SoxSider

Well guys, on my way home from getting a paint quote on my RX7, my brakes went bad. When I was on my block, I did a little bit of a clutch dump and then slammed on my brakes when I got to my house. Guess that killed the brakes...

Now the pedal goes to the floor and there is hardly any stopping power. I checked the fluid in the brake master cylinder and it was filled to the top, so I think the lines are okay. The brake light is on though...why I don't know.

Does anyone have any ideas of what it might be?? Any help is appreciated. I've never even done any mechanical work on a foreign car in my life and I don't have much time and money. I'm starting to have doubts about this car that I thought wouldn't give me any trouble...

speedracer_not

mine did the same thing. One of the rear slave brake cylinders went kaput, but they still had some stopping power. So that makes me think that a front brake slave cylinder went bad.

First thing I did was replace the master brake cylinder which didn't help. Lesson learned is visually inspect the all the slave cylinders and verify the culprit before swapping out "stuff". Then again it could of been the master brake cylinder, the metal brake lines, or the rubber brake hoses....disc brake shoes or rear drum brake shoes.

mazdaspeedrex

First off there is only one slave cylinder on the car and it is part of the clutch hydraulics not the brakes. What speedracer was probably referring to are the front brake calipers and rear calipers(disc brakes) or wheel cylinders(drum brakes). Yes you should check all 4 corners for leaks before replacing anything. Only 2 things will cause a complete loss of pedal; a loss of pressure due to a leak or a bad seal in the brake master cylinder. The brake light comes on for 2 reasons; your park brake is engaged or you have low fluid. If you're sure the park brake is down, recheck the fluid level.

If you don't find any leaks at the wheels, look at the rubber brake hoses and steel lines. If you have a helper press the brake pedal while you look you might see a leak easier than just looking for wet spots.

If, after repeated application of the brake pedal you don't see a leak underneath the car, check on the brake booster under the master cylinder. The seal can go bad and leak fluid out of the back of the master, dripping down the booster. If there is no sign of leaking anywhere and the fluid level is still ok, then blame the master cylinder.

74RX4

iTrader: (10)

If fluid is not draining then you probably have an internal leak in the master cylinder. I would look at each of the rubber lines that connect to the calipers for fluid leaks to be sure. Check the large vacuum line that goes to the booster behind the master cylinder. A leak in it or a stuck inline check valve can cause low braking power, but usually its the master cylinder.

SoxSider

I just checked everywhere for leaks and there don't seem to be any. The more I read around online, the more I think it's gotta be the master cylinder.

Also, when I started the car again to pull it into my garage, the brakes were firm again and had good stopping power. I think it could definitely be a vacuum thing because the previous owner had removed the rats nest, and I think he might have messed with some vacuum hoses when he did that. It would make sense because wouldn't beating on the car directly before the brake issues occurred have something to do with the vacuum running harder/differently?

Anyways, I'm gonna replace the master cylinder for sure. Does anyone know where I can get one the cheapest? I'm really low on money right now and the cheapest I saw online was around $85.

speedracer_not

[quote=mazdaspeedrex;10094289]First off there is only one slave cylinder on the car and it is part of the clutch hydraulics not the brakes.

DarrenTRS

iTrader: (1)

A failed brake booster would only cause the pedal to be harder.

Rockauto.com has a Bendix brake master cylinder for $19.87 but you will have to swap over your reservoir.

speedracer_not

http://www.oreillyauto.com/site/c/de...1292&ppt=C0066

$27 ??? But I'd get that $85 one, replacing and bleeding the master brake cylinder is allot of tedious work.

SoxSider

Thanks for the help guys. Looks like I can get the part for pretty cheap. Hopefully it won't be too bad to install. Is there a writeup anywhere that walks you through the installation?