73 240z rear drums won't bleed.

[busted240]

So a while back a piece of the wheel cylinder failed and broke off inside the drum damaging everything during a short drive. Now, I replaced the drum(scoring), wheel cylinder(broken and leaking fluid), hard lines(nut stripped) and brake shoes.

After endlessly bleeding the brakes with my brother helping, I still can not get them to bleed. The front are fine, perfect in fact, but the rear is like it has air no matter how much I bleed it. When pressing the pedal while driving I usually have to pump 2 or 3 times before it catches and it normally just goes to the floor with the brake light in the dash coming on if I don't pump it. The car stops fine after that, but feels like the rear is not working.

Is there something I am missing? I am bleeding from passenger rear to driver rear and while doing so the fluid just comes out dripping not the normal solid gush that it use to.

Any help or tips would be appreciated greatly.

[Zed Head]

Are you sure the fronts are good? How can you tell that they're perfect if the pedal goes to the floor? Did you do any work on them while you were working on the backs?

The rear brakes can be weak for a while until the shoes get seated in the drums. You might have weak back brakes because they're new, with air in the front calipers causing the pump-up problem.

[busted240]

When I bleed all four corners, fluid comes out the fronts in a steady stream like they should, while the backs only barley run out like a slow drip. That is what I was referring to since I can not tell with the peddle issue. Front brakes were not touched other then bleeding them to check for air in the lines.

While they are "seating" would this cause there to be little fluid coming out during the bleeding process?

Edited November 15, 2011 by busted240

[AxtellZ]

bleed the master for the rears first, then rebleed at the back.

[Captain Obvious]

While they are "seating" would this cause there to be little fluid coming out during the bleeding process?

No.

I'm with AxtellZ. Sounds like a master cylinder issue. Sounds like it needs to be primed. That, or it coincidently failed at the same time as your rear cylinder.

[Zed Head]

Good points about the master cylinder. Did the fluid level ever drop to the bottom of the reservoir during bleeding? That could have introduced a bubble in the master cylinder. You have to keep the fluid level off the bottom of the reservoir during the whole process, once you start.

Also, apparently, the master cylinder seals can be damaged by the bleeding process if they run over crud at the bottom of the bore. But if they pump up, it's more likely air n the system.

The brake light in the dash turns on because of the pressure imbalance between front and back. It's a warning light that something's wrong. Pumping the brakes balances the pressure.

Good luck, brakes can be time-consuming to get right.

[busted240]

bleed the master for the rears first, then rebleed at the back.

I'll give that a shot tomorrow.

Good points about the master cylinder. Did the fluid level ever drop to the bottom of the reservoir during bleeding? That could have introduced a bubble in the master cylinder. You have to keep the fluid level off the bottom of the reservoir during the whole process, once you start.

Also, apparently, the master cylinder seals can be damaged by the bleeding process if they run over crud at the bottom of the bore. But if they pump up, it's more likely air n the system.

The brake light in the dash turns on because of the pressure imbalance between front and back. It's a warning light that something's wrong. Pumping the brakes balances the pressure.

Good luck, brakes can be time-consuming to get right.

The bowl never went dry, other then when everything was off and the lines were being replaced. I don't think there was any gunk or crud in the lines, they were fully drained and filled with new fluid while the brake lines were being replaced. Hopefully bleeding the master will solve the problem, I never had to bleed the master before, even when I first got the car and there was no fluid in the lines at all. Maybe that was just lucky, I'll find out tomorrow.

Thanks guys.

[beermanpete]

Also, make sure the brake shoes are adjusted to be close to the drums. You should be able to detect a little drag here and there as you turn the drums by hand. If they are too loose it will cause a low pedal.

[busted240]

Bleed both front and rear at the master and then at the brakes. Solid flow like it should but still have to pump the brakes once to get them solid.

Also, make sure the brake shoes are adjusted to be close to the drums. You should be able to detect a little drag here and there as you turn the drums by hand. If they are too loose it will cause a low pedal.

I adjusted the wheel cylinders out as far as I could and it still has no drag on either side. Am I missing something? These are brand new pads with only a few miles on them. Oh, and in case it matters the emergency brake has not worked since the wheel cylinder failed. It is hooked up properly and the cable works but it does not stop the car at all, assuming this is hand in hand with the rears not working. Edited November 16, 2011 by busted240

[olzed]

Silly question, but are you turning the adjuster for the rear brakes the right way. If its all the way out you should not be able to turn the drum. Just another thought, perhaps the brake shoes are not the correct ones. Do they look to be the same diameter as the origionals. Another thought. Can you mesure the ID of the replacement brake drum. It may be way oversize, or it may be cracked. It could then expand as you applied the brakes.

[busted240]

Silly question, but are you turning the adjuster for the rear brakes the right way. If its all the way out you should not be able to turn the drum. Just another thought, perhaps the brake shoes are not the correct ones. Do they look to be the same diameter as the origionals. Another thought. Can you mesure the ID of the replacement brake drum. It may be way oversize, or it may be cracked. It could then expand as you applied the brakes.

Yes, the adjuster is pushing the shoes outward towards the drum. The brake shoes are from MSA and match the removed ones identically. I did not measure the replacement drum but I got it from a buddy who parts out z cars, and it seemed to match my original one and has no cracks what so ever, looks very clean in fact.

How far out does the adjuster go? I turned them until it felt very hard and stopped, but it did not seem to rub the drum at all still. I was afraid to go any further and risk breaking the wheel cylinder again.

Edited November 16, 2011 by busted240

[Captain Obvious]

You should be able to lock up the rear drums with the adjuster, and the adjuster wheel should not be difficult to turn until that happens.

It's been a while since I've been in that deep into the pre-77 brakes, but I believe if you keep turning, and turning, and turning... And if by some weird set of improper circumstances occurs the shoes don't contact the drums... You'll eventually wind the adjuster stalk completely out of the cylinder. I don't remember any stops on that thing anywhere.

You know that the two sides adjusters rotate opposite directions, right? "Bottom to top" should tighten the shoes.

Can you hear the adjuster lever clicking over the teeth in the wheel as you turn it?