My brake light stays on and the brake pedal gets "squishy." There are no leaks anywhere to be found and the fluid in the master cylinder doesn't decrease even after a lot of driving.

I've bled the brakes (not full bleeds though) a couple of times but it keeps happening.

Could the master cylinder be putting air bubbles into the brake lines? I am stumped on this one.

Any help would be greatly appreciated.

Matt

 

Well, hopefully it's not something so simply as the parking brake dragging...

The brake light is triggered by a sufficient pressure differential between the front and the rear braking systems. If you have enough air in the system, it could trigger it, but you'd have to have a LOT of air. I would think you'd have seen it when bleeding the brakes. Other than that, a defective master cylinder or proportioning valve is about all I could think that would cause it.

 

I had a similar experience in my 1975 T/A. The MC was bad. The rubber seal in it was letting fluid back into the MC reservoir as near as I can tell... There was no air leak, just not building pressure.

It is pretty common on older cars. Remember the general rule about the life of rubber, seven years.

 

I've got a new master cyl that I'll put in this weekend. The other things I've heard is that it could be rotor runout. I hope it's just the MC! Otherwise I'll be laying down cash for a new, hopefully 1, rotor.

Matt

 

If the brakes will pump up, and give you a nice firm pedal, then I would suspect rotor runout, or, perhaps, the rears are out of adjustment.

If not, it is possible that the PV has "shut off" your rear brakes, due to some failure in the system. Do you get fluid out the rear bleeders when you bleed them?

 

Yep. I get fluid out of the rears. I was afraid of rotor runout. And I think that's was causing the problem too.

Matt

 

Also, what shape are your brake hoses in? I doubt it's the cause of your problem but it may be adding to it. Old rubber hoses like to expand when you step on the brakes, giving you a soft pedal.

Since you're doing the MC, you might want to consider changing all the hoses too while you'e at it. You gotta bleed the brakes anyway. Flush the system and fill it with fresh fluid.

 

My brakes on my 88 IROC are terrible. The pedal feels mushy. My 87 Caprice stops faster. I've replaced the pads, rear shoes and master cylinder - I really thought it was the master. Eveything bleeds correctly - I was beginning to think it was a design flaw and have been contemplating a Baer setup.

I never thought about the brake lines - they look fine. No leaks, clean fluid, etc., etc..

 

Might wanna try the brake lines. The pedal could be squishy because the lines may have some blockage in them, causing late reaction in the pedal.