I'm still fighting my vacuum drop, which lets my AC actuator / door open or close, whichever; my air flow drops under acceleration then returns under normal cruising conditions. Is there a main vacuum chamber somewhere that may be the culprit. All the vacuum lines look ok, as far as I can tell. I cannot get behind the dash (yet) and the control under the console appears to be functioning properly. I have also had trouble with my headlights not opening easily or at all. Is there a complete vacuum diagram anywhere? I have the complete assy. and Haynes and Chilton for my '82, but they are not good.
On my 78,the main vacuum canister is part of the frame the big cylindrical tube in front of the radiator,I don't know if they stuck with that change from the "coffee can" up to 82 or if they changed back to the coffe can version on yours
Vette(s): black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion
There is a check valve in the headlight vacuum line which goes to the headlight system, check this valve. It is covered at the link that Aaron posted. check the vacuum lines where they connect to the two headlight vacuum relays, hoses tend to loose their elasticity with age and may not seal well there. when checking the vacuum can, check the upper end where water can collect and rust out the seams, mine had lots of small leaks where I couldnt see them. There is a plastic "T" up near the brake booster that sends one line through the firewall to the heater controls, check this "T", mine was cracked just enough to keep my vacuum actuators from working the air control doors. I believe there is a vacuum line which goes to the gasoline vapor recovery (charcoal) canister. All of these lines which leak may add up and steal the vacuum you need to operate other "stuff".
Thanks for the ideas! I've seen all these items and visually checked them and physically somewhat. My check valve leaks back a little ( I did a blowtest ), my filter has been altered to allow stronger vacuum, someone poked a hole through the filter. The hoses all look good but there is probably small leakage everywhere. I wish there was one vacuum diagram for the entire system instead of one for the fuel system, one for the engine, one for the headlights, one for the climate control, etc., maybe we need a forum just for vacuum, it is my biggest headache.
This diagram differs from mine, no wiper doors and there is a cannister up front where the headlights are. I don't know if it is the main tank or where the fuel vacuum tank is? I hope Doc Rebuild can tell me.
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