87L6

I’ve been having problems with the brakes on my 87 F150. I’ve replaced the master cylinder, both calipers, rear wheel cylinders, and the rear ABS valve. Changing the rear ABS valve fixed one of my main two problems. I believe the old valve was frozen the off position. Now I can tell that the rear brakes are 100%better. But I still have a major problem on the front brakes.

The best way I can describe the problem is, it feels like there is something acting like a wedge prevent the calipers from moving as I hit the brakes. Like putting a 2x4 in a sliding glass door to prevent it from sliding.

It does not happen all the time, but when it does boy howdy it’s bad. Yesterday I was going too fast to pull into a parking lot. When I hit the brakes harder than normal, I had no front brakes what so ever. Tried pumping the brakes, but only the rears operated. I also pressed as a hard as I could, again only the rear brakes locked up. No front brakes at all.

I thought there might be a problem with one of the new calipers, the right side wasn’t freewheeling as the left. Maybe it was a frozen, so I replaced it 3 months ago. But after yesterday, I know I still have a major problem somewhere.

I inspected the fronts today. They all look normal. No foreign objects. Nothing is binding. The pistons moved easily back into the calipers. After pressing the pistons in, the calipers slid back and forth normally on the pins.

It’s not the vacuum boast. It is working properly and the pedal moves normally. I don’t have to press hard to get the brakes to operate. BTW, I bled the brakes after each part changed, and the pedal is not spongy.

My gut feeling...something is restricting fluid to the front brakes. Not at all times, a constant problem would be easier to find, but intermittent. I notice that this truck doesn’t have a combo metering/proportioning valve. I got some large thing (metering I think) attached to the master cylinder line. Is there a way to test it?

I’m not sure what the problem is and looking for help to point me in the right direction. Thanks in advanced!

Tfraser

Hey! SI I'm new to the f150 trucks but have you changed the rubber brake hoses as well? And my suggestion would be to trace along the metal brake lines and see if there is a pinch in a line. I'm pretty sure brake lines aren't supposed to be kinked or have an agressive bend to them. If it's none of those I might think that you have something plugging one of the lines maybe.
And the last thing I can think of doing is bleeding the brakes again just to make sure you have a clean even spray coming out of the calipers.
That's my thoughts. Hopefully someone else comments as well. Hope this helps a little. Keep me posted!

87L6

Thanks for your reply. Yes I replaced all of them withsteel braided hoses. Here’s an update of what I did:

I took apart the entire front hydraulics system and blew out the lines. I can’t say that I saw anything that came out other than brake fluid.

I replace the drive’s rear wheel cylinder. The bleeder screw was frozen shut and I couldn’t bleed it. An auto shop cranked it down too hard when I had thembleed the brakes the last time. When checking the passenger’s side, I found thewheel cylinder was leaking. So I replaced it too. But I’m afraid the shoes gotsaturated with fluid.

I cleaned everything, bleed all points again, and adjusted the rear brakes. They feel much better now, but I was too tired get new shoes to put on. I’ll replace them in the future.

Chris_1

iTrader: (1)

That new master cylinder could be faulty. Not supposed to happen with brand new parts, but it does on occasion.