on each side.
The idea is that when the pump runs it will generate enough pressure to open up the valve and pump "fresh air" into the exhaust system to reduce emmissions.
What happened is that one cat converter was clogged up and increased the back pressure to the point that it blew back through the check valve and backwards into the air pump. The one on the drivers side destroyed the connecting rubber tube and blew hot exhaust into the back of the altenator- fortunately I caught it in time before it fried the altenator- heard the increased exhaust noise and noticed the additional heat in the car.
These check valves were in stock but did not include the connecting hose which I bought seperately.
There are three cat convertors (one main and two secondary) and I know of some that have removed some or all of the cat convertors and had no problems such as check engine lights. This may not be the case for all C4s.
Hope this helps- Fred
in Forum: C4 Fuel, Emission Control, and Exhaust Systems
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