Vaccum leak comming from under dash on drivers side

[tx73vette]

I noticed a air sound comming from under the dash on the drivers side yesterday.. Where could this be comming from? The lights go up and down with the exceptiuon one is slower than the other. Is there other vaccum connections other than the lights? I will take the dash off this weekend. Where should I look?
Is it hard to remove the dash panel? Would this affect the carburator too?



Thanks

Daniel

 

[Bob Chadwick]

The main vacuum line for the lights comes in from the carb, through the firewall and hooks to the headlight switch. From the switch it goes down to the bypass valve on the bottom of the dash pad. From the bypass it goes back out the firewall and to the lights. The linked diagram includes the wiper door relay that was on the earlier Vettes but I think this was gone by your year.

If it is to the lower right of the dash it could be your heater controls which are more complicated.

 

[MMM]

Leak is probably from the headlight vacuum system. See if you can tell if the hiss is toward the top of the dash near the headlight switch or at the bottom. Luckly it will be at the bottom and if so you do not need to remove the dash panel. You can remove the trim piece at the bottom of the steering column and the headlamp override switch mount should literally fall out and repairs can be made without removing the panel. but if it is a broken hose or at the headlight switch, you MAY have to at least pull the dash panel out far enough for access. You will also need to remove the foward piece of the center console to allow movement of the dash panel and other access
The worst situation would be if the leak is in the heating / ac system controls. The door damper controls are harder to reach. I have had luck getting to them without removing the left dash panel, but you need to be small and be able to twist your body into strange positions. I have found it to be easier to leave the dash in place and remove the drivers seat for better access to the underside of the dash.
ANY vacuum leak will affect your carburetor and overall engine performance.
Good luck,
Mike

 

[JENSHAMMER@HOTMAIL.COM]

I had the exact same problem. Turned out the headlights were fine, it was my vacum assisted brake booster. Perhaps someone else here will be able to tell you how to test to ensure the booster isn't leaking.

 

[tx73vette]

Thanks for all the great help... This Forum is the BEST... I will look at it this weekend..

Thanks


Daniel