Vacuum Reservoir Replacment

fine69 · 10-26-07, 09:35 PM

When I first start my car, the headlights sporadically rise (and close). This condition stabilizes when my idle is normal (usually after warm-up). The vacuum hoses are all new. I recently had my electrical and headlight system tested. I was informed that my vacuum reservoir is leaking.

I was able to find a replacement, and hopefully it will be delivered relatively soon. I understand that I could have used the coffee can style vacuum reservoir used in later year C3s. It appears to be a tedious job replacing this thing... removal of the master cylinder and clutch linkage may be required (?).

For the time being, I bypassed the hoses from the reservoir and connected directly to the check valve and an adjacent hose. It seems to work - I hope this temporary fix doesn't screw anything up.

Any tips from anyone who's done this replacement before?

bmotojoe · 10-26-07, 11:19 PM

Sometimes my 77 does the same thing when I start it up after a period of weeks idle and has done it the 26 years I have owned it. It is caused by the lack of vacuum during startup as the relay valves do tend to change state on there own for a few brief moment. Cars that have higher lift cams tend to have this problem more then stock cams have and I have even seen cars at the track pop the headlights up half way down the ¼ mile as the same thing is happening there, relays change state because of lack of vacuum.
I wouldn’t worry about screwing things up as long as it’s a temporary condition. I have followed many of your posts in my short time here at CAC and from what I see you like to do things right.
Brian

GTR1999 · 10-27-07, 10:15 AM

I removed the vac tank on my early 69. I was pulling everything out anyway so it was the last thing I removed. Not sure if you have PB but the booster may be a problem? My car is manual- I love them too.
How about rigging up a vacuum source to the system then check all the lines to the lights and wipers, maybe the tank is ok?

Vette79 · 10-27-07, 07:56 PM

Ralph, I just did this project along with the wiper fluid tank and pump. No fun but I learned a few things. You can remove the fuel vapor canister from the bottom. There is a splash plate that can be removed to gain access to the canister. Remove the bottom panel moulding and then there are four large screws to remove splash plate. Then there are two screws or rivets that holds the fuel vapor canister bracket to the wheel well that needs to be removed. This is easier then removing the master cylinder and cruise control servo to gain access IMHO.

petes74ttop · 10-27-07, 11:48 PM

Hi, when you turn on the motor you create vacuum in the manifold. That vacuum goes thru a filter than thru a check valve, which has a "T" built into it. One side goes to the tank and the other side of the "T" goes to the relays. If the relay side has a leak the tank side takes charge first and than as the relay side gets vacuum that pulls the lights back down. I would check the "Relay" side first. Pete.

fine69 · 10-28-07, 08:43 AM

Thanks Guys,

The shop checked my vacuum and determined that my tank has a leak. I have manual brakes, so at least I won't have a booster to contend with.

Jeff, I didn't know there was a splash shield - I will check that out. It will be interesting to see if I get much improvement. My cam specs may very well be a contributor to the problem.

Ralph

DarkShark · 10-28-07, 08:57 AM

Quote:

Originally Posted by fine69

....For the time being, I bypassed the hoses from the reservoir and connected directly to the check valve and an adjacent hose. It seems to work - I hope this temporary fix doesn't screw anything up.

Any tips from anyone who's done this replacement before?

I'm thinking of changing the entire system over to this-

http://www.mcspeed.homestead.com/Our_Products.html

It s an electric conversion...

Vette79 · 11-01-07, 01:30 PM

Ralph, I am mistaken. I was thinking Fuel Vapor Canister under the winsheild washer bottle. Sorry. I forgot about the vacumm reservoir up front for the lights.