brake pedal hiss

[subtlt]

Hi guys,

Stockish 87 GN, powermaster brakes, new acc ball. no warning lights.

There is a "hiss" coming from the brake pedal area. If I press down the pedal it goes away, but as it comes back up, the hiss starts. If left to sit for 10-15 seconds it goes away.

I'm going to work through the PM diagnostic tree, but it seems that if the warning light doesn't come on, it assumes the system is OK?

Brakes work fine, no hard pedal etc.

My guess is the PM master is leaking internally?

Any tips welcome!

 

[subtlt]

m/c rebuild time

It looks like the system won't hold pressure and is leaking internally. Only holds for about 10 seconds before the pump comes on again to top it up. I'll rebuild the MC, and I think that will solve the problem. The pump pressures up within spec times. Fortunately, the rebuild kit is still available from GM for $38.

May have to contact Hank for the pump if it doesn't solve the problem.

Thanks for the PMs.