Vacuum leak assistance please

[BlackVic_P71]

I have been having trouble getting the wagon running, last time it ran it had a vacuum leak(as far as I can tell) and is running SUPER lean. I hooked up a smoke machine to it today and I see nothing escaping under the hood, no leaks at any hoses or connections.
I looked inside to see if the vacuum gauge maybe had a leak...then I saw smoke under the dash on the driver's side.
It is right above the brake pedal, I can only se it coming from here, is there any other vacuum source above the pedal or is the booster the only thing there?

[87gtVIC]

Hey Tom

Right above the brake light switch is the cruise dump valve. It has a vacuum line running to it from the cruise servo. I know its function is to dump the vacuum from the servo when brake pedal is applied. Whether it should be leaking under this type of circumstance is something I cannot answer.

Another common source for vacuum leaks is the half moon thing at the base of the steering shaft accompanied by the shift tube.

I dint know if either of those could produce as much smoke as you are seeing there.


You can always try to isolate the booster by pulling its vacuum line and plugging it to rule the booster out. Same goes for other items. Run your smoke tests isolating things in question.

[gadget73]

that almost looks to be rolling out of the boot around the brake rod. If the booster were shot you might get this. Easy test, crimp the booster vacuum line off and see if it stops. I'd expect to hear a noticeable sucking noise if it were the booster.

if the vac line for the half moon thing were totally unhooked it might do this.

Doubt the cruise would do it since there wouldn't be any connection to the vac dump from the manifold when the cruise wasn't engaged.

[bgreywolf]

The cruise dump valve could be misadjusted. I had that problem on the F150, if I picked up the pedal a smidgen with my toe the hissing would stop. I thought it was the booster, got under the dash to start disconnecting things and saw the dump valve open from just the weight of the pedal. Saved a lot of time and money; adjusted the valve (instead of replacing the pedal bushings and so on...the thing had about 400k miles as a Texas construction truck, about most of them before I bought it in 2005).

I'd just put a rubber cap on the manifold connection for the cruise, and under the dash at the parking brake release. If there's still smoke, check the booster. If not, decide whether you use cruise or the parking brake release or you'd rather sort out the performance first.

[BlackVic_P71]

Ok, clamped off the vacuum line to the booster...no smoke.
Looked at the lines for auto-release of the parking brake, no.
There is a line over the brake, I clamped that off and now see no smoke.



F*ck it all and f*cking no regrets