Thanks Tim, that's exactly the part # I was looking for. We'll see what happens.

 

So did the booster cure the sinking pedal? I am working on a truck now that is driving me nuts, does the same thing you have described. The master cylinder, RABS valve, front brake calipers & pads, rear brake shoes and hardware have been replaced.....and still the sinking brake pedal. Unless the engine is off, then as soon as the brake booster is pumped down (no vacuum) the pedal feels great.

 

Yes that did fix his problem. He posted another thread about it but not sure where it is.

 

here it is
https://www.ford-trucks.com/forums/6...ighlight=brake

 

Thanks Tim.

 

I have the same problem as drgrcr1. I've replaced basically my whole brake system on my '97, booster, master cylinder, and all brake pads/disks and hardware all around, the works. The brake sinks when the truck is running whether in drive, park, or whatever. The only thing that I haven't replaced is some of the brake lines and the ABS module(which looks rusty) but nothing is leaking. We also replaced the vacuum pump. Any ideas?

 

Did you replace the booster with the specific part # I gave for the "Zero Loss Booster"? If not, that would be the next step. I need to do it on a new truck I have. I hate, the falling pedal.

 

I think it's a replacement from NAPA, but I just really wanna know if something's wrong or if that's just how it is. Thanks.

 

The truth is it's just a crap shoot on which trucks have the falling brake pedal. But I've driven ALOT of OBS's. And more often than not, the pedal fell. The one time I actually went to Ford and got the specific # booster for the Zero Loss, it fixed it. Pedal was solid. So the one from Napa won't be it. It was a booster Ford's engineers had to come up with to fix the problem. And if you can get it elsewhere, I'm not aware of it. But that doesn't mean you can't.

But the specific part # is in my writeup.