Brake pedal to the floor
09-11-2016, 09:33 PM
#1
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Brake pedal to the floor
So my front brakes locked up on me. 1993 F150 XLT Got it home and decided to replace everything. New Brake hoses, calipers, pads, brake booster, master cylinder, proportioning valve. Bled the system, no leaks. Started the truck and the pedal went straight to the floor, pushrod is adjusted out to 63/64 of and inch and no leaks. Re-bled the master cylinder and all wheels. Started the truck and same thing, pedal to the floor. I am lost and pissed. No leaks and no air. Any help would be appreciated. Thank you.
09-11-2016, 09:44 PM
#2
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Did you by chance install the front calipers on the wrong sides, driver side on the passenger side and passenger side on the driver side. When they are on the correct sides, the bleeder valves will be toward the top.
09-12-2016, 09:22 AM
#4
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Pedal to the floor but returns by itself usually means you have a leak or have not filled up the calipers with enough fluid yet to get them to grab. If it grabs and pulls to the floor itself and won't return unless you turn off the truck, that's usually a bad master or maybe even a vacuum leak in the brake booster line.
It sounds like you know what you are doing mostly - so I hesitate to ask if you slowly pumped the brakes after you turned on the truck to get the fluid levels in the calipers right - sometimes it takes 5-10 pumps depending on how far open the calipers were.
Only other things in the system I can think of would be the RABS valve and computer, but I doubt those would cause this problem.
It sounds like you know what you are doing mostly - so I hesitate to ask if you slowly pumped the brakes after you turned on the truck to get the fluid levels in the calipers right - sometimes it takes 5-10 pumps depending on how far open the calipers were.
Only other things in the system I can think of would be the RABS valve and computer, but I doubt those would cause this problem.
09-12-2016, 01:16 PM
#5
Pedal to the floor but returns by itself usually means you have a leak or have not filled up the calipers with enough fluid yet to get them to grab. If it grabs and pulls to the floor itself and won't return unless you turn off the truck, that's usually a bad master or maybe even a vacuum leak in the brake booster line.
It sounds like you know what you are doing mostly - so I hesitate to ask if you slowly pumped the brakes after you turned on the truck to get the fluid levels in the calipers right - sometimes it takes 5-10 pumps depending on how far open the calipers were.
Only other things in the system I can think of would be the RABS valve and computer, but I doubt those would cause this problem.
It sounds like you know what you are doing mostly - so I hesitate to ask if you slowly pumped the brakes after you turned on the truck to get the fluid levels in the calipers right - sometimes it takes 5-10 pumps depending on how far open the calipers were.
Only other things in the system I can think of would be the RABS valve and computer, but I doubt those would cause this problem.
09-12-2016, 04:13 PM
#6
RABS unit - at the junction of the brake lines from the master cylinder and where they head to the rear, just inside the frame rails on the drivers side of the truck...
bleed it and you will likely be fine
bleed it and you will likely be fine
09-13-2016, 08:23 PM
#7
Senior Member
Seems like you know what you're doing - tossing these out for consideration, as they've tripped me up on past brake work.
1) Didn't get the new master cylinder bench-bled properly.
2) Didn't get the star adjusters on the rear drums dialed out far enough.
3) Didn't bleed in the proper order - which I figure to be Right Rear, Left Rear, Right Front, Left Front.
4) Didn't have the self-bleeder thingie primed with brake fluid so as not to pull air back in on the pedal retract.
Hope this helps.
1) Didn't get the new master cylinder bench-bled properly.
2) Didn't get the star adjusters on the rear drums dialed out far enough.
3) Didn't bleed in the proper order - which I figure to be Right Rear, Left Rear, Right Front, Left Front.
4) Didn't have the self-bleeder thingie primed with brake fluid so as not to pull air back in on the pedal retract.
Hope this helps.
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10-15-2016, 09:06 PM
#8
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So I replaced the ABS hydraulic unit as well now. Bled the system and got good pedal resistance, started the truck then pedal to the floor again! I then disconnected the vacuum line off of the brake booster just for ****s and giggles and I got in the truck and pressed the pedal and the pedal had great resistance. I hooked the vacuum line back up and pedal to the floor. Would that mean I have a vacuum problem?
10-16-2016, 07:44 AM
#9
Senior Member
Eh, suppose it's possible that the new booster is bad out of the box, but as you describe things, still thinking the issue is somewhere with the brakes proper.
Does the pedal go all the way to the floor, or just stop short as the front pads grab the discs? If the pedal just stops short and you changed the rear drum shoes, perhaps double-check that the star adjusters are dialed out far enough...?
Relating to an experience where I didn't turn the drums, and there was enough of a lip on the edge that required the star adjuster be dialed in to get the drum on, result was that the pedal went to almost the floor. I then went in through the backing plate to get the adjuster dialed out far enough where I had enough pedal and the auto-starwheel adjustment could take over.
Does the pedal go all the way to the floor, or just stop short as the front pads grab the discs? If the pedal just stops short and you changed the rear drum shoes, perhaps double-check that the star adjusters are dialed out far enough...?
Relating to an experience where I didn't turn the drums, and there was enough of a lip on the edge that required the star adjuster be dialed in to get the drum on, result was that the pedal went to almost the floor. I then went in through the backing plate to get the adjuster dialed out far enough where I had enough pedal and the auto-starwheel adjustment could take over.
10-16-2016, 12:41 PM
#10
If the brakes are indeed properly bled, there would be an incredibly high pressure in the brake lines if you pushed the pedal all the way to the floor. There has to be air in the system somewhere. If you disconnect the booster vacuum, does the normal resistance you feel in the brake lines actually hold the truck against the transmission / brake normally?
I'm not sure on a truck as old as yours, but on many modern vehicles it is not possible to bleed the ABS controller at home. The dealers have a special multi-thousand $$ machine for this. If you get air in the controller, the only solution is the dealer.
I'm not sure on a truck as old as yours, but on many modern vehicles it is not possible to bleed the ABS controller at home. The dealers have a special multi-thousand $$ machine for this. If you get air in the controller, the only solution is the dealer.
