Vacuum leak?

[cmgaudette]

I’ve got leak in my brake system ‘82 series 3. Idle goes up when I step on the brake and it’s getting tiring trying to adjust for it. I’ve actually put hylomar on the vacuum tube into the servo but it’s done nothing.
I’m about to buy a new servo thinking the diagram is toast but am I missing something?
Would love some insight before buying another new part.

[biffidum]

You could jam a plastic cap into the booster vacuum line and test drive to see if the engine performance stabilizes. This would help isolate the problem to the booster. Double check your vacuum line connections (carb, dist.) and check hoses for cracks if the booster is not at fault.

[roverp480]

The fact the the idle is OK with the brake off would seem to indicate to me the vacuum line to the manifold and its connections is OK . Does the Servo hold a vacuum with the engine off? I would have thought if the booster diaphragm is leaking , the servo would not work or would only offer a short period of assistance.

[cmgaudette]

I’ll pull the line and cap it tonight after work. Seems like the diaphragm may be the culprit. Besides that I’m happy to see her running well

[cmgaudette]

So if I pull the line off at at the servo end and cap it the idle smooths out perfectly. Guess I’ll be replacing the servo next week.
Is there a way to rebuild it? Or just replace the diaphragm?

[biffidum]

These are not typically serviceable. There is a remote chance that the "can" has a rust hole which is breaking the vacuum. You could repair the hole and all should be good. Worth a look.