Hard pedal
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5th Gear
Joined: Sep 2024
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Hard pedal
New here, 2005 f250 sd 6.8 v10. Master cylinder was going bad. Bought reman at parts shop, installed, full brake bleed and now have no brakes and very hard pedal. Someone suggested a bad booster. Installed a reman, no change. Still hard as rock. Put 4 more master cylinders on and 4 more boosters and a abs pump/ block. 10 cans of brake fluid. Also ordered a fomoco new master cylinder and still no change. I have tons of vacuum. Boosters also hold vacuum. No leaks or hissing. Vacuum system not hydro. No issues till i changed mc. HELP what is wrong here? 4 weeks on this repair. Had laptop in it and in 2 shops and no codes and no one can fix.
More Turbo
Joined: Jun 2009
Posts: 661
Likes: 186
From: Lakeland, MN
Have you pulled calipers, compressed them (if they will at all) then leaving them one by one off the rotor, press the brake a little bit, make sure each one will extend and compresses back with not too much effort. Make sure the shoes are sliding nice and easy in the guides, no binding. Lines could be blocked by junk going out from the previous master cylinder. Likely your going to end up going line by line trying to find the blockage if this is the case. You threw the parts cannon at it so do just a little more and replace all the flex lines.
Lead Driver
Joined: Mar 2006
Posts: 6,259
Likes: 438
From: IL
I'm not always up on all of this newer technology, but it seems to me that if you've replace the same parts multiple times with no improvement then those parts are obviously not the problem. Have you checked your ABS module? Usually when you have a hard unresponsive pedal and you've changed the easy parts, it boils down to a bad ABS module. If you crack the incoming lines on the module and press the brake pedal, it should go to the floor and spit fluid all over. Hold the pedal to the floor and tighten all the lines so air doesn't get sucked back in. Then refill the res. Then crack the lines open on the outgoing side of the module and press the brake pedal, if it's hard and unresponsive, then you've found your problem, but still, DO NOT let off the brake until you've tightened those lines back up because you'll suck air if you do. If it operates normally then your blockage is somewhere in your lines. Just out of curiosity, you did remove all the plastic plugs from the calipers before attaching the lines, Yes??
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5th Gear
Joined: Sep 2024
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Hard pedal
Changed abd module also. Rear calipers are new. Fronts are not. Everyone kept saying only motorcraft will work but cant find those anymore. We felt of caliper on driver side and could feel movement when pressing pedal. Whats got me buffaloed is trusk was pertand working fine till i changed mc and bleed brakes. Don’t know how any trash could get in plus when i bleed calipers i get tons of pressure blowing out fluid. It’s almost like calipers locked up. But they’re not. Rolls easy and have to stand and push hard just yo attempt to slow down. And wont even come to a stop everyone keeps thinking rebuilt parts were bad why I change so many times. Definitely not the issue after 4-5 of each and diff abs block. Im going yo front calipers next
Lead Driver
Joined: Mar 2006
Posts: 6,259
Likes: 438
From: IL
I bought my rear calipers and front calipers from autozone, Duralast brand, probably rebuilt units and I haven't had a problem mines a 2003 F350 4x4.. You have already changed over your soft lines also??? as suggested before, I would pull the calipers one by one and actuate each one. Of I also changed the MC I bought from NAPA, just whatever brand they sold me.
You're also sure that you have good vacuum on the booster? You're using a main port off the manifold, right?? It sounds like your soft lines are check valving except you say it rolls easy. But if you didn't change the soft lines, I would do that before anything else.
You're also sure that you have good vacuum on the booster? You're using a main port off the manifold, right?? It sounds like your soft lines are check valving except you say it rolls easy. But if you didn't change the soft lines, I would do that before anything else.
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5th Gear
Joined: Sep 2024
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Hard pedal
Rear lines have been changed. I took mc off booster cranked truck put hand over mc hole and it almost sucked my hand inside. Tons of vacuum. If 1 or both front calipershave locked up then it had to have happened as i was changing bad mc at the beginning. Is that even possible
Lead Driver
Joined: Mar 2006
Posts: 6,259
Likes: 438
From: IL
Rear lines have been changed. I took mc off booster cranked truck put hand over mc hole and it almost sucked my hand inside. Tons of vacuum. If 1 or both front calipershave locked up then it had to have happened as i was changing bad mc at the beginning. Is that even possible
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Laughing Gas
Joined: May 2024
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From: E TN
Pump the brakes with the truck OFF. Hold your foot on the brake pedal hard and start the truck, the pedal should drop if the vacuum booster is working. If it doesn't drop check the vacuum source and the booster.
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5th Gear
Joined: Sep 2024
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Hard pedal
Ok guy back at it. Pump brakes hold , crank track truck and pedal drops about 1-2 inch. Booster working??? Just put on 2 new front calipers. Pump brakes and bleeders squart out 6+ inches. Only thing that is not changed is front brake lines and on way to get them. Probably not the issue but what the hell. Put em on anyway. Still have a hard pedal. Some what easy but having to pust hard with both feet to try to stop
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5th Gear
Joined: Sep 2024
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Ok guys figure this out for me. I finally took truck to ford place and they changed booster and m/c and still hard pedal. I had ordered a booster from junkyard somewhere off wrecked truck and it came in so I took it to ford dealership and they put it on and it fixed the issue. So my question is why 5 other boosters from 3 different part stores would not work. All looked the same. Cannot get a new anymore only reman but remans won’t work🤷🏻
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