Hi,

I've got a 1989 F250 XLT 4X4. The truck had been sitting for a while before I got her. The situation is that I'm trying to resolve soft brakes that I had to pump up to stop.

I started by bleeding the brakes and found some bubbles. Also the brake fluid was pretty nasty looking (cloudy greyish, with some sediment in the front passenger caliper). I got clean fluid to run through everything, but I just couldnt seem to bleed the front brakes completely clean of bubbles. so I decided to replace the brake master cylinder. I pumped a few liters of brake fluid through the system before I gave up and decided on the new master cylinder

I bench bled the new master cylinder as specified, installed it, and proceeded to bleed the brakes in the sequence of passenger rear, driver rear, passenger front, driver front. The two rears bled free of bubbles, however when I bleed either of the two fronts air is getting sucked into the system. I've pumped a ton of brake fluid through these things, didnt run out of fluid in the reservior, and even tried bench bleeding the new master cylinder twice.

Also, I've been using a one person bleeder line (the kind with a check valve the doesnt let bubbles back in to the system), and don't push the pedal quite to the floor. I've also gone up and down the brake lines looking for leaks, but cant find any. The only leak I can find is that one of my real cylinders is slightly leaky, but not very. Before I started I also had this problem of the rear wheels locking up real easily when I was doing about 5-10mph.

Help!

 

Sounds like you are doing everything correctly. Couple of ideas. Is the little adjustment screw in the end of the brake booster, you know the round headed screw that touches the brake master? Is it adjusted properly? There has to be a small clearance between it and the piston. Lastly, when bench bleeding the master, did you use full strokes? Need to go from stop to stop.

 

Thanks for your advice. I had a more experienced person stop by and look at the brakes and they informed me that the rear brakes were a bit messed up. I guess I'm kind of inexperienced with drum brakes so they looked ok to me, however it seems evident that the kid who owned the truck before me tried working on the brakes himself and didnt do such a hot job. Long story short, The air was coming from a leaky wheel cylinder, but I also needed new ratchet assemblies, some new brake line, and a few more parts in there. Fortunately the mechanic had some left over parts from another kit that he could use.

But, as usual, when one problem gets fixed at least one more is bound to pop up. The U-joint on the front right wheel is about to sheer apart, and its looking like i have a bad transmission mount.