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I've narrowed down my problem to a AC/Heater vacuum leak in my 91 Camaro. I have the typical "hissing" sound inside the car as soon as i move the controls out of the off position. The problem that i am having is that this leak doesn't allow the heater control valve to open up and heat up the car when it's cold. All other problems have been fixed ( i.e. no coolant leaks, new heater core, new heater control valve, and correct amount of antifreeze in system).
Have any of you here fixed this problem before? I would assume that i could go out and buy regular vacuum hose to replace all of the lines, but some look manufactured rather than just regular hoses. Any advice would be greatly appreciated.
I've narrowed down my problem to a AC/Heater vacuum leak in my 91 Camaro. I have the typical "hissing" sound inside the car as soon as i move the controls out of the off position. The problem that i am having is that this leak doesn't allow the heater control valve to open up and heat up the car when it's cold. All other problems have been fixed ( i.e. no coolant leaks, new heater core, new heater control valve, and correct amount of antifreeze in system).
Have any of you here fixed this problem before? I would assume that i could go out and buy regular vacuum hose to replace all of the lines, but some look manufactured rather than just regular hoses. Any advice would be greatly appreciated.
Thanks,
Scott
If you remove the HVAC control panel you will see a small disc with a bunch of prefabbed vacuum hoses on it. This is the leak. It is made of rubber and dries out after time.
You have 2 options- replace it for about $20 from the dealership or fix it.
To fix it- remove it from the panel- it is held in by a few 7mm screws. There is a small spring clip(s) holding it together. CAREFULLY remove it- the plastic is fragile and can break as well as the clips. Inside is a rubber disc- remove it and put it in brake fluid for about an hour (or longer depending on how long you can be without it). The brake fluid will cause it to swell slightly and seal again.
It is only a temprary repair- it will last for about a year. You are better off replacing it with a new one.
After replacing the rotary valve mentioned above, I figured out that the problem with mine was the harness that plugged into the rotary valve. I tried to coat the harness end with silicone dielectric grease, but it still leaked. Finally, I got some small-diameter silicone tubing that fit over the nipples on the rotary valve and snugged them into the harness end. You have to make sure that the tubes run to the right locations, but it fixed my problem.
Last edited by vette gator; 12-29-2009 at 09:32 AM.
Do you happen to know the GM part number for that vacuum disc assembly?
-Thanks
__________________ 84 Z28, slow but steady progress. 350 with Performer Air Gap manifold, Proform Roller Rockers, L98 Aluminum Heads (10.5:1 Compression), Body/Frame welded supports/connectors, Engine Bay fully wire tucked, engine harness cut down to 4 wires and relocated behind motor, A/C removed (correctly), ready to turn into hard top.
Im dealing with the same repairs this week with my '91. My question is when should the line going to the heater control valve have Vacuum? With the heat on/off or AC on? Mine doesnt have any vacuum with the heat on/off. My AC needs charged again, slight leak, so I cant run it.
I did find that replacing the thermostat while I had coolant drained for the heater core replacement helped with the can running too cool.
