Snowman

Hello all!

I am having a good bit of success sorting through my vacuum system on my 71 BB vert. I have gotten headlights and wiper doors to open and close, have replaced vacuum check valve which was shot, have all new hoses and have checked diaphrams on the actuators, replacing the wiper door actuator.

I still have a slow leak somewhere in the system. When I start the car, headlights and wiper door come up, after maybe 20-30 seconds, the headlights go down together, then the wiper door and they stay shut unless I want to use them.

My last guess is the vacuum cannister itself. Tried Ecklers, M-A, Jegs, Willcox with no luck except for a Comp Cams reservoir for BB cars not necessarily for a Corvette.

Where can I find one?

Any ideas appreciated.

Thanks in advance.

Doug

A8skyhawk

I would try giving Zip-Products a call... it wasn't listed on their website but I've had good success with them finding things for me. Their number is 1-800-962-9632. I know they have one for an 80-81... hopefully they can find one for a 71. Good luck.

Alan 71

Doug,
My understanding is that when the doors open and then close it's because there is a slow leak on the 'control' side of the system. I believe when you start the engine the relays should receive full vacuum first (small hoses), and tell the doors to stay closed. In your case the actuators are receiving full vacuum first (big hoses), opening, and then closing when the relays finally signal them to close.
Regards,
Alan.

PS: In 1974 the Chevrolet Dealers had the fellow who designed the headlight and wiper systems assasinated.

jim2527

Thats my understanding as well.

'69-'73 vacuum tanks are no longer available. Paragon can braze a 3rd nipple onto the '68 tank or you can add a later '80-'82 tank.

A cracked/leaky tank will only cause the lights to go up an slowly. Because they go up immediately you can eliminate a bad tank as the reason. I'm not saying your tank is good....I'm just saying its the not why everything goes up right away.

71rdster

Search the forum archive for vacuum system trouble shooting articles. It's been discussed here before for sure. Some vendors also have trouble shooting articles on vacuum systems here is a link to Dr Rebuild's http://www.docrebuild.com/dr-r-web/TROUBLE1.HTML
I'll bet JT Pipers can provide a correctly restored 71 vacuum reservoir. Be prepared to give an arm and a leg. Other Vette parts recylers may have less pristine but still functional units for just one arm. Dr. Rebuild sells the 80 - 82 unit as a relacement for the 68-79 tank. It may just be worthwhile to repair yours, if the tank is indeed the source of your problem.

wattac2

Have you actually applied a vacuum at the smaller hose (control circuit) of the check valve? Did it hold the vacuum for a good long time? Next disconnect any one of the control lines (smaller hoses that attach to the top) from the control valves and make sure the hoses are clear and not plugged. If there is an obstruction anywhere it'd slow down the vacuum buildup on the control side and cause your problem.

Just some additional thoughts.

Andy

toddalin

I've got one for sale. $90 +shipping from 92705.

Snowman

Thank you everyone. There is a lot of good stuff in here.

I like the notion about the relays not have vacuum to start. I have all new hoses and the vacuum relays all work but maybe they leak.

Alan I am glad that person was assasinated. Was he stoned first, then his body burned?

Todd, I will get back to you if I do find I need a tank.

Doug