Squishy first press on the brake pedal then solid.

[Itjustruns]

Hey there. Have a 94 mustang GT I have been smashing away at, got it dirt cheap and have done more work than I care to admit to the car getting it road ready. I have ran into a weird situation. When I bought the car the previous owner said the brake pedal was soft on the first press then great after that, usually as if there is air in the system and the car had an abs light. He also said the master cylinder was replaced recently. Well I hooked it up to a scanner and it threw a voltage code for the ABS pump verified fuses and wiring and tested the pump, it was bad. I didn't want abs anyways so I bought a delete block from PRB. Installed it, bled the brakes and the master cylinder (not on the bench, the old rags and twisting method) and to my surprise, the pedal did the same thing as before. First press or two is squishy then it is great.

I thought I was an idiot and missed a leak or bled it poorly. Noticed the lines from the master were rusty, replaced them with high quality copper lines. Then proceeded to bleed then check the lines throughout the WHOLE entire brake system front to back. No leaks. Had a person pumping like crazy the whole time I searched (the better part of an hour)

So I rebled the brakes and master cylinder not once, not twice, but 5 times now and it's not getting better. I have cycled a GALLONS worth of brake fluid. If there is air in the system I am absolutely dumbfounded where it is getting in and there is NO leaks. I noticed there is a squishy noise coming from the master, sounds like air, but I have bled the thing 5 times, albeit not bench bled, but even if not perfect the symptom should have gotten a little better I would think, and I have never had an issue bleeding this way before. I also noticed the front brakes have amazing pressure, constant stream, but the rears shoot a stream for about half a second then just drip off the caliper in a steady line. I am running out of ideas other than the master being bad but it's a newer unit. Any help would be appreciated. Thanks.

 

[Bustedknuckle]

My grandson's tauras had weird brake problems an intermittent abs light, hard pedal, too much pedal travel.. It was the vacuum assist. The only way I finally figured it out was it the vacuum assist just quit.
I replaced it, gawd awful job, and it took care of everything the brakes had wrong with them. No ABS light since.
There are only 2 parts you haven't went through. Vacuum assist, proportioning valve. You said the back brakes bleed different. I don't know how to check that, but I would fi d out how or replace it with an adjustable valve. ...just in case it ain't the problem and it looks planned.

 

[stormsedge]

Hey there. Have a 94 mustang GT I have been smashing away at, got it dirt cheap and have done more work than I care to admit to the car getting it road ready. I have ran into a weird situation. When I bought the car the previous owner said the brake pedal was soft on the first press then great after that, usually as if there is air in the system and the car had an abs light. He also said the master cylinder was replaced recently. Well I hooked it up to a scanner and it threw a voltage code for the ABS pump verified fuses and wiring and tested the pump, it was bad. I didn't want abs anyways so I bought a delete block from PRB. Installed it, bled the brakes and the master cylinder (not on the bench, the old rags and twisting method) and to my surprise, the pedal did the same thing as before. First press or two is squishy then it is great.

I thought I was an idiot and missed a leak or bled it poorly. Noticed the lines from the master were rusty, replaced them with high quality copper lines. Then proceeded to bleed then check the lines throughout the WHOLE entire brake system front to back. No leaks. Had a person pumping like crazy the whole time I searched (the better part of an hour)

So I rebled the brakes and master cylinder not once, not twice, but 5 times now and it's not getting better. I have cycled a GALLONS worth of brake fluid. If there is air in the system I am absolutely dumbfounded where it is getting in and there is NO leaks. I noticed there is a squishy noise coming from the master, sounds like air, but I have bled the thing 5 times, albeit not bench bled, but even if not perfect the symptom should have gotten a little better I would think, and I have never had an issue bleeding this way before. I also noticed the front brakes have amazing pressure, constant stream, but the rears shoot a stream for about half a second then just drip off the caliper in a steady line. I am running out of ideas other than the master being bad but it's a newer unit. Any help would be appreciated. Thanks.

Any odd twist or high point in the brake lines could retain some air, even with all the bleeding you've done. Look it over closely for any spot that might harbor air and see if you can bend the tubing a bit differently so it will pass. Note: I had one motorcycle that required the brake calipers to be pulled from the mounts and turned in order to get the bleeder screw high enough to pass the air. Beyond that, I'd suspect the power booster as previously mentioned...or, that the new master cylinder you have was actually rebuilt and done so incorrectly.

 

[Mustang5L5]

I had this same issue on an infiniti I owned. I got used to double pumping the brake to firm it up.

Thought it was air and put gallons of brake fluid through the system, but it ended up being a bad rear caliper. The slide pins on the caliper were seized so the caliper didn’t really float properly. I replaced the caliper, and the problem never returned.

 

[General karthief]

You mentioned twice (or maybe tree times?) that the master cylinder was not bench blead, you need to do this, most master cylinders are mounted at an angle and the air bubble will be trapped and not move. Then you need to replace the hose going to the rear axel, they get old and swell on the inside, if there are hoses to each rear caliper change them too.
Oh, and copper lines are NOT to be used for brake lines, replace them with steel lines.

 

[revhead347]

I can say with almost certainty that he didn't bench bleed the master cylinder before installing it. Common mistake. You can pull the master cylinder and bench bleed it, or just get a Motive Products pressure bleeder. Trust me, it's worth the money. Hook it up, pump it up and crack all 4 bleeders at once. That thing gets air out of any place.

Kurt

 

[Itjustruns]

Alright so as an update, I properly bench bled the master and there was no difference. I'm thinking it was a defective rebuilt master that was junk on arrival. I have just about checked every line, caliper and hose about 10 times. A lot of the symptoms make sense for a master cylinder failure as well, all 4 calipers work smooth as butter, none of the rubber hoses swell and they look in great condition, no leaks anywhere on the system, checked the booster and there isn't any fluid leaking back into it and it's working great like it's supposed to. I guess it was just hard for me to wrap my head around a new part being bad out of the box, Haven't really dealt with that problem before. But I guess at the end of the day all that keeps the master together is a few rubbery rings, an easy failure.

Thanks to everyone with the great suggestions, it helped a lot to check off every box on the list. I'll let y'all know if it was the master or not.

 

[revhead347]

Alright so as an update, I properly bench bled the master and there was no difference. I'm thinking it was a defective rebuilt master that was junk on arrival. I have just about checked every line, caliper and hose about 10 times. A lot of the symptoms make sense for a master cylinder failure as well, all 4 calipers work smooth as butter, none of the rubber hoses swell and they look in great condition, no leaks anywhere on the system, checked the booster and there isn't any fluid leaking back into it and it's working great like it's supposed to. I guess it was just hard for me to wrap my head around a new part being bad out of the box, Haven't really dealt with that problem before. But I guess at the end of the day all that keeps the master together is a few rubbery rings, an easy failure.

Thanks to everyone with the great suggestions, it helped a lot to check off every box on the list. I'll let y'all know if it was the master or not.

New part being bad out of the box......we call it "A1 Cardone."

Kurt