Another Spongy Brake Thread

[n8marx]

I need some help from the brake experts out there.

Here's the story. 1986 Carrera, stock brake system. The brake system functioned very well but due to torn dust seals on my calipers I opted to rebuild all 4 calipers. While sitting disassembled gravity drained the system for me. I also replaced all 4 rotors and put on stainless steel lines. I bled the brakes using ATE Blue fluid. I also eliminated the gap between the pistons and the pad by tapping the pads in. After initially bleeding I had a VERY firm pedal. Yesterday I started the car to back it out of the garage and the pedal sank easily to the floor with some resistance. Pumping the pedal will bring back the pressure. No leaks were found so I'm assuming air is in the system.

What is going on? How would air show up in the system because the car was running? Does this seem to point to there being air in the mastercylinder? If so how do I bleed that? Help!!

[tryan]

if you have to pump it up, it sounds like master cylinder time.

[AirCooledExcellence]

1. Bleed them again
2. If pedal hard then goto 4
3. Goto 1
4. Success!

Cheers!

[marcesq]

NX:

Any time you rebuild a caliper, IMHO, you should bleed the system first, then remove pads from one caliper at a time and insert a piece of wood (or other object plyers work too) about 1/2 the thickness of the new pad on each side of the rotor and have someone gently apply pressure until the pistons clamp the wood.

This allows the piston to move through the o-ring and boot over a greater range of travel.

After this is done rebleed and while bleeding each caliper, hit caliper with rubber mallet firmly to jar any bubbles that might be in there hiding.

A power bleeder works wonders.

Hope this helps.

[n8marx]

Any other opinions? Is this really just a bleeding issue? It felt good at one point.

[marcesq]

One thing I forgot about. Your car has an apportioning valve. It is my understanding that you really have to put pressure through that valve when bleeding.

If you still have a problem after bleeding and there are no leaks, and your fluid level is staying at the same point in the reservior, then the Master could be the problem.

[beepbeep]

also, completly new pads and discs will feel spongy for a while until everything beds in...

[North Coast Cab]

I just did the same thing on my '84. Rebuild the calipers and installed s.s. lines. I had a hard line that was damaged but once replace I still can't get a firm pedal. It brakes ok but travel on the first pump is definitely farther than on the second. I've been through 2 1/2 qts of fluid with the power bleeder.

JG