Got my car back from the shop after having yet another engine put in and the brake light is on intermittently, mechanic takes a look and says the right rear wheel cylinder is leaking and needs to be replaced. So I grab the part but before i can replace it i loose almost all the breaks, upon inspection the master cylinder is leaking fluid on the rear side, pressure switch?, and the plastic diaphragm is not connected to the cover. My question is does the master cylinder need replacing, i know there have been many issues with the stock ones, or is this just a symptom of the fluid leaking at the wheel cylinder. If the master cylinder does need replacing, what is the best option? Vacuum conversion or rebuilt stock part?
Brake Fluid Leaking from Master Cylinder
- Thread starter cdub
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I'm thinking the leak may just be from overfilling, the mechanic put more fluid in the res when i asked about the brake light, so when it pressurized the accumulator it prob just had to bleed out. Given the know air in the system from the bad wheel cylinder i'm still hopping I can get away with replacing the cylinder and doing a full flush/refill/bleed.
I haven't been able to locate a flush procedure, just bleeds, a link to one would be much appreciated. Thanks to Zues for all the great info you have posted, learning a lot for them.
I haven't been able to locate a flush procedure, just bleeds, a link to one would be much appreciated. Thanks to Zues for all the great info you have posted, learning a lot for them.
Swt_86
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- Joined
- Aug 30, 2002
- Messages
- 293
If your resevoir cover is not on securely, you most certainly will have brake fluid all over your firewall and the back of the master cylinder as you described. Also check the fluid levels and make sure it isn't over filled. Remember that the resevoir on the passenger side (the largest of the three) is for the PM accumulator. With the key off, pump the brakes at least 10 times before checking the fluid level. This will discharge the accumulator and give you the true fluid level. Follow the diagnostics that I sent you. They helped me. Good luck.
Cap was definetaly on tight, could it come loose due to overfilling with fluid? Perhaps this is where the fluid i see on the rear of the PM is coming from? Still looking for a procedure to completely flush the fluid and replace with new. Thanks for the diag info I will go though it and hopefully i can find my issue.
With ignition off, pump brake pedal 10 times to empty brake fluid from accumulator ball.
Then open the reservoir and carefully take out all the old brake fluid with a turkey baster. Refill to the appropriate levles for each side of reservoir with Valvoline Synthetic.
With ignition off, then bleed each wheel cylinder- make sure that the reservoir stays full as you bleed. This requires 2 people. When you get all the air out of the system and the brake pedal feels good, you have flushed the system. Make sure that the reservoir is appropriately filled but do NOT overfill the system.
Carefully test drive.
Frank
Then open the reservoir and carefully take out all the old brake fluid with a turkey baster. Refill to the appropriate levles for each side of reservoir with Valvoline Synthetic.
With ignition off, then bleed each wheel cylinder- make sure that the reservoir stays full as you bleed. This requires 2 people. When you get all the air out of the system and the brake pedal feels good, you have flushed the system. Make sure that the reservoir is appropriately filled but do NOT overfill the system.
Carefully test drive.
Frank
Swt_86
Member
- Joined
- Aug 30, 2002
- Messages
- 293
Yes, overfilling can cause fluid to leak out between the resevior and cover.
I'm pretty sure this is what happened then, so hopefully i can replace the wheel cylinder, flush the fluid and be good to go.
Most likely 2 separage problems. Wheel cylinder can be replaced independently of the P/M. As mentioned above, if you pump bleed, do it with the ignition off (preferably). Most mechanics that don't know the P/M will fill the p/s bowl full. It should only be full with the acc pumped down - about 1/2 full with the acc pumped up.
Most likely what happened is that you have a problem in the P/M and the full bowl spewed when you acc pumped down. The acc ball empties back into the bowl when pumped down. You need to run diagnostics.
Brake System
See my sig for bleed/flush procedures. In essence the same thing.
You flush in new fluid by bleeding the system.
You're welcome for any help I have been.
