Persistent low brake pressure

[Fox2506]

Again, I just rebuilt the calipers.

I rebuilt the rears first, and since I ran out of time to do the front, I went ahead and bled the rears. I went for an easy test drive and the pedal nearly went to the floor, but still had brake power.

When I finally rebuilt the rest of the calipers, I went around and bled all four AND the master. This helped bring the pedal up some, but it is still too weak.

There seems to be no fluid leaking, and the steering wheel does not pull, so my best guess is that there is air in the rear? I bled more times than I can count.

Thanks for any insight.

[stevedmc]

Do you hear any hissing noises when you hit the brake pedal?

[DMCMW Dave]

This will probably sound wierd - but drive it more. Get the brakes hot a few times and bleed again. It might take as much as 50 miles of driving for the seals to take a set.

What's happening is that the seals are over-retracting the pistons. It does not happen all the time, but often enough to notice.

You may notice that if you hit the brakes twice in quick succession the second hit will feel more normal and they will not appear to "bleed down" as you hold the pedal. (If they do, you have another problem)

[Fox2506]

No hissing that I notice. Fluid level is staying at maximum, with no visible leaks. Hitting the brake while the car is off, it feels fine and pumps up pretty hard. Hitting it multiple times while the car is on does make it feel better.

I lubed the seals before putting them in with some extra brake fluid.

The front right caliper spit out fizzy light colored brake fluid last time I bled it. When I rebuilt that one, it was the dirtiest by far. Maybe I didn't clear out the passages all the way? Besides that, however, the issue surfaced when I rebuilt the rears, not the fronts.

I feel Dave may be right.

[David T]

In my experience it is difficult to properly bleed the master cylinder of all air in the car. I bench-bleed it and then put it into the car and then bleed the front and rear systems. If the brakes do not improve take the master cylinder out and bleed it in a vise.
David Teitelbaum

[DMCMW Dave]

In my experience it is difficult to properly bleed the master cylinder of all air in the car.

Why is it different on a bench from in the car? Do you hold it at a different angle?

[Kenny_Z]

Why is it different on a bench from in the car? Do you hold it at a different angle?

I've always wondered that myself but it's traditionally been a reliable fix for many cars. It worked on my Astro when I had a spongy pedal.

[David T]

When the master cylinder is in the car it is not level, the front is a little higher. When I do it in the vise I do it so it is level. I also find it is easier to make sure it is bled because I can watch it as I pump it, you can't do that by yourself when it is in the car.
David Teitelbaum

[Henrik]

Can someone please provide a procedure for bleeding the brakes? Also, any specific tools recommended? (I read somewhere that Hervey sells a brake bleeder gadget but I am not sure if people found it useful.)

Thanks,

Henrik

[jmpdmc]

How about the link in this thread: http://dmctalk.org/showthread.php?2596-How-to-Front-Brake-Calipers-amp-Bleeding ?
I have not used it but it might help.


Jeff

[DMCMW Dave]

http://www.jegs.com/i/Motive+Products/715/0100/10002/-1?CAWELAID=1710608568&catargetid=1784156468&&cagpspn=pla&gclid=CMTooOGq67UCFc5AMgod42YAbQ


It's a good tool and commonly available.

[Henrik]

How about the link in this thread: http://dmctalk.org/showthread.php?2596-How-to-Front-Brake-Calipers-amp-Bleeding ?
I have not used it but it might help.


Jeff

Super! Thanks!!

[David T]

Try this link
http://www.powersportsplace.com/parts/psl-2002?gclid=CMb85v3467UCFZOe4Aod4kcA8Q
It is pricey but it is a professional unit. They also make them less expensive in plastic. You can goggle phoenix brake bleeder. If you are into the cheapest then just buy a "One Man Bleeder" in an auto parts store. It is just 2 pieces of tubing with a check valve. Even with that it is faster and easier if you have an assistant too. Just be careful not to let the reservoir get low enough to pull in air or you have to start all over again.
David Teitelbaum