talley1968

A while ago I read that a simple vacuum test was to shut the engine down and turn on the headlights. If they opened and closed the system had no leaks. I tried it today and the headlights opened fully but would not close. Does this mean I have a leak? The car seems to run fine - no apparent problems. Could someone else try this and see what their results are. Thanks.

calwldlife

vacuum tank holds an amount of vac that
will be enough to open lights,
if no leaks.
to close depends on amount of reserve and amount of vac needed.

when perfect i could get a half close

i will repeat that a good vac gauge and hand held vac pump is a must when owning a vette with vac systems.

plus the benefit of a gauge to diagnose engine running.

Alan 71

Hi T,
Did you use the headlight switch to test the headlight doors?
You might consider using the headlight door vacuum override switch mounted below the steering column to test the vacuum supply for the headlights.

With the engine shut off there should typically be enough vacuum in the storage tank to open and close the doors at least once.
Pulling the **** down opens the doors and pushing it back up closes them.

The same thing can be done to test the wiper door using the wiper door vacuum override switch.
Regards,
Alan

calwldlife

come to think about it, i could get a firm up/down and 1/2 up.
days after car shut off.

Peterbuilt

Pop the hood and do some investigating.
Cut the ends off a half inch or so of each line to assure a good no leak fit.
Your results are typical for an old Corvette.
If you are into it use this guide to check each part.
http://www.corvette-101.com/vacuum.htm

The heat controls also use vacuum and that is the next area to check.

talley1968

The first time I used the HL switch. Today I tried the O/R switch for both HL and WW. With each trial they opened fully but would not retract. Works perfect with engine running. Car is a 1968 that I've owned since 1970. System is all original except for new HL O/R switch and a rebuild on the WW canister (both done in 1990). Since everything works and engine runs fine I'm not to anxious to start pulling things apart.

Alan 71

Hi t,
If the hoses are all the original hoses you might try clipping about 3/8" off each end of each hose.
There's USUALLY enough length to do this, AND, it gives the hose a NEW sealing surface on the nipple or pipe it slips on to.
MIGHT stop a slow leak down!
Regards,
Alan