Another spongy brake pedal problem??
Thread Starter
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Mountain Pass
Joined: Mar 2005
Posts: 133
Likes: 0
Another spongy brake pedal problem??
Well the truck is a 90 f-350 2wd,disc front drum rear.Its my uncle's truck he tells me my pedal is spongy and it sinks to the floor,so im like ok it's probly the master or a wheel cyl.I check the rear wheel cyl's and no leaks so i adjust the brakes cause the shoes are like @ 70%.Front pads kinda low so i replace them,So im thinking the master is bypassing ,replace master bench bleed it,manually bleed the system r/r l/r r/f l/f,no air clean fluid so the pedal is hard.Start the truck and the same thing SPONGY PEDAL s%#t and the rabs light is on.what do you guys think, i tried a search and read something about bleeding the ABS but dont know how PLEASE help ive never ran into this before sorry for the long post but i need help!!!
Post Fiend
Joined: Jan 2005
Posts: 8,402
Likes: 10
You will find the RABS valve bolted to the left side frame just about below the driver`s feet. There should be a bleed screw on it. Just bleed as normal. If that does not improve matters you may have a faulty RABS valve. It can fail such that with the pedal under constant pressure the pedal slowly sinks to the floor. Good luck.
Tuned
Joined: Oct 2003
Posts: 446
Likes: 4
From: Grayling, MI
A few months ago I had no rear brakes on my 95 F 350 and a real low pedal. I bled the brakes and replaced the master, but it turned out to be the RABS valve. I ended up bypassing the RABS by reflaring the lines with new fittings at the RABS with a union.
I had a thread going on here about this. Not sure how to put in a link, but you should be able to find it with an advanced search with my user name.
The brakes have never been better on this truck. I don't remember if it had a good pedal when not running or not, and I didnt have any lights either. Hope this helps. Good luck.
I had a thread going on here about this. Not sure how to put in a link, but you should be able to find it with an advanced search with my user name.
The brakes have never been better on this truck. I don't remember if it had a good pedal when not running or not, and I didnt have any lights either. Hope this helps. Good luck.
New User
Joined: Jan 2003
Posts: 16
Likes: 0
I had the same spongy brakes on my 94 F350. I installed a hydroboost setup and rear disk brakes and its perfect now. I had already replaced the rear wheel cylinders,master cylinder, and bled them numerous times, so the problem had to have been the vacuum booster I guess.
I never even thought about the RABS valve but its still in there and untouched so youd think if that were faulty it would still be spongy with the new setup.
I never even thought about the RABS valve but its still in there and untouched so youd think if that were faulty it would still be spongy with the new setup.
Thread Starter
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Mountain Pass
Joined: Mar 2005
Posts: 133
Likes: 0
OK heres a up date,I blead the rabs no air came out still the same thing.I was looking back at some threads and found some thing about a diff master it has a little bigger bore any body hear about this?Im going to replace the master again tomarrow ill keep you guys updated,ill also replace the rabs of course one at a time ill keep u updated.This sucks!!!!!
Laughing Gas
Joined: Oct 2005
Posts: 1,227
Likes: 42
From: The OC
Your booster is probably worn out. Start the truck, push the brake peday and listen for what sounds like an air leak at the booster. My F-150 does the same thing. All new brakes and bled complete. Spongy pedal action and you can clearly hear the vacuum from the booster.
Thread Starter
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Mountain Pass
Joined: Mar 2005
Posts: 133
Likes: 0
Well i could hear a little air leak from the booster,but i thought that a faulty booster would make the pedal harder not softer,On your 150 did you replace the booster and did it fix the spongy pedal?
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Laughing Gas
Joined: Oct 2005
Posts: 1,227
Likes: 42
From: The OC
Haven't replaced the booster yet. Did everything else to the brake system. My Haynes manual troubleshooting section states "power brake booster not operating properly" if excessive effort is required to stop the vehicle. I don't hear any hissing from any of my other cars boosters, so I am assuming my unit is worn out. My truck stops fine, just not like I think it should.
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