Brake vacuum reserve

[colinnwn]

Hey Everyone,

 

My Pathfinder just quit holding vacuum with the engine shut off, so I am unable to press the brake before starting without lots of effort. The likely suspect is a leaking vacuum reservoir. But I know it could also be a leaking brake booster, or a leaking vacuum line. Anyone have experience with this happening on a Pathfinder? Are there any likely reasons besides the obvious ones?

 

Thanks.

[alexrex20]

after you shut the engine off, there is no vacuum. you can pump the brakes once or twice before losing all pressure in the booster. maybe you've already exhausted the stored vacuum in the booster (by hitting the brakes with the engine off), by the time you try to start it again.

[colinnwn]

Nope, I don't touch the brakes after I turn the engine off. I usually pull in and stop, pull the parking brake, take my foot off the brake, and cut the engine. I was aware there should be 2 reserve brake actuations after the engine stops and then no more. I haven't tested how long it takes for the vacuum reserve to bleed off (a few seconds or a few hours) but I know it used to last my 9 hours at work, and now it won't.

[alexrex20]

check the check valve in the fitting which connects the vacuum line from the intake to the booster housing (of course, check the entire vacuum line as well). air should flow through it in only one direction. it's rare for the booster itself to fail, especially on a vehicle as new as yours.