When was the last time the brakes were bled? That is another thing as well, but if there is some component failing, allowing air in to the system, that would account for what you are describing as well.

I would still put money on master cylinder though, especially if it has been replaced with a reman unit.

The brakes were bled 3 years 30k miles ago

Master cylinder is factory

Yes, usually you will feel it losing it'* pressure as you hold it. But with power barkes it can be the diaphragm, not a fluid leak.

Just had a inspection done at pepboys you guys were right slow leak on the rear seal of the master cylinder they are bleeding th brakes now and Im going to order me a new one and attempt to install it

Thread moved to Pontiac section.

is this pretty strait forward on how to replace the master cylinder in most cars. or would my grand am be different
http://youtu.be/MylnRsioeRA

what should i buy cardone or dorman?

Which ever one has lifetime warranty? If they are remans, you will be replacing them fairly regularly, if it is new, not sure.

bought the cardone as it was new car is being sold this year or early next so im not worried about lifetime warrentys i think it has a few years though

its 3 years car will be long gone by then