'77 124 Brake pedal travels about 1/2 way

[Rupesy]

I have just replaced the master cylinder, all lines, front brake calipers and pads, and rear pads (rear calipers seemed to be OK). Bled them like crazy so I am very sure there is no air. I now have to press about half way down before the brakes engage. They are definitely not soft and the car does stop right away (I can lock them up), but the travel seems too much. I am wondering if it has something to do with the rear brake calipers as it looks like they are supposed to automatically adjust (based on the fact that I had to screw them back in to change the pads). Does it take a while for them to self adjust? I haven't got the e-brake totally adjusted yet and was wondering if that has something to do with it as well. I have had the long travel before on other cars where the caliper had locked up and the piston had to travel too far before making pressure.

Thanks.

[SLOSpider]

Rear should self adjsut. Did you start by bleeding the air at the lines right off the master? I always start there. Helps to have a pumper but a piece of wood helps with me as no one is usually around. After all the air is bleed there then I start at the right rear, left rear, right front, left front.

[narfire]

Noticed you changed the master Cylinder. I'd like to think it would be the same as other MC's, but in my case the things all seem to have needed adjustment of the "acorn" nut on the booster plunger. This winter swapped booster and same thing, had to adjust the acorn nut for the brakes to work properly.
perhaps the acorn nut is not pushing the plunger? in the MC in far enough?
http://www.international-auto.com/fiat- ... lation.cfm
You get good at removing the 13 mm nuts, half turn out of the acorn nut replace and try drive/brakes....repeat if required... (I had to about 6 times...)

[Rupesy]

OK, so I pulled off the mc and just adjusted the nut out a little. I didn't follow the instructions, just eyed it a little. Put the mc back on and tried the brakes while the car was not running. At this time, the brakes felt perfect to me. I just rolled it back and forth a little to make sure things were not hung up by over adjustment. Thought I was done.....and then I started the car and the brakes sank to 1/2 way again! So I took the mc off again and measured it this time. I think I got it correct, but the same thing happens. When the car is off, the brakes are high and then the pedal falls about 1/2 way when I start it.

Another interesting thing is that I cannot get the ebrake adjusted correctly. No matter how hard I tighten up the nut on the bottom of the car, I can not get the car to stop when I pull up. When I do tighen it, the rear brakes drag hard. When I loosen it to let the rear brakes free, It doesn't really work again. So I am stumped. I will say I have replaced all brake lines, all brakes, the mc, and only the front calipers. I did not change the rear calipers as I thought they seemed to work fine. I can see the rear rotors are polished so I know they are grabbing. Should I replace the rear calipers??

Anyway, hopefully some of these things I mention will lead to some clue of what is going on. Once again, brakes are NOT spongy. They grab very good.

[Rupesy]

Update,

I pulled the rear calipers and found that there was a big gap between the piston and pad. I knew this was there before, but figured that the automatic adjustment would take care of it. I had turned the piston all the way in and I think you are supposed to back it out a little to get it started on the threads. Well I also found a little locating button on the back side of the pad I had not noticed before that was causing a problem for the pad to sit flat on the piston. Ground that off and adjusted the piston out until the pads fit just barely over the rotor. This helped with the hand brake which works better, but still isn't as good as I would like. However, this did not correct the problem so I went back to the acorn nut. (But I feel much better about the rears)

Turns out that the way I adjusted the acorn nut I was just spinning it round and round. So I decided to pull it out to see how it works. Ahhhhh! Now I see. So I ended up adjusting the acorn nut out 4mm to get the feel of the pedal I was looking for.

Thanks for the help and patience!

[narfire]

Careful in having the acorn set out too far. The acorn could then be pushing against the MC when the two MC mounting nuts are tight and the front brakes could then be partially engaged. You'll find out after a 5-10K drive as the pads will heat up and drag/smell.

If you put a straight edge on the face of the booster, the acorn should be proud of the face about 1 mm or so.
http://www.international-auto.com/fiat- ... lation.cfm

[Rupesy]

Posting a followup as initially I though I had this pegged. For a few days, brakes worked fine without any issue. Then one day the rear brakes started to slowly lock up. Originally I thought someone had left the handbrake on and that was what caused the problem. I showed up an hour later and nothing seemed wrong. Drove the car home without any issues. A few days later it happened again. After waiting a half hour or so, it was possible to drive home. So this is Texas summer and it almost seems like the problem only happens in the late afternoon when its around 100F or so. Never happens in the mornings or late at night. I know that sounds crazy, but outside the hot afternoon there is never an issue. I know it is a rear brake issue because the rear rims have black soot on them and the fronts do not (just the opposite of a car with working brakes). I have bled all the brakes over and over again and I do not have spongy brakes. The car does dive slightly when I hit the brakes, but no soot on the front rims. I will say that when the brakes change condition (start to lock up), the brake pedal becomes very firm (almost like I should be able to adjust the acorn nut back and have a properly working system). This has plagued me, because I do feel like I had to adjust the acorn nut way too far. It is almost like I have compensated for something not working in the system. Maybe once in a while something in the system corrects itself and then the acorn is adjusted too far. The car is lowered so I don't know if that has something to do with it. I checked out the compensator lever, but don't really know how much travel the arm undergoes during normal operation. It doesn't seem to move much. When I hold the bar all the way down (simulating hard braking) the rear brakes still work. I am not sure if the compensator is supposed to limit the pressure or completely shut it off. Once again, after it happens we just wait about 1/2 hour and it is driveable again. Seems like pressure is building under certain circumstances and not able to bleed off quickly so the rears heat up. Another way of looking at this is that maybe there is something like a check valve that is supposed to hold pressure in the rears and is not working so I have had to compensate by adjusting the acorn nut too far. One other thing to mention is that if I go to the car right now, the rear calipers are not tight or dragging the rear rotors. They seem normal to me and the rotors rotate freely so I don't think I have an ebrake adjusted too tight or a situation where the calipers are already tight or dragging. Anyway, not sure what to try next except replacing rear calipers and compensator. Any suggestions welcome.

[majicwrench]

YOu have the rod into the MC too tight, back it off.
That little tab on the back of the brake pad is THERE FOR A REASON get new pads, align the tap with the groove in the caliper piston.
KEITH

[Rupesy]

Turned the acorn nut back in 3mm (originally turned it out 4mm) and brakes are working fine now. It travels a little far for my taste, but not bad. Pedal is firm and I can lock up the tires so I know we are clear of air. Now on to something else.....

[joelittel]

How did you adjust the acorn nut without turning the entire plunger shaft?