coolrotariesR1

iTrader: (2)

Would anyone know if the brake master is supposed to relief pressure when the car turns off? I noticed a small hissing sound where the reservoir meets the round black part of the booster when I turn the car off. Not sure if it's normal. There isn't a gasket in the matting part.

DaleClark

iTrader: (55)

Not sure, good question. That's the brake booster there, it does use engine vacuum to do its thing.

If your brakes work properly, everything runs right, don't worry about it.

Dale

Pete_89T2

iTrader: (4)

Well the brake booster should hold a vacuum after you shut off the car. If you're hearing a hiss that sounds perhaps like a leaky air compressor hose for a short time after you shut off the car, it's possible that the booster is leaking somewhere. In this case, the sound you hear is air filling the booster's vacuum chamber volume until it reaches atmospheric pressure. Possible likely causes for the leak could be anywhere on the brake booster hose, its fittings/clamps, or perhaps the plastic check valve that should be inside the hose may have failed or is missing.

quichedem

iTrader: (4)

Dale nailed it. I would fix that as soon as possible.

coolrotariesR1

iTrader: (2)

Thanks guys I'll have to investigate further on this. It's definitely leaking air between the booster and the master. I put my finger towards the bottom of the matting area and I hear the hissing sound change a bit. Will check the pedal pressure and report back. From what I see from another thread is that maybe the diaphragm might not be sealing properly. We'll see...

billyboy

One of the 4 or 5 masters here had a thin paper gasket installed and it looked oem - we've had no issues running without one on the other hand.

Soap and water, is a simple handy indicator of pressurised leak sources.

TwinCharged RX7

iTrader: (14)

Just FYI. I've called many brake repair shops that do booster rebuilds. The brake booster is NLA and no one will rebuild them either. Hope you have better luck than me.

In a pinch, you can buy the RHD version and just use a longer hose.