Stiff brake pedal

[martin53]

Rebuilt my brake cylinders when I bought the car around 4-5 months ago. Installed a 318/904 drove it around fine with no problems. Took the family for a cruise Easter Sunday and the brakes were tight when we go home. Next day I go to drive it and the brake pedal is so stiff I can't push it down at all. The brake system is bone stock. Anyone got a idea of what it could be.

[sser2]

Binding pistons in brake cylinders?

[Don Coatney]

The fluid return port in your master cylinder may be plugged. This can happen if the pedal free play rod is out of adjustment.

 

[Dodgeb4ya]

Master Cylinder push rod has no free play? Should check that too.

Reach down to the brake pedal with your hand and see if you have  1/2" of brake pedal free play at the top.

Otherwise as already mentioned above or a swollen master cylinder piston cup or sticky piston.

If you didn't rebuild/replace the M/cyl you might want to do it.

[desoto1939]

Marting:  Did you use Dot 5, Dot 3 or Dot 4 Brake fluid.  If you used dot5 which is silicone then you would have needed to have cleaned the entire system and flushed the entire system with denatured alcohol and replace allof the rubber brake lines and rubber in the MC and brake cylinders..

 

Which type of brake fluid did you used.

 

Rich Hartung

[martin53]

Not sure on what brake fluid I used I'll see if I still have the container in the trunk. As for the master cylinder it was also rebuilt and I checked it at lunchtime and I can push it may be a 1/4 of the way down but that's it. I bleed the drivers side top cylinder and the pedal went to the floor but once I tighten the bleeder it got stiff again. The bottom cylinder barely leaked fluid. Maybe a dirty line?. Thanks for the replys.

[T120]

If by chance incompatible brake fluids might be in your brake lines,it could cause problems. It has been mentioned in the past to draw some fluid from the master cylinder and put it in a small clear glass jar - incompatible fluids will visibly separate...

Edited May 7, 2019 by T120

[desoto1939]

If you mixed non compatable fluid then the rubber cups could be swelling up so the brake pedal is hard and the cups in the wheel cylinders have sweeled and then the piston can not move.

 

Rich Hartung

[martin53]

Thanks for the reply everyone. I used dot 4 fluid on the brakes. Last night I jacked up the car, pulled the hub off to see if the cylinders were stuck. I then pushed the pedal and the cylinders worked. I had to adjust the brake pad in order to put the hub back on. I'll check the passenger side later today. 

[Don Coatney]

If you pushed the pedal with the drum removed you most likely over extended the wheel cylinders and possibly blew the seals. Your having to adjust the brake shoes in order to replace the drum is an indication that the wheel cylinders are overextended. You should never push the pedal with the drums removed.

[martin53]

6 minutes ago, Don Coatney said:

If you pushed the pedal with the drum removed you most likely over extended the wheel cylinders and possibly blew the seals. Your having to adjust the brake shoes in order to replace the drum is an indication that the wheel cylinders are overextended. You should never push the pedal with the drums removed.

When I removed the drum I barely pushed the pedal just to make sure the cylinders would move. I made sure not to push the pedal to the floor. So how could I fix the brake cylinders from over extending. 

[Jerry Roberts]

As Don said , the drum would keep the brake cylinder from over extending . And I am not trying to bother you Martin , but how could you see the wheel cylinder parts moving when you were inside the car pushing the brake pedal ? One way to see if your wheel cylinder is working is to jack up the wheel and have someone try to turn the wheel while you apply the brake . 

[kencombs]

based on the info posted, I'd place a bet on a master cylinder problem or lack of free play.  If you pump the pedal slowly but repeatedly, does the free play reduce as you pump?

 

If so that is a sure sign.