dumb rabs question
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Senior User
Joined: Mar 2009
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From: Washington County, Penna
dumb rabs question
ok working on the brakes of my 89 f250, at the rabs module, i see that a previous owner has worked on brake lines previous to me getting the truck... my big question is is that i can build plenty of pressure to the front but only trickles out of the rear... my big question is which one on the rabs module is the inlet ( coming off the master ) and which is the outlet (going to the rear of the truck ). i know it sounds dumb but im wondering if the P.O. got them mixed up
Post Fiend
Joined: Jan 2005
Posts: 8,402
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Shouldn`t be possible to mix them. The pipe from the master cylinder is 1/4 or 5/16in pipe while the pipe going from the RABS module to the rear brakes is normal 3/16in. The larger dia pipe from the master cyl should go to the front port on the module as I remember.
There is a solenoid operated valve in the RABS module that, when commanded by the computer, prevents any brake fluid getting to the rear brakes. It is possible that it has stuck.
There is a solenoid operated valve in the RABS module that, when commanded by the computer, prevents any brake fluid getting to the rear brakes. It is possible that it has stuck.
Post Fiend
Joined: Jan 2005
Posts: 8,402
Likes: 10
Good question. It is possible but unlikely, that it would be an electronic control fault. Easy to find out, just unplug the electrical connector at the RABS module on the frame rail and see if that solves the problem.
More likely to be an internal problem due to corrosion. Possibly dismantle it and try to clean it and check that the solenoids are good. Or just bypass it with a short length of hard line or replace it with a reman one.
More likely to be an internal problem due to corrosion. Possibly dismantle it and try to clean it and check that the solenoids are good. Or just bypass it with a short length of hard line or replace it with a reman one.
i ain't rite
Joined: Mar 2005
Posts: 65,579
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From: Marlboro Mental Hospital.
the rabs in my 88 have never worked properly from the day i got it with 4 miles on. by the time the truck had 3000 miles on it, the rabs valve was eliminated from the brake circuit.
that was one of the best modification i ever did to the truck.
that was one of the best modification i ever did to the truck.
