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I took all four wheels off myself and didn’t notice anything strange, no leaks, nothing wet, etc. So I brought the car to a local mechanic and he also can’t find an issue. So I figured maybe just replace the master cylinder and go from there? The car is a 1991 N/A non-ABS rx7. I still have pressure in the system and the car still stops. He said the brakes still had over 50% life left and would pass inspection and everything looks good there.
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That’s a fair amount of fluid to be losing each week. Should be able to find where it’s going. Trace all the lines and check all fittings and things like proportioning valves. Follow all the lines to the master and if it’s leaking that much fluid you should be able to see a trace of a leak.
Well there is no fluid anywhere on the lines according to the mechanic. It’s near impossible to see the hardlines against the firewall because they are behind the engine and covered with everything. I’d have to remove the engine to get to them. All the fittings and rubber hoses arent leaking anything.
[quote=”ryan2949″ post=49695]What could the brake booster be doing to cause a leak?[/quote]
Pull the vacuum line from the brake booster and look inside. if you have fluid inside the booster then you have a leak at the rear of your master cylinder. you will need a new master cyl. will also want to remove the fluid from inside the booster
[quote=”619DioFan” post=49752][quote=”ryan2949″ post=49695]What could the brake booster be doing to cause a leak?[/quote]
Pull the vacuum line from the brake booster and look inside. if you have fluid inside the booster then you have a leak at the rear of your master cylinder. you will need a new master cyl. will also want to remove the fluid from inside the booster[/quote]
As he said, its probably the master cylinder
[quote=”619DioFan” post=49752][quote=”ryan2949″ post=49695]What could the brake booster be doing to cause a leak?[/quote]
Pull the vacuum line from the brake booster and look inside. if you have fluid inside the booster then you have a leak at the rear of your master cylinder. you will need a new master cyl. will also want to remove the fluid from inside the booster[/quote]
+++1 🙂
Thanks everyone. Unfortunately I can’t look into the brake master because what connects the vacuum hose is a 90 degree bend. My girlfriends dad who’s a heavy duty mech. also said that was most likely the problem and to dip something into the booster and see if it’s wet.
Will report back with results.
Not sure what happened but we looked for leaks and found some places that might be the culprit but because it’s the middle of winter here we weren’t sure as the car’s undercarriage is covered in ice and slush/snow. So I let the car sit over night in a heated garage and we checked again (this was a few days later after we checked the first time) and we noticed no leaks after pressing the brakes for a long period of time, over and over. We bled the system for a second time and the brake pedal feels back to stock and we haven’t noticed any leaks…
I didn’t think you’d notice anything by removing the vacuum hose for that very reason. Personally, I’d unbolt the master from the booster and see if it’s leaking there. You don’t have to disconnect the brake lines, you can just unbolt the master and pull it forward to have a look. It wouldn’t be the booster that’s leaking anyway, it would be the master cylinder leaking INTO the booster. If it’s not leaking there it may be leaking into the ABS. I have seen some systems do this when a valve in the ABS goes bad. Keep us posted.
It’d be the master cylinder’s secondary cup seal on the primary piston that’s leaking onto the booster. The booster connects to the master cylinder by a pushrod. If you see fluid on the booster shell or even the appearance of the boosters paint eaten away then that’s the issue. Did you thoroughly check all of the line fittings going into the calipers or wheel cylinders? Really hope for your sake it’s not the ABS module.
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