vacuum experts please
Thread Starter
Drifting
Joined: Feb 2001
Posts: 1,539
Likes: 63
From: new ulm mn
vacuum experts please
Two years ago, got my '69 back from an oil change and noticed that I had a vacuum leak somewhere in the car, sounds like from under the dash. No leak before I had the car serviced. Did not bring it back because of inconvenience and probably would have ended up costing me. Fast forward to today, I am finally going to tackle this vacuum leak. The wiper door works and so do the headlights. When the car is shut off, the passenger headlight comes back up. Here's the key, when I am in the car and turn on the headlights, the vacuum hiss goes away. Shut off the headlights and it is back. Open the headlights with the bypass valve, and hiss is still there. Any ideas? Stuck my head under the dash and can't find any obvious loose hose. Thanks in advance.
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
With the headlight switch in the off position vacuum through the headlight switch is open. When you pull the switch it blocks vacuum at the switch which directs the relay valve to open the headlight doors. Since you hear a vacuum hiss only with the switch off and not in the on position my guess is that you have one of 3 possibilities.
1. a leak in the headlight switch.
2. the rear vacuum line has come off the headlight switch.
3. the vacuum line connector has come off the headlight door override switch below the steering column or the override switch itself is broken and leaking.
With the symptoms you describe it should be one of those three. Check the vacuum connector at the override switch first as it is easiest.
1. a leak in the headlight switch.
2. the rear vacuum line has come off the headlight switch.
3. the vacuum line connector has come off the headlight door override switch below the steering column or the override switch itself is broken and leaking.
With the symptoms you describe it should be one of those three. Check the vacuum connector at the override switch first as it is easiest.
Last edited by CanadaGrant; Mar 28, 2017 at 12:58 AM.
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
in for service, my bet is someone unfamiliar with corvette small foot area, with big feet kicked the vacuum lines, might have even cracked 1 of the vacuum push valves, they are made of plastic.
Racer
Joined: Apr 2008
Posts: 406
Likes: 46
From: Lebanon OH
The headlights on my 79 would bump up when I shut the car off. Turned out to be a bad check valve coming off the manifold. It's easy to check and may solve a problem that seems related to your leak but isn't. Good luck.
MajD
MajD
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
Not sure this is where your vacuum leak noise is coming from, but its certainly why your headlight door is popping open.
