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So as of right now I've replaced the brakes all around the master cylinder the brake booster lines wheel cylinder calipers. I can't find any leaks. The issue I'm running into is when the trucks off the brake pedal after a couple of pumps gets rock hard. But when I turn the truck on it gets spongy to the point where the brakes arnt working. Now Ive been bleeding the system and I've bleed the master cylinder. If I rapidly hit the brakes with it on it works for a second. I know because the brake light disappears. Any help or advice would be appreciated. My other concern is on the booster is the pushrod that slides into the rear of the master cylinder suppose to be able to slide out of the booster or is it suppose to be stuck in there.
The brake warning light is a separate issue, and it has nothing to do with the pedal feel. No, none of the pushrods are loose - they're all attached. With the engine off, there is no assist, so the pedal SHOULD be very difficult to press after a few cycles. Click this & read the caption:
The procedure to re-center the warning light switch is detailed in the Haynes manual, which you should keep in the truck, after you've read it cover-to-cover at least once:
Most pedal feel problems are related to the drums (which are usually neglected & worn). Read this caption & the NEXT two dozen (all the ones about the drum system):
Yeah, I'm in the same boat as you Logan. My pushrod can be pulled out using almost no force. The pushrod comes out with the rubber front seal still attached to it and the roughly 1" round base. I am having the exact same issue as you, truck off and the brake pedal is rock hard, start up the truck and the pedal falls straight to the floor. When I depress the brake pedal with the truck on I can look out the drivers door at the rear drum (wheel off) and see the brakes engage but with no pedal feel at all. I've put a brand new master cylinder, completely new rear drum brakes from wheel cylinders and shoes out to the drums themselves (both rear drums have been properly adjusted) and all the lines have been completely bled more than once.
Steve, I would assume that at this point the next step would be to replace the brake booster?
Don't assume - test. Read that caption so you understand how the booster is supposed to work. Then check if it actually works that way. If it doesn't, find one that does. I prefer good use OE parts from the JY, rather than cheap new imported junk (even the imported stuff with Ford/MotorCraft branding).
All the booster rods come out as far as o know. Ive uad several of these old truck. With lots of breaking issues. The rod have slide out of all of them.. check And make sure your not leaking fuild at the wheel cyclinders at the back drums that they are working correctly. Check that there isnt a froze caliper on the front. Check line running along the frame to the rear that it doesnt have a bulge. Then probably a flush and bleed the system starting at the rear passenger wheel. Rear driver wheel. Front passenger wheel then the front drivers.
Also if you let the master cyclinder get low while your bleeding it can suck air.
Have had it where i changed just the front caliper and had to bleed the entire system.
Alright, so I should have noticed when bleeding the system, but the front brake calipers appear to already be closed (pad pressed against the rotors). This position doesn't change when the pedal is depressed. The rear brake drums wiggle when the brake shoes actuate proving they work. What is the best way to go about unsticking the front calipers and preventing this from occurring in the future?
I've got 2 pictures I snapped real quick just now.
Those rotors need to be either turned or replaced. Either requires removing the hub from the spindle, so read all the relevant captions in that photo album. Start at the pic with the hammer, and keep clicking NEXT at the top Left until you get to the 4WABS group.
That caliper had been stuck for a minute. Id probably replace it over a rebuild the price and the time youd have in finding the right iring wouldnt be worth it. The rotor should be replaced. Because you probably wont find anyone to turn it. The best thing to keep this from Happening again is to use the truck more. I hope that this info helps and doesnt come accross as preachy or arrogant.
The truck was driving just fine when I parked it in February, so I know the calipers should be operational. When I removed the calipers the slide assembly was rusted stuck due to the sprinklers hitting it every day for 4 months in the South GA climate. I'm probably going to go ahead and remove the whole assembly and replace the hubs, rotors, calipers, and pads while I've got most of it apart already.
Just a little background on the truck, its just a farm truck that is used to go hunting and mess around with. Purchased it last September from the original owner and have been fixing stuff as it arises since then.
I really appreciate all the help that this forum's users provide and I've already bookmarked Steve's Super Motors page since it seems to be the only place for me to find some of these more useful diagrams.
06-04-2019, 10:20 PM
Brake help, on 80 bullnose
