I've had an issue with the brake booster slowly loosing vacuum when the car sits overnight. I started with the easiest thing which was swapping out the check valve and gasket in the vacuum line. It wasn't that - the valve was still good. It could be the o-ring on the intake manifold, but that doesn't look to be replaceable. It's embedded in the intake and no part for that o-ring is listed on RealOEM.

There are no issues when the car is running - brakes feel normal and no problems with the engine revving when applying the brakes.

I took a closer look around the booster and there is some corrosion and marking near where the brake master cylinder meets it. Could be a leak - could be from brake fluid spilled over the reservoir when swapping the fluid out over the years I guess.

Any suggestions on narrowing down the slow leak before I commit to the next repair? Replacing the booster does not seem like an easy job just looking at the Bentley instructions, and it's pretty expensive too.

 

Could it possibly be the slave leaking?
Are you losing fluid at the reservoir?
Perhaps pressure bleeding one of the brake lines might show if there is evidence of a leak from the booster??
Maybe wipe down the area clean where you suspect the booster may be leaking and see if there any signs of new drips/runs before you commit?
I am hardly an expert but agree - I too cringe at the cost and/or having to replace the booster.

Sorry I'm not much help.

 

Yep, check those places out.

You can get the oem ate one aftermarket now :
https://www.ecstuning.com/Search/Sit...h/34336779679/