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I remember reading some where some one replaced their master cylinder with a bonneville mc which had portioning out the wahzoo.. my master cylinder is in dire need of replacement due to the air trapped in it that i don't have a scan tool to remove.. if anybody knows which bonneville mc will bolt right up please LMK i need my brakes to work ASAP


also if anybody knows how to bleed the master cylinder without a scan tool that will be greatly appreciated

no luck aye guys?

i guess imma have to try and locate one that will fit.. any body know what year i should start with?

If you dont have a brake upgrade dont get a bigger master.

there should be two bleeder screws on the master cylinder...

Bonneville (H body) MC on a J body booster with a  Summit proportioning valve and a SSBC gauge.


An F body MC will also bolt right up (same size- 1", just the ports are on the passenger side). I've also heard a Jimmy/Blazer one will fit too, but the H/F body one is larger.

I'm under the same- unless you have a reason for it, don't bother- premise. I run a full H body setup in the front of my car, and Neon discs in the rear.

If you get a larger master with the same size pistons on the calipers you will have less braking power. The only reason to get a bigger master is if the calipers require more fluid.

(ericm555 @ Sep. 09 2006,07:26)Q
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EIf you get a larger master with the same size pistons on the calipers you will have less braking power. The only reason to get a bigger master is if the calipers require more fluid.
Not true. Using a larger bore MC will not reduce your braking power at all. It will only reduce pedal travel and force required to push the pedal.

When increasing the size of the caliper pistons (or adding more), yes, more fluid is required, but only the size of the reservoir has to increase, not the actual MC bore size. When you upgrade to a larger caliper piston, it only makes sense to upgrade the MC bore size, since using a smaller (stock) diameter will have increased pedal travel and more pedal effort to fill the extra volume of the bigger (or added) caliper pistons.

If you run stock size calipers, you can run a larger MC if you want increased pedal response and feel. I don't recommend it, unless you know how to play with proportioning (which isn't super difficult), and know how to re-plumb the system to reflect the new MCs proportioning.

I grabbed a master cylinder from an 03ish 2.4 grand am, they dont have abs and instead have a proportioning valve hidden up near the rad, IIRC. The brakes are 1000x better on my car, it was probably one of the best mods I've done.