Proper brake procedure ? MC seals damaged?

[Joseph]

:blink: I have a important question about the proper way to depress a brake caliper when taking it off for breakpad replacement. I was working on my girlfriends 2003 chevy malibu (Fronts are disk, back are drum) I had to push the calipers back in order to clear the brake pads to get it off. I took a C clamp and slowly moved the pistons back and did the break job. After I was done with the break job I had a spongy pedal. Before the break job It was pretty firm.

Did I damage the master cylinder seals by not opening the bleeder screw before depressing the piston in the calipers?

I have bleed these breaks quite a bit afterwards and checked all hardware. Everything is working fine except the spongy pedal. Travel is about 1/2 way before they grip or a bit more. Adjusted back drums with no effect.

Is it a given that you will damage the master cylinder seals by not opening the caliper bleeder before pushing the piston back ???

I installed a new master cylinder on this car just last year.
Thank you.

Topic

[Joseph]

Finally figured it out. Ok, I did not loosen the bleed valves in the front brakes. I just pushed them in like an idiot. I think I might have caused a problem with the Master Cylinder as it is soft now. So, Any way out of this without buying a new one or should I just suffer the lesson learned and buy one?

I was thinking of blocking off the brake lines and testing it before I rush out to buy another.

I appreciate any advice, I screwed up I guess.

[Andrew Harris]

I pushed brake pistons back in for years without opening the bleeder screws. Anyway not saying you should do that however I have never damaged a master cylinder to my knowledge by doing this. not saying it cant happen but it would be a rare thing. Did you open the system up for anything or all you did was a pad swap.

[Joseph]

All I did was take the caliper off as the disk(s)are in good shape. I wanted to replace just the pads and regrease the pins. So, I could not get the calipers off of the front end without compressing the pistons back. So, I used a screw driver to force them back a bit and a C clamp to compress them back for the new pads. I replaced the pads and then after that the pedal was spongy.

I have been thinking about this all day and my thought is – IF i did damage the MC by compressing the caliper pistons then who could that happen? Obviously the seals should take that type of pressure because its not even as much as when you apply the brakes from the pedal.

Eventually, I took it over to my neighbor – who has a full shop I envy alot – and we actually replaced the front calipers. Same thing. So, we bleed the fronts quite a bit. No change. No air.

I really do not understand this.

[Joseph]

I would like to also say that this car has NO ABS in it. That is how it was ordered back in 03. What is pretty wierd is that there is a 50amp fuse installed in the fuse box for the ABS. So, I think a closer look is warranted on this situation. Perhaps they left the hardware in and just somehow disconnected the abs? Hard to tell sitting from a keyboard.

I am also thinking that what I will do today is block off one of the circuits for the breaks at the MC and check the firmness of the pedal. Perhaps block off all of them and see if the MC has good pressure to start with.

The one thought I have on the back burner so to speak is that because she wanted no ABS breaks, The module for ABS is still there but disconnected electrically somehow. Its possible that air in the module would cause this. But thats a small thought as I certainly would think they would do that. But you never know.

I will eventually find the problem and will report it back here.

Thanks for your reply.

[Dave Tidman]

How is the adjustment on the rear drums? A lot of your pedal feel is dictated by the rear brakes. I would try adjusting the rears and see if the pedal feel comes back.

Also, if you have not tried Eric’s method of resetting the master you may want to give it a try. His method is to get in a safe space whey you can accelerate to a good speed and then stand on the brakes. Do that 3 or 4 times and see if the pedal feel comes back

[Alexander B]

Bleed the rear brakes too? if you had the calipers off, you probably have a tiny air bubble somewhere, which would explain the slight sponginess..

[Brian]

There are a few important topics I want to go over. When you installed the new master cylinder, did you bleed it before hooking it up?
Yes, there could be air in the abs module.

If I were.in your shoes, ide say forget bleeding the brakes and replacing parts.
Do a full brake system fluid flush. Not bleeding, but flushing. There are.procedures to follow for this and they are easily found on yt.
Brake fluid is supposed to be clear, buy when it’s not transparent, that means it’s contaminated with moisture and it’s rusting the steel lines from the inside out. Because you changed the MC out a year ago, the resivior fluid will likely look good. It will cost you one whole quart of brake fluid and about two hours.
This is one of the most seriously overlooked things on a braking system.

[Author]

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