BADFNZ

iTrader: (19)

I have made several posts about this but I have finally given up

Situation: Months ago I replaced my calipers with another used F-body set and my brake lines with some Russell Stainless lines. I replaced the calipers because I was getting rid of my Pro Stars and didn't want the shaved ones anymore. My brakes had always performed flawlessly and I had a good pedal feel.

After I replaced everything, I bled, bled, and bled some more, but there were always bubbles. I found a couple of the fittings leaking, so I tightened them, bled a few more times, but still the same amount of bubbles. Nothing was changing. So I bought the Motive Power Bleeder and the thing works awesome, but still the same amount of bubbles. I'm not talking about a couple here and there, I'm talking about a good 10 seconds of bubbles per caliper, every time.

So today I took the MC off the car and bench bled it. Maybe I wasn't doing it right, but the bubbles never went away. I would push in the cylinder, a few bubbles would come out, I would release, then some of the bubbles would get sucked back up. So I'd push it in again, pinch off the line, but it didn't do any better. Every time I pushed in the cylinder, bubbles would come out. So I said "F it", maybe this is how it's supposed to be. Put it back on the car, bled from the calipers I couple more times, but still the same amount of bubbles as always. There are no visible leaks anywhere.

I am at a complete loss. I have done everything short of rolling my car off a cliff. I have gone through at least 6 quarts of fluid at this point and nothing has changed. I mean, the amount of bubbles hasn't even decreased. My pedal goes all the way to the floor, but it does hold some pressure.

So if someone can give me something, anything, and it fixes my problem, I will pay you $25 the day of. Could there be something wrong with the new calipers? Is there an easy way to spot a leak in the system if it's one of the lines or fittings? Please help!

metalmilitia606

iTrader: (8)

On my friend's rx7 he had similiar problems. It turned out to be a bad proportion valve. I don't know if you have one or not. I just read prostars and assumed you spent time at the track. It was also a bad master cylinder. So we replaced both of those and everything worked fine. Just shooting out ideas for you ha ha.

BADFNZ

iTrader: (19)

Yes, I did forget to mention I have an ABS delete and a proportioning valve. It would be one hell of a coincidence if this or the MC went out when I changed the calipers and lines.

wrencher

iTrader: (2)

Dumb question, have to ask is the bleeders on the top of the calipers?
No leaks anywhere?
Does the pedal pump up/gain height fell if the pedal is repeatily pressed?

BADFNZ

iTrader: (19)

Yes, calipers are on the correct side of the car. All bleeders are up.

No visible leaks anywhere.

Pedal does not gain any height if pressed repeatedly. The pedal goes almost completely to the floor, but it does hold enough pressure to stop the car.

metalmilitia606

iTrader: (8)

If the F-body MC is similar to the one on the FD the master cylinder should have an internal valve inside. Check and make sure the valve moves freely. If not then you should try another master cylinder. That's only if our cars have an internal valve. I am not exactly sure how our brakes are put together.

wrencher

iTrader: (2)

Get another master cylinder.

BADFNZ

iTrader: (19)

Is this just a shot in the dark suggestion or do you see a reason why this might remedy my problem? A poster on another board said it's possible to over-extend the MC if I pushed the pedal all the way to the floor which could blow seals. Ever heard of this?

metalmilitia606

iTrader: (8)

The same deal happens when people use those power vacs to bleed their clutches. The vaccuum causes the seals to blow out if it is too much. So maybe by some accident of sorts that could happen with brakes too.

BADFNZ

iTrader: (19)

True. And I am using the Motive Power Bleeder, but I've never used more than 15psi. I wonder if that would be enough to damage seals.

metalmilitia606

iTrader: (8)

See if you can swap a MC with one of your buddies and see if that helps before you lay down the dough on a new one. From what you have told us so far I think your problem is in the MC somewhere.

wrencher

iTrader: (2)

If you cannot build pressure & it wont pump up with no leaks you likely have a bad master.
Short of having a caliper or pin issues that pretty much what it sounds like.
Some master's also dont do well being bled out after years of use.
The piston extends further in the bore than ever before during bleeding.
That can cause sealing issues afterwords also.

metalmilitia606

iTrader: (8)

After a quick search our MC's look just like the one on the FD. Try this. Take off the two brake lines directly to the MC. Put your finger over one of the holes and have a friend push down your brake pedal at the same time. If your MC is good you should feel pressure coming out of the hole and against your finger. Do the test for both holes. If you have pressure on both holes then your MC should be fine. THis is what we did with my friend's car.

BADFNZ

iTrader: (19)

Well when I bled the MC, the fluid moved through the lines fine, so I know there's pressure there.

BADFNZ

iTrader: (19)

I don't know if this makes a difference, but I have a very firm pedal with the car off or in ACC, but the second the engine starts, I lose everything.

Also, I'm still hearing conflicting things on whether or not a pressure bleeder will bleed the MC. I think it does because it bleeds from the reservoir down, but some say the actual piston has to be compressed to bleed it. I don't know why this would make a difference.

ANTICOP RAM AIR

iTrader: (7)

brake booster valve???
there should be a one way check valve inline between the booster and intake... my brothers did the same thing.. replaced the valve and it fixed his problem..

BADFNZ

iTrader: (19)

That shouldn't allow air into the system though.

metalmilitia606

iTrader: (8)

If it is bad it will let air in. I wonder if a line slipped off somewhere since you said you upgraded to stainless. Even if it is still attached somewhat if it is not all the way on air could come in.

mitchntx

iTrader: (14)

Not sure what you mean by "replaced everything". What is everything and at what point did you have good brakes and then you didn't?

Define air bubbles. Tiny bubbles that look like carbonated soda or real bubbles that displace more than 1/2 the line? How loose are you loosening the bleeder screws? Loosen just enough to allow fluid to pass.

Do the "bubbles" appear to be the same on all four corners or just at the calipers you replaced?

Used calipers? You sure the bleeders are OK? How about the threads? I have seen tiny bubbles generated from a bleeder screw opened too far and air getting past the threads.

You bench bled the MC. Did it ever run dry? Bled on or off the car? See how the MC is angled up in the front when mounted on the booster? That will leave an air bubble in the very end of the cylinder. MC has to be level to bench bleed.

Line lock. You sure you have the rear most lines on the MC routed to feed the front brakes and the front most line on the MC feeding the rear brakes? Are the lines all below the level of the MC? Lines above the MC is a high point in the fluid system and can trap an air bubble.

Your Motive Power bleeder is a sucker or a pusher? If it's a pusher, back flush the system.

I didn't dig too far, but does your pedal ever get hard and stay at the same height when mashing the pedal? Does it stay firm or does it slowly go down to the floor?

Can you pump and recover pressure?

BADFNZ

iTrader: (19)

I replaced the calipers with a used set and the lines with stainless ones. I had good brakes before I replaced the calipers and lines.

Big air bubbles. When I open the bleeder screw, the first linear foot of the clear line is air, then the fluid starts (same on all 4 corners). I just loosen enough to let the fluid pass, not any more.

I replaced all 4 calipers, but yes, it's the exact same on all 4. No matter how many times I bleed, the amount or size of bubbles has not changed.

Yes, used calipers. I'm not sure the bleeders are ok but I haven't seen any small bubbles or anything around the threads when bleeding. I even took the rubber caps off so I can see around the bleeder when opening and closing them. No issues.

I don't think I ran it dry, but it's possible. That's why I went ahead and bench bled the MC. I bled it off the car and made sure it was level, not angled up. When I bench bled it, there were several smaller bubbles, but no big ones like seen at the calipers.

Yes, the LL was installed about 5 years ago so I know everything is routed properly. One thing I did notice was when doing my shock and spring install, I had to move the MC out of the way to get to the shock bolt, and in the process I bent the line going into the proportioning valve. It made a small fluid leak at the flared end into the proportioning valve, but I loosened it, seated it, and tightened it, and haven't had any issues with it since.

It's a pusher. Define "back flush".

It's firm when the car is off, but when I turn it on, it goes straight to the floor. Pumping it does nothing to change pedal height or feel. The brakes will hold enough to stop the car, but the pedal is almost to the floor to do this.

Pumping makes no change.