Brakes
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Laughing Gas
Joined: Mar 2006
Posts: 1,083
Likes: 1
From: Fitzpatrick Alabama
Brakes
I have replaced everything on my brakes, so I think I have got something that isn't any good. But when I disconnected the vacuum line from the brake booster, I had more brakes. What they are doing is when you push them, they will build up, but as you hold them they leak down under your foot. When I disconnected the vacuum line, they held tight? Does this mean I need a vacuum pump?
Senior User
Joined: Dec 2006
Posts: 344
Likes: 3
From: Byron New York
Originally Posted by AndysFords
What is a RABS and where is it?
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
Likes: 3
From: Ladner, British Columbia
Originally Posted by AndysFords
I have replaced everything on my brakes, so I think I have got something that isn't any good. But when I disconnected the vacuum line from the brake booster, I had more brakes. What they are doing is when you push them, they will build up, but as you hold them they leak down under your foot. When I disconnected the vacuum line, they held tight? Does this mean I need a vacuum pump?
A bit of pedal fade is normal for some of the late 80's early 90' trucks I understand. There is a fix somewhere on this forum for that if it bothers you. My 93' has a tendency to fade slowly. It just has not bother me enough to worry about it.
Since you pedal goes hard when you disconnect the vacuum from the booster the problem is most likely booster, vacuum hose or vacuum pump related or possibly a vacuum leak in any of the systems that use vacuum (i.e. heater control valve if you got one)
Seb....
Elder User
Joined: Aug 2003
Posts: 933
Likes: 0
From: Québec
I just had my Master Cylinder replaced with a Ford F 450 one. There is a Ford bulletin on this. The brakes feels quite better than before, firm and would not sink down, and the truck brakes much better. I had a 93 before and there was also always a little sinking, not to worry, but still anoying.
My problem is that the dam light is still on. I drove for about ten miles and the light went off. The mechanic told me he could not bleed one of the rear wheel cylinder and the valve you are talking about could not be bled because the bleeder is broken off the valve.
In my Haynes book they talk about a pressure differential valve and a RABS valve. I do not know what I have. I know I have a valve with lines connected to on the driver side. The books says that the pressure diffential valve have to be recenter if there is a leak of if you replace a component on the brakes.
I am really sick of that system, and sick to work on the truck in the driveway. I will take it back tomorow and let you know what else they find, probably a coupe of 100$ later.
My problem is that the dam light is still on. I drove for about ten miles and the light went off. The mechanic told me he could not bleed one of the rear wheel cylinder and the valve you are talking about could not be bled because the bleeder is broken off the valve.
In my Haynes book they talk about a pressure differential valve and a RABS valve. I do not know what I have. I know I have a valve with lines connected to on the driver side. The books says that the pressure diffential valve have to be recenter if there is a leak of if you replace a component on the brakes.
I am really sick of that system, and sick to work on the truck in the driveway. I will take it back tomorow and let you know what else they find, probably a coupe of 100$ later.
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Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
Likes: 3
From: Ladner, British Columbia
The mechanic told me he could not bleed one of the rear wheel cylinder and the valve you are talking about could not be bled because the bleeder is broken off the valve.
I had the same experience when I last tried to bleed my 93' rear brakes with the O.E.M. cyliders. Both bleeder valves were rusted solid and I could not get them to move. Ended up buying two new cylinders. I eventually got one of the two bleeder valves on the old cylinders to move by dis-assembling it on the bench and applying some heat. The other one was hopeless and just broke off.
I put lots of nickel antiseize on the new bleeder threads on the new cylinders so hopefully they will move the next time I need to use them.
The O.E.M. cylinder did not have a very good bleeder screw design if you ask me.
Seb....
I had the same experience when I last tried to bleed my 93' rear brakes with the O.E.M. cyliders. Both bleeder valves were rusted solid and I could not get them to move. Ended up buying two new cylinders. I eventually got one of the two bleeder valves on the old cylinders to move by dis-assembling it on the bench and applying some heat. The other one was hopeless and just broke off.
I put lots of nickel antiseize on the new bleeder threads on the new cylinders so hopefully they will move the next time I need to use them.
The O.E.M. cylinder did not have a very good bleeder screw design if you ask me.
Seb....
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Elder User
Joined: Aug 2003
Posts: 933
Likes: 0
From: Québec
I just drove the truck today, brake lights staid off all the time. The F 450 MC really made a difference. When you apply the brakes, what a feeling, firm, no sponge, no sinkin. Hopefully the problem is fix. May be there was a bubble in there that found a place to hide...
