924Board.org

[Benino]

1980 924 N/A

I'm pretty sure I need to replace my brake master cylinder. many times as I sit at a stop light my break pedal sinks all the way to the floor and I have to pump it to get it back up. I recently bled the breaks so there should be no air in there. anyway. . .

I was wondering if there is a better master cylinder I can get that would bolt up instead of just a replacement stock one. will a 944 master cylinder fit there? if not is there a better one I can put on there without having to make modifications?
_________________
1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

[AznDrgn]

it would help to tell us what brake setup you have. 4 wheel disc? or drums in the back?

If you have drums I believe it would be an upgrade to go with an early 944 master cylinder since it has a larger bore. You would need to change your brake lines or modify them to fit on the new cylinder though since the lines go in different places.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[Smoothie]

Unless you're changing other brake components that require a different size MC, I would stay with the OE version and either rebuild or replace it. According to my book, rerouting and rebending brake lines isn't something to be bothered with unless it's really necessary.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[gohim]

Do you have drum brakes in the rear?

If so, when was the last time that you adjusted them?

The rear drum brakes that come standard on 924 NAs, are not self-adjusting. Because the brakes are piped diagonally (left front to right rear, and right front to left rear) when the rear brakes are not adjusted regularly, the front brakes will not work properly either.

You end up having to pump the brakes to make them work, and the pedal is not firm when you do.

So, if your master cylinder is not visibly leaking, and you have not been adjusting the rear brakes regularly (about every 6-8 weeks), the master cylinder is probably still fine. You need to adjust the rear brakes and keep adjusting the rear brakes on a regular basis.

The only way to get away from this is to convert to four wheel disc brakes. Replacing the master cylinder is not going to fix this problem.

The 944 master cylinder has the same 23mm+ bore as the 924 master cylinder, so it really isn't an upgrade. No upgrade is necessary.

[Benino]

could that really be it? sometimes the pedal travel is just a few inches and then sometimes it's like 1/2 or 2/3 the way down to stop the car and then once I stop and am sitting at the light idling with the brake on, the pedal will start sinking until it's all the way on the floor. Could that be the rear drums? if so I'll adjust them asap. . . it's just a pain because of the huge nut w cotter pint which has to be so damn tight.
_________________
1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

[gohim]

You don't remove the rear drums to adjust the rear shoes.

I'll bet that your parking brake does not work either.

There are two slots in each of the rear drum brake backing plates located so you can reach the adjusting star wheels, and two adjusters for each drum (one for each brake shoe).

Since you don't know that the rear brake shoes need to be adjusted every couple of mnths (at the least), obviously you don;t know how to do it, and you don't have a Service Manual of any flavor.

I suggest before you do anything else that you spend $15 and at least buy the Haynes Manual, and take the time to read it cover to cover.

The procedure that I used to adjust my drum brakes (when I had them on the 924) was to place the transmission in neutral, then lift one rear wheel off the ground with my floor jack, pull the braking park handle up two clicks. Using a screwdriver, back both brake shoe adjuster off, until the shoes are not dragging on the drums. Then adjust each brake shoe until it starts to drag on the brake drum. Now pull the parking brake handle up three more clicks. Grab the associated wheel and try to spin it with both hands. The wheel should be locked up tight. If you can turn it, then you have the shoes adjusted too loose still. If the wheel is tightly locked up, release the parking brake, and make sure that the wheel can turn freely, with the shoes barely making contact with the drum. Readjust if necessary, and if it's okay, lower that side of the car, raise the other side of the car with the floor jack and repeat the process.

[Sleykin]

WOW!! My 1940 Chevy 1/2 ton had brakes like that <LOL>
If you adjust one star too far and the other not enough it would blow the piston out of the slave cylinder. So much for the "good ol days"
_________________
Glenn Neff
Medford, OR
87' 924S

[Joes924Racer]