Ok, so I replaced my brake fluid, bled them all until it was running clear, tested all of the calipers and they all work, replaced the vacuum booster, and still the problem persists
Bad brake booster or something else?
- Thread starter Joesmith
- Start date
Ok so the mechanic that did my engine lent me his vacuum tester and I took some video but I can not upload it here so I got a still of where the gauge was sitting at an idle around 750 - 800 rpm’s. This seems to be in the normal range from what I have read. Unless I’m reading it wrong.
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superj
Active member
that is acceptable vacuum.
so we are still at the point where the first pump of hte brakes is normal but all following require the pedal to go almost to the floor for the brakes to start working?
the only similar issue i have had to that is on an 87 cherokee i used to own. it sat a long time prior to me getting it, too. i ended up having to replace the master cylinder.
so we are still at the point where the first pump of hte brakes is normal but all following require the pedal to go almost to the floor for the brakes to start working?
the only similar issue i have had to that is on an 87 cherokee i used to own. it sat a long time prior to me getting it, too. i ended up having to replace the master cylinder.
Correct, the first push of the pedal seems fine, not sufficient to stop all the way, but the pedal feels normal and the brakes grip like normal…then subsequent pressing of the pedal, it is super stiff and hard to push and you have to floor it to get the Jeep to stop.
I figured that was an acceptable vacuum just wanted another pair of eyes to tell me so.
Was kinda already resigned to a new master cylinder. It’s the only thing left on the board.
BALLS!!!
Thanks for the assistance. I’m gonna order a master this evening and get it hooked up over the weekend, or I may take it back to the shop and have him do it, it’s been near 30 years since I did one and I remember not liking doing it
JPNinPA
Well-known member
Sry been traveling. So when you bleed the brakes do you do the pump and hold method? If so do you see the caliper clamping the pads to the rotor? Did you grease the slide pins? Does this symptom occur when bleeding?
Did all wheels bleed the same? None were slower or more pedal resistance to press to the floor?
Never look down on anyone unless you are helping them up - Jesse Jackson
Did all wheels bleed the same? None were slower or more pedal resistance to press to the floor?
Never look down on anyone unless you are helping them up - Jesse Jackson
JPNinPA
Well-known member
Describe what you mean by “tested” all the calipers.
Never look down on anyone unless you are helping them up - Jesse Jackson
JPNinPA
Well-known member
Vac looks ok. What changed you said you idled at or above 1k rpm?
What you describe first pump stiff second solid but not stopping still sounds like a crimped hard line or failing rubber line.
When you bleed it, it bleed normal? No slow flow??
Never look down on anyone unless you are helping them up - Jesse Jackson
I guess when it was idling at 1000 I wasn’t giving it time to warm up. After it warms up the ide drops to the correct rpm’s (around 750-800).
When I bled them I had my son pump them and hold so i could crack the bleeders, they all bled the same, none of them were slow or anything.
And while he was pumping I could see the calipers puck moving to clamp down on the rotors.
To test the calipers, I removed them. Used a c clamp to push the puck in. Put the calipers back on, and watched the puck as my son pumped the brakes and the puck moved back into clamping position and squeeze the pads against the rotors. They all seemed to work fine.
I was not the one pumping the brakes so I couldn’t say if the pedal was acting weird when he was pumping up the brakes.
Last night I pulled the booster back out and returned it, I’m going to get another one on the off chance that the one I got on Amazon might be crap. If I put another one on and it still does this, I think I’m just going to rip everything brake related off and just rebuild the whole system from scratch.
I really Fu**ing hate this chasing gremlins nonsense.
When I bled them I had my son pump them and hold so i could crack the bleeders, they all bled the same, none of them were slow or anything.
And while he was pumping I could see the calipers puck moving to clamp down on the rotors.
To test the calipers, I removed them. Used a c clamp to push the puck in. Put the calipers back on, and watched the puck as my son pumped the brakes and the puck moved back into clamping position and squeeze the pads against the rotors. They all seemed to work fine.
I was not the one pumping the brakes so I couldn’t say if the pedal was acting weird when he was pumping up the brakes.
Last night I pulled the booster back out and returned it, I’m going to get another one on the off chance that the one I got on Amazon might be crap. If I put another one on and it still does this, I think I’m just going to rip everything brake related off and just rebuild the whole system from scratch.
I really Fu**ing hate this chasing gremlins nonsense.
JPNinPA
Well-known member
When you press the brake there are two motions. One is the piston pushing out of the caliper and inner pad into the rotor. The second is the outer part of the caliper sliding into the rotor. This creates a pinch to the rotor. If the slides are dry and or frozen only one side is gripping.
You would see this in the pad wear.
It wouldn’t cause the 2nd pump of the pedal to be solid.
Big thing is why a 2nd pump. First hitting the floor or close may be air, leak, or fluid pushing past piston on master cylinder. But these dont make the 2nd press solid. Crimped line bad booster ir rubber line. Two you would notice when bleeding.
Never look down on anyone unless you are helping them up - Jesse Jackson
Exactly, you’re coming to the same head scratching conclusion I’m coming to. Everything seems to be working fine from what I can see while laying under the vehicle messing with the calipers. Bothe sides move freely, it’s all lubed up as it should, the pads aren’t showing any unusual wear…in fact the from pads are almost brand new because I did the brakes like a month before the engine blew up.
Like I said I’m going to try a new new booster, and I also have some new lines ready to order when I get paid again. If the booster fixes it, ya…if not, I’ll start at the flexible lines from the calipers and just start replacing everything
JPNinPA
Well-known member
You tube
https://youtu.be/QaUPC8TjzWA?si=H1BzSGuMGZOIcr5I
Never look down on anyone unless you are helping them up - Jesse Jackson
https://youtu.be/QaUPC8TjzWA?si=H1BzSGuMGZOIcr5I
Never look down on anyone unless you are helping them up - Jesse Jackson
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Ok I was incorrect, I installed the brake booster, and it is still doing the same crap. It’s just super hard to push the brake pedal now, and it doesn’t seem to stop goodly…and if I sit and hold the brake pedal, it slowly loses pressure and the pedal gradually goes to the floor now.
No it wasn’t, so I went back an re-installed it, and made sure it was aligned properly.
And it’s doing the same thing it was before I changed it I ordered a new master cylinder should be here tomorrow
JPNinPA
Well-known member
Verify check valve is working and your vac line actually is pulling vac.
You don’t have 2 check valves do you?
If you were able to bleed the brakes there shouldn’t be an issue with the master… but gi ahead and replace it if you want.
Never look down on anyone unless you are helping them up - Jesse Jackson
You don’t have 2 check valves do you?
If you were able to bleed the brakes there shouldn’t be an issue with the master… but gi ahead and replace it if you want.
Never look down on anyone unless you are helping them up - Jesse Jackson
Nope only one check valve, new master cylinder installed, check valve is working. Vacuum line is pulling as it should…still I have to jam the pedal down to get the Jeep to stop.
I’m getting super fu**ing frustrated.
I’m not stupid, but this just doesn’t make fu**ing sense. I have replaced or verified everything that could cause this. The only thing I haven’t messed with is the ABS thingy that’s right by the master cylinder.
When I installed this new master, I bench bled it, and I re bled it once it was installed. And I could hear what sounded like air pumping through that ABS thing when my son was pumping the brake pedal for bleeding.
Is it possible that has shat the bed or got air in there somewhere and that is causing this issue?
Or maybe it’s not hooked up right, or a wire isn’t connected?
JPNinPA
Well-known member
I wouldnt think air in the abs would lock up the pedal it woukd make it spongy as the air is let into the system.
https://youtu.be/nQRnKyVyMuQ?si=kTU8F3dU_fNzJc3Z
Never look down on anyone unless you are helping them up - Jesse Jackson
https://youtu.be/nQRnKyVyMuQ?si=kTU8F3dU_fNzJc3Z
Never look down on anyone unless you are helping them up - Jesse Jackson
JPNinPA
Well-known member
At the risk of sounding crazy….you don’t have anything in the way of the brake pedal that may stop movement???
As a test (without driving) can you remove the vac line and use a pump to pull a vac on the booster. Start the vehicle and test the brake. Reduce the vac and test the brake. If you pull 23 in and it works you might need to look for a vac leak to improve vac. If its still hard??? Its not the vac.
Is it still first pump soft snd 2nd solid?
Never look down on anyone unless you are helping them up - Jesse Jackson
As a test (without driving) can you remove the vac line and use a pump to pull a vac on the booster. Start the vehicle and test the brake. Reduce the vac and test the brake. If you pull 23 in and it works you might need to look for a vac leak to improve vac. If its still hard??? Its not the vac.
Is it still first pump soft snd 2nd solid?
Never look down on anyone unless you are helping them up - Jesse Jackson
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Lol nothing is crazy at this point.
But no, there is nothing in the way of the pedal.
I’m going to start pulling the calipers off next, and double check and make double sure they are all functioning, and replace the flex lines at the caliper.
At that point everything will have been replaced except the abs thingy and the steel lines.
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