[Diesel X]

The brake pedal slowly goes to the floor when pressure is applied. It has a new vacuum pump, new power booster, and a new master cylinder. All the brake lines and the ABS valve under the cab on the frame rail has been bleed more then a couple of times. The left rear brake was out of adjustment, but it was adjusted and still the same. The caliper pin slides need to be cleaned and greased. The brake pads and shoes all have good life left to them. When you drive it there seems to be a delay in the power brakes, then it grabs hard then seems normal, but then the pedal goes to the floor slowly. The truck sat for a couple of years, so could this be a stuck caliper or wheel cylinder? Could it be a collapsed brake line? The thing is I think it is is the new power booster. The vacuum pump makes a noise like it is by passing the vacuum when it is connected to the power booster. When you disconnect the vacuum line from the booster and put your finger over the line to draw the vacuum the pump stops making the noise. I think thats all the details. Any ideas? Thanks in advace.

 

[speeddemon31176]

A bad brake booster would give you a rock hard pedal all the time and you would barely be able to stop if you could get it stopped. I would look under the dash at where the rod comes through from the master cylinder and see if it is leaking there. I would also look for leaks at the calipers, wheel cylinders and check all lines thoroughly. You have either got a leak somewhere or there is still air in the system. So you know there is a bleeder on the RABS valve as well. You could have air trapped in there.

 

[DieselDanF-350]

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[Diesel X]

The fluid level is the same . Tried to look for leaks but did not see any. Will try to to bleed them again. Would a mighty vac bleeder be the best way? Is there a possibility that the RABS valve is bad? If so is that a dealer only part? On the vacuum side of the question why would the vacuum pump bypass air out the back when connected to the power booster then stop when you disconnect it and put your thumb over it? It has good vacuum on your thumb. And you can hear the air as a strange noise that shouldn't be there. I noticed that the brake light on the dash stay's on.

 

[monster-energy-825]

well it sounds to me that you have air in your lines so just keep trying to bleed them and see where you end up.

 

[Tom S]

I say bad master cylinder or a leak. There are very easy ways to make a pressure bleeder which is very handy. The directions were posted in the last two weeks.

 

[Diesel X]

Counting the original master cylinder it is the third one on it since the problem started . Not saying you aren't right. Going to re-bleed the system and see what I get.

 

[Diesel X]

Just came back in from bleeding the brakes again. The RABS seemed to have air in it and I Mighty vac it quite a bit. Now not only is the brake light on so is the abs light. It felt like there was some improvement in the pedal feel so I went down the street to see what felt like. Seems like there is no power brakes now, but it isn't grabbing as bad as before. Thought for a second it was going in the direction before the abs light came on. Thinking maybe two things going on here, air in the RABS valve and the power booster is bad. Anyone got any ideas? Got called in to work so I'll try some more tomorrow.

 

[STROKER #1]

There are an upgraded brake booster made by ford, is something named: no loose boost brake, or something like that, I dont remember right now.

Check it out. Good luck.

 

[STROKER #1]

here you are, I found this:
"1997 and earlier diesel trucks equiped with vacuum power brakes--Low/creeping pedal:
Many owners have complained of a low or creeping brake pedal on their trucks, often mistaken for a bad master cylinder or Rear ABS valve. If the condition occurs after the vehicle has come to a stop, and no other brake concerns are found, (worn or out-of-adjusted brakes, ****ed pads, or hydraulic problems) the condition is normal and the result of the vacuum pump replenishing the vacuum inside the power booster. Ford has developed a Zero-Loss Travel brake booster to correct this condition if the customer finds it unacceptable. This part is only for use on diesel-equiped trucks--P/N F5TZ-2005-CA--and is not a service replacement; it must be ordered by the part number, not vehicle application.

 

[Aljay]

here you are, I found this:
"1997 and earlier diesel trucks equiped with vacuum power brakes--Low/creeping pedal:
Many owners have complained of a low or creeping brake pedal on their trucks, often mistaken for a bad master cylinder or Rear ABS valve. If the condition occurs after the vehicle has come to a stop, and no other brake concerns are found, (worn or out-of-adjusted brakes, ****ed pads, or hydraulic problems) the condition is normal and the result of the vacuum pump replenishing the vacuum inside the power booster. Ford has developed a Zero-Loss Travel brake booster to correct this condition if the customer finds it unacceptable. This part is only for use on diesel-equiped trucks--P/N F5TZ-2005-CA--and is not a service replacement; it must be ordered by the part number, not vehicle application.

Nice find !

 

[speeddemon31176]

That is a good find but I am surprised by that as well considering that I do not have that special booster and my pedal is right up top when you apply the brakes and if you stab the brakes in a panic type situation you had better be prepared to eat windsheild.

 

[Diesel X]

Just got outside and started the truck and now ABS light is out but the brake light is still on. Didn't do anything between last night and now to get the ABS light to go out. It went out on it's own. Also last night some times when I would pump the brakes the brake light would go out for a second or so then come back on. Still goes to the floor though. I'll check on that no lost booster from Ford. Thanks for all the help so far.

 

[Diesel X]

Called about the zero lost brake booster and the parts guy said after talking to him that is supposed to be my stock replacement. Go figure. The price is a shocker, it lists for 304$. So I guess that's the next step.

 

[speeddemon31176]

If the ABS light went out on its own and the pedal is still going to the floor and the brake light would go out and come back on while pumping the brakes then you have air in the system still and that is why you have all of those symptoms. There is no other explaination for all of those symptoms. Don't go wasting money on a part that will not fix your issue. The best method I have ever used short of a pressure bleeder is to use a bottle with brake fluid in it and a hose connected to the bleeder. You have to make sure the master cylinder does not even come close to running out of fluid.

 

[madpogue]

Did you "bench" bleed the master cylinder before installing it?

 

[Diesel X]

Did you "bench" bleed the master cylinder before installing it?

Yes it was. Guess I'll try and bleed the system more.

 

[Diesel X]

Update to the brake problem. I bleed the crap out of the system and it still wasn't right. The thing with the vacuum pump making noise had me thinking that the booster was bad.Well I bit the bullet and took a chance and bought the no lost booster. Well that was it. After looking at them I think it was the wrong one the mechanic put on the truck. Not 100 percent sure. There is a difference in appearance so that's my guess why it was wrong. Going down and talk to him about it today. Thanks everyone for the help. Now on to the next problem.

 

[STROKER #1]

Update to the brake problem. I bleed the crap out of the system and it still wasn't right. The thing with the vacuum pump making noise had me thinking that the booster was bad.Well I bit the bullet and took a chance and bought the no lost booster. Well that was it. After looking at them I think it was the wrong one the mechanic put on the truck. Not 100 percent sure. There is a difference in appearance so that's my guess why it was wrong. Going down and talk to him about it today. Thanks everyone for the help. Now on to the next problem.

Well, let us know how it goes, keep posting here. ( Maybe someone is the winner.:bowfast: LOL)