Need Help: brake master cylinder leak

[watermellon]

Hi, I have a 93 festiva with fuel injection. I have a fluid leak where the brake master cylinder attaches to the power brake booster. Does that mean a gasket needs to be replaced or does it mean my master cylinder is shot.

It's been leaking for a couple of months now, and whenever the reservoir gets low I have just been topping it up with some dot 3 brake fluid.

If it is just a gasket do I just remove the 2 mounting nuts and install a new gasket? Would I have to drain all the brake fluid and bleed the brakes? If someone can help me... please do. I'd greatly appreciate your help.

[kartracer46]

The master cylinder is failing, it needs to be replaced. You will have to bench bleed the replacement master cylinder. Then you will need to bleed the system at each wheel once the new master cylinder is installed.

[Larry Hampton]

+1

[Damkid]

ditto :lol:

[1990new]

Got this in my email from RockAuto a few days ago.

Part Type: Master Cylinder

• Manufacturer: EIS
• Part No: E150252
• Notes: New Master Cylinder 3/4"
  Closeout Price: $47.89Only 11 Remaining!

• Manufacturer: BECK/ARNLEY
• Part No: 0728485
• Notes: [Brake Master Cylinder];
  Closeout Price: $52.99Only 1 Remaining!

• Manufacturer: BENDIX
• Part No: 12392
• Notes: Hatchback
  Closeout Price: $53.79Only 1 Remaining!

[91mcnasty]

What they said!

[Gomez]

I think it takes 5 people to say the same thing before it comes true.

5th one here. MC failing. Signed into law.

[TominMO]

Snag that M/C!

[watermellon]

Thanks for replying everyone. It seems like its going to be a lot bigger job than I thought it was going to be. I'll give it a try and hope for the best.

[Banana Bonanza]

The hardest part is removing old plastic resevoir from old master and installing it on new one. You then bleed the master cylinder off the car, doing it with master clamped in vise is easiest but I've done enough of them right on ground in driveway. The new master will come with couple plastic fittings and couple tubes that hook to the fittings and then go into the resevoir. Push on piston with screwdriver in and out until bubbles are gone in the resevoir. They include instructions to do this with the new master. Then if you are careful, you can install it without bleeding calipers/wheel cylinders. Trick is not to get any air in the lines. You only need to bleed at the wheels if you have low or spongy pedal after installation. If pedal feels fine, then you are done.

Ok just looked at RockAuto and apparently the master cylinders now come with the plastic resevoir installed. Finally somebody got smart! That is great. I hated trying to pry off old partially brittle plastic bottles. Very good chance of breaking it. I had an ancient Courier once and rather than deal with rare expensive master and plastic bottle sold separately, I adapted an all cast iron master from a 67 Chev pickup to it. The Chev master was like $11 back then.

[TominMO]

The one I got at O'Reilly's had the reservoir installed too.

[boydg1]

.... X2 on this installation. I too had problems with the plastic like reservoir. On the first replacement while bleeding I could NOT get the FRONT connection to pump. On the second replacement the front and rear connections pumped OK BUT the the reservoir tank was leaking around the front rubber grommet. The reservoir tank sat loose in both the front and rear grommets. So, I very carefully pried equally on both grommets untill I removed the tank. Then, I put an "O" ring on both shafts of the reservoir tank and reinserted the reservoir tank back into the grommets on top of the master cylinder. Bled it again, and still had a leak. This time it was in the white plastic like material directly above the front grommet adjacent to the tank itself. I put a little RTV in the corner there at the side of the tank and that did the trick. (see pics).
.

.... Had to use a magic marker to make a black dot on the tank because the camera didn't have enough contrast.
.


.

The hardest part is removing old plastic resevoir from old master and installing it on new one. You then bleed the master cylinder off the car, doing it with master clamped in vise is easiest but I've done enough of them right on ground in driveway. The new master will come with couple plastic fittings and couple tubes that hook to the fittings and then go into the resevoir. Push on piston with screwdriver in and out until bubbles are gone in the resevoir. They include instructions to do this with the new master. Then if you are careful, you can install it without bleeding calipers/wheel cylinders. Trick is not to get any air in the lines. You only need to bleed at the wheels if you have low or spongy pedal after installation. If pedal feels fine, then you are done.

Ok just looked at RockAuto and apparently the master cylinders now come with the plastic resevoir installed. Finally somebody got smart! That is great. I hated trying to pry off old partially brittle plastic bottles. Very good chance of breaking it. I had an ancient Courier once and rather than deal with rare expensive master and plastic bottle sold separately, I adapted an all cast iron master from a 67 Chev pickup to it. The Chev master was like $11 back then.