I've failed

[kingston]

Well, it looks like I'm going to have to give in, and have to take my E30 to the shop.

A few weeks ago, I noticed that my brake pedal seemd to be sinking a bit. Soon after, I started having the pedal fade pretty quickly and I would have to pump the brakes to come to a stop.

I replaced the Master Cylinder with a used one (supposedly good, but I don't know). I bled the brakes with a power bleeder and afterwards they were better than they had been, yet still not as good as when I got the car.

Soon after the pedal started sinking to the floor again. Now I have pretty much no brakes. I've bled the brakes several times to no avail.

I thought that the ABS pump might still have some air in it, so I went for a drive and did some hard stops to get the ABS to kick in. However, it never did. My wheels would lock up without the ABS engaging.

So now I don't know if I have a bad ABS pump, ABS relay, Master Cylinder, etc... and I guess I'm taking the car to a shop, unless anyone else has any bright ideas.

Thanks doodz

[Farbin Kaiber]

Does your brake booster hold vacuum? Are any of your calipers leaking? Are your brake hoses old and seeping air into the system?

[george graves]

Find someone local to help. These e30's are stupid easy to work on once you know a few things.

Answers farbins questions - they all might seem random, but he's on it.

[Dude]

Find someone local to help. These e30's are stupid easy to work on once you know a few things.

Thisthisthis.

[ZM Blue Devil]

open and check the abs relay, see if the solder is broken(common and easy fix)

[kingston]

Guys, THANK YOU for your responses!

Does your brake booster hold vacuum? Are any of your calipers leaking? Are your brake hoses old and seeping air into the system?

I'm not sure how to tell if the booster is holding vacuum. Can you please inform me? My understanding was that the pedal feel would be very hard if the booster was kaput.
There is no sign of fluid leaking from either the calipers or the lines, although I suppose that does not mean that air couldn't be leaking IN. However, I can test the brakes IMMEDIATELY after bleeding them, and they won't work at all. I think it would take at least a little time for enough air to get in to make them THAT bad.

Find someone local to help. These e30's are stupid easy to work on once you know a few things.

Answers farbins questions - they all might seem random, but he's on it.

That's great advice. I did meet a few people at a small E30 meet a few weeks ago. I will reach out to them. And I'll answer any questions posted here, as folks are trying to help me!

open and check the abs relay, see if the solder is broken(common and easy fix)

This is new advice to me, and I will try it. A quick search makes it look like that relay is located under the dash. Is this correct? And I assume this would help me get to cycle the ABS pump, but might not explain the soft pedal.

If I nail the brakes HARD, they seem to work for a few seconds and I can lock up my wheels, but then they fade FAST. If I push down slowly, the pedal goes to the floor.

Thanks again guys; I truly appreciate the responses!

[kingston]

I neglected to mention that I tried pumping the brakes several times while watching the master cylinder. With the pedal falling to the floor several times, I see no change in the fluid level in the reservoir. Don't know if this is another clue or not.

Thanks again!

[Farbin Kaiber]

^ I just read you used a "Used" MC. Next step is to replace that with a known working one, also known as NEW.

[kingston]

Yep, stoopid move on my part. For grins, I dug my old one out today and pumped actuator on it (I didn't want to say I pumped the shaft), and fluid shot out of both apertures... Wonder if that one was OK, too, and I have another problem. I do plan on getting a new one. Even if that's not the problem, at least I'll have a new MC.

And Farbin, thanks again for the response!

[payney8]

Wont be booster loosing vacuum because that creates a vacuum assisted brake pedal. If your loosing all pressure your m/c is broken or you've got a leak somewhere loosing pressure/ sucking in air. Your saying your reservoir doesn't move when you pump. So check that your rod is actually travelling onto the m/c and its adjusted correctly. So you know your foots moving the pedal properly. Then change the cylinder with a new one as farbin said before or a known working one of somebody else's car. Also it will work with no pressure in it, as there isn't anything stopping the fluids movement therefore there is no restriction to flow. No pressure = no pressure on seals = looks to work.

[kingston]

Wont be booster loosing vacuum because that creates a vacuum assisted brake pedal. If your loosing all pressure your m/c is broken or you've got a leak somewhere loosing pressure/ sucking in air. Your saying your reservoir doesn't move when you pump. So check that your rod is actually travelling onto the m/c and its adjusted correctly. So you know your foots moving the pedal properly. Then change the cylinder with a new one as farbin said before or a known working one of somebody else's car. Also it will work with no pressure in it, as there isn't anything stopping the fluids movement therefore there is no restriction to flow. No pressure = no pressure on seals = looks to work.

Hmm...OK, so there could be an internal problem with the brake booster that would cause the MC to not be actuated? Interesting! I searched and did find someone who said that there booster was broken, and wasn't moving the rod, and basically fel apart when they removed it! Thanks also for the additional info on the MC. I figured that might be the case; with no resistance, the MC might pump fluid and appear to work.

I've got a used booster coming my way, so I'll try swapping that out as well.

Thanks again!!

[payney8]

Yes, most things hydraulic will appear to work when under no pressure. Most shops will create a pressure to test the cylinder is sealing correctly. Going of what you have said seeing as the brake fluid doesn't drop after some pumping. It would seem to be that the mc is bypassing fluid not allowing pressure to rise.

[kingston]

Yes, most things hydraulic will appear to work when under no pressure. Most shops will create a pressure to test the cylinder is sealing correctly. Going of what you have said seeing as the brake fluid doesn't drop after some pumping. It would seem to be that the mc is bypassing fluid not allowing pressure to rise.

Thanks for the response! It does seem that I've got 2 problems. Firstly, a probable bad MC. Second, an ABS issue. I'm going to order a new MC from Pelicanparts when I get paid on Friday. Man, I hope that does it!

Thanks guys!

[payney8]

With the abs issue. Check your pulse wheels for dirt. Because they can clog up and not allow the system to read wheel speed. Also check your fuses/relays

[kingston]

With the abs issue. Check your pulse wheels for dirt. Because they can clog up and not allow the system to read wheel speed. Also check your fuses/relays

I'll check the pulse wheels. I've replaced all the fuses with new ones. I'll be checking the relay under the dash tonight when I get home from work.

Thanks Payney8!