Okay. This should be a simple one. I have a 1987 Ford F-150. It was built in 2/87. So, in theory, it should use the 1 inch bore master cylinder. I have found the only difference between the 1 inch and the 1-1/16 inch MC is the bore. Why Ford continues to list the 1 inch MC is beyond me.

I have replaced the rear wheel cylinders, rear brake shoes, and rear drums. The rear drums were a mess and the right side wheel cylinder showed evidence of leaking. So I replaced the whole kit and kaboodle. I figured if one side was bad, the other was not far behind.

The front calipers, pads, and rotors appear to have plenty of life.

I have purchased a power bleeder that uses a pump to pressurize the MC and force the fluid through the system. After replacing the wheel cylinders, I tried my new gadget. From the rear wheel cyclinders, I continue to get very fine air bubbles out of the system. I have inspected and found no leaks anywhere, but I am suspicious. THE MC has been replaced with the "correct" 1 inch unit.

WTF? Why am I getting all these fine bubbles? The pedal goes down about halfway before the brakes are affective. I can pump the pedal once and the brakes are firm. It acts like a bleeding problem, but I can't get rid of these fine bubbles. I am considering replacing the entire brake line system with a SS brake line system and replacing both calipers, pads and rotors.

Any direction?

 

make sure you bled the abs unit the on the driver side rail on the inside . could be your problem

 

I have the same problem in my 88'. I read on this website along time ago that there is a bleeder screw on the ABS actuator mouted on the frame rail. I guess air can get stuck in this actuator and needs to be bled off. I never got around to trying this myself becasue the truck is no longer a DD and just sits in the shed waiting for me to start working on it.

 

I will check this out and give it a try. Thanks.

 

I am checking my LMC parts book and my Chilton manual. Is this unit located immediately downstream of the master cylinder?

 

it is on the inside of the frame rail on the drivers side about at the back of the fender . here is the part and what it looks like

 

Found it! Curiously, it is located next to my fuel filter. Interesting that there is no mention of having to bleed this unit in the Chilton service manual. And LMC does not show this unit at all.

I will bleed it and then the rear brakes and see if this cures my problem.

Thanks again.