1969 vacuum trouble.

[Forrest J.]

I am having a vacuum problem on my 69 Corvette that I can't solve. The wiper door opens when the vacuum bleeds off on the car. It is usually down to about 3-4 inch pounds when this happens. The system holds vacuum over 30 minutes. I have replaced all the hoses (Dr. Rebuild) and the check valve is good that feeds the storage canister from the intake. I have changed and adjusted the valve at the right side of the car at wiper arm. I realize it's kind of a race for the service side to bleed off enough so that when the signal side (small white) runs out of vacuum there is not enough vacuum left to operate the wiper canister. The headlamps don't try to open upon bleed down although they would require a lot more vacuum. I have had all the canisters,headlamp relay and wiper relay rebuilt also. The by pass valves inside the car seem to be good. Maybe something easy I am overlooking. Any ideas? Thanks. F.J.

[Bill C.]

Re: 1969 vacuum trouble.

any chance the manual vacuum override switch under the column is not closing completely?

It is the only other item I know that can send a signal or lack of one out to the relay valve under the hood.

my best guess.

[Forrest J.]

Re: 1969 vacuum trouble.

I believe it goes straight through there o.k. I will check again. All the cars bleed down at some point so I am missing something. Thanks. F.J.

[Gary H.]

Re: 1969 vacuum trouble.

Replace the switch on the wiper. Find an original gm switch. The replacement switches are awful. My car did the same thing 2 years ago 3 days before going for a PV. I replaced the switch with Ecklers garbage because of the timing, even called and paid for fedex overnight and the next morning it happened again. I found a real gm switch and problem solved.

[Forrest J.]

Re: 1969 vacuum trouble.

Gary, I will try to find one. I just put one on from Paragon so who knows. Most of the Corvette after market comes from the same vendors I think. Thanks. F.J.

[Alan S.]

[Forrest J.]

Re: 1969 vacuum trouble.

Hi Alan, I have looked through old post and am not sure about seeing the post you described. I will dig around and try to find it. You are right about the design. It is quite a system. I have looked and tried to figure exactly how the bleed down and timing of it works also. An engineers dream. Thanks.

[Forrest J.]

Re: 1969 vacuum trouble.

Hi again Alan, I did find the write ups from Jack Humphrey and will study them in detail. Thanks again. F.J.

[Alan S.]

Re: 1969 vacuum trouble.

Hi Forrest,
Good! I hope you find something that helps you.
Jack really has written some good things!
The 71 has a one year only Combined Emission Control system that Jack spent a LOT of time and effort on, and then wrote an article for the RESTORER about the system. It's a God send for 71 owners.
Good Luck!
Regards,
Alan