Brake issues....

[4wdEconoBox]

So I've been fixing small quirky things on my 87 and one thing I haven't figured out yet is the brakes... They feel firm after 1 pump if the engine is off, but when the engine is running they feel really realy soft no matter how many pumps. Much worse than my 85. The 87 still stops fine, but just gets a little scary if I have to stop in a hurry. Apparently it's had a squishy pedal for years, bc the PO replaced the master cylinder and rear wheel cylinders in July of last year. I've bled the brakes at all 4 corners, checked the brakes( not in the best shape, but not bad enough to cause problems). The fluid is a little darker than normal but not brown.

So what could cause this problem? Could a bad brake booster be the cause, allowing too much vacuum assist? Anyone have any ideas or tips or any tests I can try? Or am I just going crazy?! Haha

[irowiki]

By bleeding the brakes, did you get rid of ALL the old brake fluid?

On my 83, it was having strange issues like randomly having no brake force. So when I bled the brakes, I only bled out of one wheel until the fluid was brand new and the master was full of new fluid, then did the rest of the wheels, making sure all the old gunky fluid was out, and it worked like a charm after that!

How's your rear brakes? Like if you put the brakes on while going backwards, how does it feel?

[dlb]

does the park brake work properly? park on a steep hill and see if just the park brake can hold the car. if not, the rear brakes are out of adjustment. this could be due to frozen park brake cables which prevent the auto-adjusters from working, or the adjusters themselves could be frozen. i've usually found the cables to be the cause.

failing that, bad master cylinder is my guess. quite a few people here have had problems with remanufactured master cylinders. do you know if the MC put in was new or a reman?

[Petros]

sounds more like it still has air in the system. It takes a lot of pedal pumping and bleeding to replace all of the old fluid, and any air bubbles, caught in the system. I presume you know how to bleed it so no air gets back into the system.

Start with the right rear brake, pump and hold, bleed, than pump and hold, etc until you get fresh fluid. It might take as many as 20 iterations to get it all out. than go to the left rear brake, it should take much less than the first one. than the right front brake, and so fourth. You might also try "bench" bleading the master before you start. You are supposed to do that before you install it but many people neglect this important step, you can do it in the car, you just have to take off both brake lines. You need a kit to do it, usually comes with most new master cyclinders, I am sure any auto parts store will have it. It will not cost much, just some plastic fittings and a few short lengths of clear plastic hose, likely less than $5.

If you still get bubbles the master could be bad. I had that happen more than once, a new out of the box remanufactured master added more air to the brake fluid than the old leaky one. If you can buy a new master, not a remanufactured one. Or rebuild it yourself from a kit (easy and far less costly). A bad master is very frustrating because you are assuming the "new" part should be good, and it you check or replace everything else and the problem is still there.

This delayed me driving home once, I bought a Tercel from another forum member in the LA area, and did some extensive repairs to it in my dad's garage (clutch, brakes, new head gasket, etc.). the local auto parts store could only get remanufactured master cylinder so I took it. After the car was all together and I was bleeding the brakes (one of the reman rear wheel cylinders was also bad, so I took it apart and the old one, and made one good one out of it using the new parts). Than with my 80 year old dad pumping the pedal I keep bleeding and bleeding, but pedal stayed mushy and I still got a steady stream of bubbles out of the now clean new brake fluid. I took out the master and bench bled it again, this time it too gave off a steady stream of bubbles just like I was getting at the wheel bleeders. I took it back to the store and they were able to get another one by the next morning, when I was supposed to leave to get home. The replacement master was in my 8 am as they promised, and I had the car ready to go by mid day. But all of the wasted time with the reman was NOT worth any savings, it was just that the local auto parts store no longer had any suppliers that sold new master cylinders for our year cars. They are still available, it was just there was no auto parts store within 20 miles that could get one the next morning. You can get them from Rockauto.com at a good price, but next day shipping from them is very costly, so if you can plan ahead that is the best place to get them.

good luck.

[4wdEconoBox]

Sorry guys, I've been busy the last few days and haven't done anymore tests on it so far. I haven't changed all of the brake fluid out, I might do that today if I can get my little brother to help me pump the brakes haha. Is there anyway to tell if the MC is a reman or a new one?

I might take a trip to a parts house too and get a kit to bench bleed the MC, I need a big bottle of brake fluid anyway!

[dlb]

you don't need a kit to bench bleed the MC. you don't even need to remove it from the car to bench bleed it. just disconnect the car's brake lines from it, connect some short spare brake lines to it, bend the ends so they are sitting in the reservoir below the fluid, and have an assistant slowly pump the brake pedal until bubbles stop coming out. that's it, then you remove the spare brake lines and reconnect the vehicle's lines.

it's essential to bleed all old brake fluid out of the system whenever you do a brake flush. brake fluid is hydroscopic, which means it attracts water over time, and that corrodes the brake lines from the inside out. brake fluid should be replaced every 2 years, i think? something like that. some after you bleed the MC, bleed all 4 brakes until the fluid is translucent gold. maybe you will get lucky and that will fix your spongy, weak brakes.

[4wdEconoBox]

Yeah, thats exactly what I ended up doing dlb. I flushed everything and I missed a leak I guess.... The rear passenger side wheel cylinder is leaking, so I guess its time to get new ones. I'll just add it to my rockauto order haha. I'm debating on either rebuilding the master cylinder that I have, or buying a new one. I don't mind rebuilding it, but my question is, would that be just as good as a new one, or should I just fork up the extra money and get a new one?

[dlb]

nothing wrong with rebuilt as long as it's done right. i wouldn't rebuild it until you replace the leaking wheel cylinder and test the system though. no point in rebuilding it if it's working fine.

[BaileySims]

I had the exact same problem on mine when I picked it up awhile back. I missed a leak in the same dam spot yours is in. Replacing that wheel cylinder fixed it for me. Let me do some looking really quick. I might have one that fits your car. I bought the wrong one the first time and didn't feel like sending it back.

[Petros]

New rear wheel cylinders are relatively inexpensive, and usually worth the extra cost over a kit (the wheel cylinders sometimes badly rust out and no amount of honing helps).

the key to a proper rebuild of the master is to hone the bore properly. Than clean it very well to get all of the grit out. Note that if the old bore is pitted that the hone should take care of most of it, I have noticed however any deep pits can be left in place rather than hone them out to get it completely clean. If you bore it out so the deeper pits are gone it may not seal properly, but a few pits do not seem to harm the performance of the master if it is honed smooth. If it is badly pitted it can be sleeved by a machine shop, but replacement is a more practical solution.

Also, lube the parts with brake fluid before assembly, and push the pistons in very carefully so you do not damage the lip on the new seals. than remember to bench bleed the master.

[4wdEconoBox]

Yeah, I'll definitely replace that wheel cylinder before I rebuild the master. I took the drum off a few minutes ago, and apparently it wasn't replaced when the other one was, even though the receipt from the shop said it replaced both wheel cylinders...Which is why I didn't pay much attention to leaks when I was checking everything out...

If you've got one that fits mine that would be great Bailey! PM me if you find it and its the right one!

Hopefully I won't have to rebuild the master though, it seemed to bench bleed just fine, no bubbles kept coming out after I was done, so hopefully that means it'll be fine!

Thanks for the help y'all!