Brake bleeding issues

[Devin]

I installed new calipers on the rear (with old lines) and installed the old calipers on the front (cleaned) with new lines. The fronts have been open for a few years and the rears have not been. Anyway, I dumped most of one of the big cans of brake fluid in the master cylinder and started bleeding the right rear caliper. I have no power but I was able to get all of the air out eventually.

The problem started when I moved on to the driver side rear. No matter how much we pumped we couldn't get the fluid to come out. I eventually took off the banjo bolt and had my friend pump the brakes, and the fluid came dribbling out.

I didn't take the bolt off this time, but the front passenger side wouldn't bleed either. Am I missing something?

 

[gmorrell]

Is the rear suspension hanging free? If so the rear bias valve is limiting flow to the calipers. Support the rear so the suspension is compressed at normal ride height, or clamp on the lever on the bias valve so it thinks the suspension is compressed.

Gary M.

 

[Devin]

I haven't touched the suspension in the rear. All I did was replace all of the brake hardware. The brakes are all bolted on and in place.

Also, when I press the e-brake the rotors still rotate, but the spring is compressed by the cable.

My friend's father suggested that we may need to bench bleed the master cylinder, but I'm unsure what that means, especially when ABS is involved.

 

[gmorrell]

Let me re-phrase the question(s).

1. Rear wheels are off?
2. Is the rear of the car sitting on jackstands to the body?
3. Is the rear suspension hanging free at full droop?

Reason I ask these; all Tauri have a rear brake bias valve that is connected to the forward lateral link on the driver's side. This valve sets the rear brake bias (line pressure) based on the compression of the rear suspension: More compression = more rear brake pressure, less compression = less rear brake pressure.

If the rear suspension is hanging free, as in if the answers to questions 2 and 3 are true, then the bias valve is at its lowest line pressure setting, and will almost completely shut off fluid flow to the rear calipers, making brake bleeding difficult to impossible.

Also, when I press the e-brake the rotors still rotate, but the spring is compressed by the cable.

This is because the E-brake adjustment has not occured yet. Technically, what you should do here is turn the caliper pistons counter-clockwise a bit until the extra space is taken up between the pad and rotor surfaces. You want to just get them touching, but not so much that the brakes drag with the E-brake off. This adjustment is done with the E-brake OFF.

It isn't totally necessary to do this, as the self-adjustment process will commence once line pressure seats the pads to the rotors, but pre-setting the calipers pistons speeds up the process a bit.

Gary M.

 

[Devin]

Gary, thanks for your help.

The car was up until yesterday, but it is now sitting on it's tires. I started the bleeding process after we lowered the car onto it's own weight.

 

[Devin]

Any other ideas on my bleeding problems? I'm going to take another crack at it tomorrow.

1. So I should be able to bleed the brakes with no vacuum assistance, right? This is assuming that the brake booster is vacuum assisted...

2. With that in mind for the rear brake, if I stand on the brake pedal, should the fluid come dribbling out or would it spray? Right now I can push the brake pedal to the floor with not a lot of effort.

3. Does ABS complicate this? The ABS computer is attached to the wiring harness, but not all the harness tailings are connected, among other things.

 

[Devin]

Well, I'm going up there tonight to get them bled. Hopefully I'll be successful. Either way I'll report back my progress.