Brake pedal bottoms, it barely stops

[thebadj]

'90/'91 ExplorerXLT 4X4 280k mi. (still doesn't smoke) After brakes started failing and hearing a big "sigh" under dash, I figured the diaphragm was gone and went and got a rebuilt brake booster. Followed the instrux, even made thrust piston gauge for really close to the 0.995" protrusion from booster into master cyl. per my Expl manual specifications. And the master cyl never gurgled after installation. But tho it has boost, the pedal still bottoms and it's dangerously slow coming to a stop. Has half the pads left, at least. Is this a master cyl problem? Haven't checked the rears; hell, they never take the load in this sorry 2 wheel abs. Any advice will be appreciated.

 

[BeauJ]

You didn't mention it, but did you bleed the brakes?

 

[thebadj]

mushy explorer

No, I didn't since I left the lines attached to the MC and moved it out of the way for the booster switch. May me a good idea, just do the leftie. John

 

[thebadj]

We bleed, we lock them up.

Sure enough, I bled a bunch of fluid out the driver's side front brake and bingo, I went out and locked 'em up. Thanks for whacking me back to basics. So, lesson: even when you do not disconnect any brake lines during a power brake booster swap, you may still need to bleed the brakes. Heck, fresh fluid in the reservoir can't be bad and it's too easy not to do it. John