Tracing Headlight Vacuum leak...

Headlights go up but wont go down on own- How do I go about tracing the vacuum leak on this? Car is a '72

Thanks!
Patrick

mrhtwls@yahoo.com

|UPDATED|12/1/2003 12:21:49 PM (AZT)|/UPDATED|

you need a Vacuum guage to begin, then you take a reading at the manifold. Whatever your reading is it should not drop 2 numbers (cant remember the measurement for vacuum initials) under that reading as you check the connections.

First isolate either the wiper section or the headlights depending on which one you plan to work on. Just follow the hoses and you will see. Block off whichever system you are not checking.

Use the guage and follow the hoses checking each connection for vacuum with the guage, once the number drops you know the leak is upstream of that point.

Try to locate a diagram of the system so you can understand the way it flows. There is a great booklet called "troubleshooting your headlights for ..."

I got one from Mid America designs (madvet.com) it helped greatly and was pretty cheap.

Good luck!

See if this drawing helps....

I have a vacuum pump that I use for A/C work. I hook it to the hose at the manifold and turn the pump on...then check for vacuum leaks in all the systems without the engine running. It's much easier to hear a vacuum leak without the engine noise....

Thanks a bunch! I'll let you knwo how it turns out!

mrhtwls said: Headlights go up but wont go down on own-

Patrick -

I had the same problem on my 76. Initially the lights wouldn't even come up. Replacing all the hoses helped that - they would EVERY so slowly rise up. But they wouldn't go down on their own.

Turns out it was the Relay's had gone bad. Replaced those and now they work perfectly and VERY fast once again!

This brings up another question. Do the 77s have one or two relays? Mine only has one and a blocked off hose which leads me to believe there should be two. My lights work, but they're getting temperamental.

besides checking the hoses check the accuator boot and shaft seal. My hoses were fine but the boot was cracked letting air leak out.

mark v