I replaced my brake booster cause the old one just rotted out or imploded. I tried to put the new one one which came with a new master cylinder attached to it. Trying my hardest to bleed the master cylinder properly to keep air from getting into the lines i still failed. My buddy helped me install new rear wheel cylinders since the old ones just broke when the bleeder screws were attempted to be removed. We bled all the brakes for a long time and not allowing the resevoir to run dry, the brakes are still messed up. The brakes are working at 60% compared to how they were before the booster crapped out. It seems that (1) there maybe air or something wrong with the RABSII Electro-Hydraulic valve=located inside the driverside frame rail. (2) the booster piston is not adjusted right to make the proper contact with the inside bore of the master cylinder. WHAT happens when applying the brakes fully with the pedal at the floor =I hear the front brakes making a grinding type noise or just noise from the front brake area. The brake pedal seems much stiffer now and just not near as responsive as they always have before. I would love to try and fix this myself but am at a loss for what to do about them. CAn somebody please help me out, it's a 93 XLT 4.0 4wd reg. cab truck, thanks!!!

 

Did you adjust the rod inbetween the master cylinder and the brake booster? It sounds like it is to long and not allowing full master cylinder piston travel.

Chad

 

Hey Thanks for the advice CAS FZ1; I thought that could be it but everyone told me, including Autozone, that since the booster came with a refurbished master cylinder that they had adjusted the booster adjustment rod to spec. I reckon i will unbolt that master cylder set up and shorten the adjuster rod , I really hope that is it because that darn ABS valve in the frame rail can't be bleed, we tried , and also according to another old post here , it must be removed and taken to the dealer. It's a real pain in the butt to haul a boat with 60% of ones brakes working, now i drive even more like a granny, lol. Tough ole truck things just finally started braking on it last fall, ie; brake booster, fuel pressure regulator, but nothen major, knock on wood. Thanks man, I'll keep the progress updated here! peace,

 

Go buy a chiltons or a Hayes manual they will tell you the proper rod length.

Chad

 

The Haynes just shows an exploded view but no specs on the secondary piston but thanks again , gonna go try to shorten it, thanks

 

Making the piston shorter did not work but making it longer seems to have helped! It feels like the brakes are at 80% maybe, something else is messed up but it's defenitely better. Thanks