Novak Conversions Jeep Wrangler TJ engine mounts

No brakes when backing up

astjp2

astjp2

TJ Guru
Original poster
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Joined
Aug 22, 2018
Messages
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Utah and Alaska
With all of the work I did, 4.56’s replaced the transmission and installed the atlas. Bled the brakes, found one fitting I didn’t get tight enough, and rebled. When I let sit for a minute or so, drive forward good pedal, back up and goes to the floor. Pump in once or twice and it has good pedal, but if I repeat same thing? Not sure what it could be. Considering a potential issue with the master cylinder, or maybe how the caliper sits in the mount or a leak I have not found?

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Maybe start simple with a gravity bleed...make sure the reservoir is full...crack open passenger rear...let it run out and watch for bubbles to stop.

-Mac
 
astjp2 said:
Doesn’t happen when going forward, only reverse.
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That wasn't the question. The question is how does the master know? It doesn't and can't. There is not a little shift button on the side of the master that is used to tell it to act differently in reverse. It acts the same in forward or reverse directions.
 
astjp2 said:
It doesn’t, but I am out of ideas as to why it only happens backing up.
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You have caliper piston knock back or something that mimics that, find it. The dead solid way to tell is if you have it, and then can pump the pedal back up and get brakes back again until the next time knock back happens.
 
mrblaine said:
You have caliper piston knock back or something that mimics that, find it. The dead solid way to tell is if you have it, and then can pump the pedal back up and get brakes back again until the next time knock back happens.
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Ok, is that where a piston is retracting too much into the caliper? Because that is what is happening. I can pump it up. Oh and it’s not too hard to get it to lock up the tires, I just don’t see a reason to panic brake.
 
astjp2 said:
Ok, is that where a piston is retracting too much into the caliper?
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No, the pistons are automatically retracted into the caliper when you release the brake pedal. That is why piston seals are square cut and then installed in a groove that has an angled face. If they don't retract a slight amount when the pressure is released, they drag too much.
astjp2 said:
Because that is what is happening. I can pump it up.
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Make sure that there is no other tire movement except the forward and reverse. If you are also turning left or right at the same time, then it can be something contacting the caliper body or brake line pushing the caliper body and that is pushing the piston in. It can be as simple as a loose rotor leaning over and pushing against the pistons.

I had a buddy who was convinced that shifting from reverse to drive was pushing his caliper pistons in. Turns out he had a ruined wheel bearing in his front hub kit. He was backing out of his driveway which was sloped pretty good and as soon as he got to the end of using reverse, he would turn the tires to get up on the street which would lean the rotor over and push a caliper piston in.
astjp2 said:
Oh and it’s not too hard to get it to lock up the tires,
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I'm not there, I'm not driving it, I'm just going by what you said, nothing more.
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astjp2 said:
I just don’t see a reason to panic brake.
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No one said you should be panic braking. I would just expect a lot more performance out of that set up than our pads in stock calipers.
 
mrblaine said:
No, the pistons are automatically retracted into the caliper when you release the brake pedal. That is why piston seals are square cut and then installed in a groove that has an angled face. If they don't retract a slight amount when the pressure is released, they drag too much.

Make sure that there is no other tire movement except the forward and reverse. If you are also turning left or right at the same time, then it can be something contacting the caliper body or brake line pushing the caliper body and that is pushing the piston in. It can be as simple as a loose rotor leaning over and pushing against the pistons.

I had a buddy who was convinced that shifting from reverse to drive was pushing his caliper pistons in. Turns out he had a ruined wheel bearing in his front hub kit. He was backing out of his driveway which was sloped pretty good and as soon as he got to the end of using reverse, he would turn the tires to get up on the street which would lean the rotor over and push a caliper piston in.

I'm not there, I'm not driving it, I'm just going by what you said, nothing more.
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No one said you should be panic braking. I would just expect a lot more performance out of that set up than our pads in stock calipers.
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Thanks Blaine, I need to check how the brake lines are affecting caliper movement in a turn. Wheel bearings are new, ball joints are new, so hopefully it’s simple.
 
I found my problem, I need to trim a piece of steel or flip the calipers left to right. When I got the toe correct it widened the tie rod ends of the knuckles and that created an interference problem with the caliper.
 
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