Sqeaking Noise Behind Dash
 

Good day fellow listers. Recently I started hearing loud sqeaking/screeching noise coming from behind the dash. It only happens when I release the gas pedal to change gear with the AC off. Last night after 3 hours I was able to isolate where the noise is coming from. The noise is actually generated by one of the flaps in the air distribution system of the ACC. This was confirmed when I unplugged the the green vacuum line from the small manifold under the hood on the passenger side.

Question is, is there any difference between the available ports in the manifold ? Last year I moved the green vacuum line from the original port to another free port due to vacuum leak (vacuum pump keeps on recycling). After the switch, the vacuum pump stops recyling itself. Did a couple of test last night. With the vaccum line in the original position, there are no squeaks but the vacuum pump continues to cyle, with the vacuum line in any other free ports, the vacuum pump does not cyle but the squeaking noise came back. Also, with the vacuum line in any port, I can hear a slight hiss coming from behind the dash which is only evident with the glove box and lower dash panel off.

I would appreciate your wisdom and suggestion in resolving this problem. Thanks !

Willy

BTW the car is a 96 W202, stick shift w/ automatic climate control

Any experience, suggestions ? anybody ? Thanks in advance.