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post #1 of 12 Old 07-19-2019, 03:44 PM Thread Starter
tfo219
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Brake job

Hey guys I have an 04 Jeep Grand Cherokee and I recently replaced the line going from the HCU to the rear of the vehicle. The brakes were fine after that. I then test drove and realized a front caliper froze up. I replaced the caliper and pads and then bled that caliper, brakes were a little worse but still fine. I decided I wasn’t happy and proceeded to bleed all calipers, long story short no matter how much I bleed the pedal still goes to the floor and doesn’t tighten up after pumping.

Tried bleeding the master cylinder and they would tighten up after pumping but went back to normal when the car started up. I went ahead and tried to bleed the HCU and now the brake and ABS lights are on. I’m done working on it, just trying to fix it enough to drive and sell it.

I’m new to the forum also, thanks for any help in advance!

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post #2 of 12 Old 07-22-2019, 09:13 AM
Mattyjm
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Originally Posted by tfo219 View Post
Hey guys I have an 04 Jeep Grand Cherokee and I recently replaced the line going from the HCU to the rear of the vehicle. The brakes were fine after that. I then test drove and realized a front caliper froze up. I replaced the caliper and pads and then bled that caliper, brakes were a little worse but still fine. I decided I wasnít happy and proceeded to bleed all calipers, long story short no matter how much I bleed the pedal still goes to the floor and doesnít tighten up after pumping.

Tried bleeding the master cylinder and they would tighten up after pumping but went back to normal when the car started up. I went ahead and tried to bleed the HCU and now the brake and ABS lights are on. Iím done working on it, just trying to fix it enough to drive and sell it.

Iím new to the forum also, thanks for any help in advance!
Sorry for the delay. I had to go out and smoke a ciz, then took a shiz, then read this three more times before attempting to reply.

I have a few questions for you.

Did you only replace one caliper and one set of pads? And somehow the brakes were worse after you did this?

When the brakes go back to "normal" after starting the engine, does normal mean bad? Or good? Or normally good?


Possibly a stupid question here, but have you found any leaking fluid?

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #3 of 12 Old 07-22-2019, 09:40 AM
jtec
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Could be the devil's in the details.

Things were once so easy.
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When I see the price of OEM I think aftermarket.
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post #4 of 12 Old 07-22-2019, 12:09 PM Thread Starter
tfo219
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I replaced one caliper and the pads on each side. When I say normal I meant to say they go all the way to the floor again. There’s no leaks anywhere that I can find and tightened up the fittings just to be safe. I’ve been reading around and ppl recommend bleeding the lines furthest from master cylinder first then working way up. But even when I tried this the pedal still went to the floor.

Maybe I am bleeding them wrong?

Very much a rookie at this stuff 🙂
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post #5 of 12 Old 07-22-2019, 12:58 PM
Uniblurb
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Correct, if you're doing a full brake bleed you start on the furthest caliper in following this order; passenger rear, driver's rear, passenger front, finally driver's front.

There's several different methods for bleeding a caliper and if you have a helper have them push the pedal down then you open the bleeder screw. Have the windows down say "hold", then you tighten up the bleeder screw, then say "let off". Commands are simple; "push", "hold", and "let off". It's best to do this about 3 times on each caliper. I'll have a piece of hose on the end of the bleeder screw going into a jar to avoid a big mess.

Some will have a hose attached to the bleeder screw going into a jar of brake fluid then pump the brakes with bleeder screw open. This supposedly will push the air out but not let any back in. But sometimes if there's slop in the bleeder screw threads the air can be pulled back in.

There's also a "speed bleeder" type bleeder screw which lets fluid out but supposedly not air back in.

Likely when you replaced your rear line or the front caliper you let the master cylinder go dry and have air still trapped in it. Normally it takes "bench bleeding" to get the air out of a MC and you can actually do this with the MC still attached to the brake booster. You'll need to get a MC bench bleeder kit with hoses/fitting and at the end is a diagram of the setup. I had my wife help on this one while I watched for air coming out of the hoses in the bottom of the MC reservoir. It just takes slow pumping quite a few times.

How did you bleed the HCU by itself since I've never heard of this? It's difficult to get air in the ABS but if you stomped on the brakes with lines loosened to it you could have pulled air into it.

Lastly keep in mind when correctly installed caliper the bleeder screw on the caliper will always be at the top so air can escape. The rear calipers can be switched so this is backwards with bleeder screws at the bottom and the brakes never will pump up. Check your front caliper to make sure they didn't sell you the wrong side caliper and the bleeder screw should be at the top and not the bottom.

Below is the diagram for "bench bleeding" a MC and good luck. Forget the "wooden dowel" in the instructions when doing this procedure with MC still attached to the brake booster.
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post #6 of 12 Old 07-22-2019, 01:58 PM
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[QUOTE=tfo219;40686271]I replaced one caliper and the pads on each side. When I say normal I meant to say they go all the way to the floor again. Thereís no leaks anywhere that I can find and tightened up the fittings just to be safe. Iíve been reading around and ppl recommend bleeding the lines furthest from master cylinder first then working way up. But even when I tried this the pedal still went to the floor.

Maybe I am bleeding them wrong?

Very much a rookie at this stuff 🙂[/QUOTE


Are you doing this by yourself? Are you getting any assistance during your brake line bleeding process?

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #7 of 12 Old 07-22-2019, 05:04 PM
CarlJH
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I was wondering can you fool the ABS into working by supporting all 4 corners on axle stands, clamp off 1 brake hose so when you fire it up and put it in drive and apply the brakes 3 wheels will have brakes and will lock up but as 1 is clamped off the ABS will think the 3 are on ice so will cycle the HCU to release the pressure/trapped air?
Is this safe? has anyone tried it? does it turn all 4 wheels?
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post #8 of 12 Old 07-22-2019, 09:52 PM Thread Starter
tfo219
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The MC running dry is definitely a likely event as the first time I didn’t have any help and couldn’t be everywhere at once. I’ll double check the calipers to make sure they are positioned correctly. But it sounds like all I’ll need to do is bench bleed the MC and then bleed all calipers and I should be ok? Correct me if I’m wrong. I’ll get the chance to work on it again in a few days. I’ll keep you updated, thanks guys
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post #9 of 12 Old 07-22-2019, 10:26 PM
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It's difficult to not let the master cylinder go dry especially when replacing brake lines. But look at the #3-5 photos in the below write-up (too long to read) to see some ways to seal the top of the MC with tape and prevent fluid from coming out of a caliper line block in twisting in a piece of split fuel line.

https://www.jeepforum.com/forum/f310.../#post40058681

Just a tip on bleeding the MC that the front/back ports are 2 different fitting sizes while likely metric. Believe I'd go to a parts store which has a replacement MC and ask them to set you up with a bench bleeding type line system. Actually I've seen the plastic fittings and clear plastic lines come with a Cardone new or rebuilt MC.

Bleeding all the air out of the MC and calipers would be a good start. Can't guarantee your light for ABS will go out but if you never activated the ABS it could very well have both the brake and ABS lights go out. Good luck.

PS. Interesting concept CarlJH and I've seen some other methods for trying to fool the ABS to activate it. But sure would want the brake system to be free of air elsewhere so you don't end up with air in the ABS which wasn't there to begin with.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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post #10 of 12 Old 07-24-2019, 12:27 PM Thread Starter
tfo219
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*Update*

Bled the MC using the method provided, then bled each caliper and could see a ton of air coming out so that was a good sign. Did each caliper a few times then did a round 2 and the brake pedal was nice and tight. Mind you this was all with the key off. Started it up and the pedal went all the way to the floor and doesn’t seem as tight, yet the brakes are still WAY better and the car is now driveable. I’m just curious as to why this would have happened, or if it’s normal?

The brake and ABS lights also cleared off and haven’t popped up again.
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post #11 of 12 Old 07-24-2019, 01:54 PM
Mattyjm
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Quote:
Originally Posted by tfo219 View Post
*Update*

Bled the MC using the method provided, then bled each caliper and could see a ton of air coming out so that was a good sign. Did each caliper a few times then did a round 2 and the brake pedal was nice and tight. Mind you this was all with the key off. Started it up and the pedal went all the way to the floor and doesnít seem as tight, yet the brakes are still WAY better and the car is now driveable. Iím just curious as to why this would have happened, or if itís normal?

The brake and ABS lights also cleared off and havenít popped up again.
I ALWAYS have a person pump the pedal while I work the bleeder screws with the engine running. That's how you know you got it right. I have done plenty of single calipers on my own with no help, but you can't let the MC empty itself.

Your pedal still should not be going to the floor, though. It might the first time you start it up, but that's when you go back and bleed each caliper one more time to make sure it's full of fluid and not air. The pedal won't feel as hard as when you had the engine off, but it also isn't designed to put you through the windshield every time you want to slow down a little while you're driving.

Just make sure your MC stays topped off and capped while you're pumping and bleeding the brakes and you shouldn't have a problem. The braking systems on our WJs were top-of-the-line back when they were new, 15-20 years ago. They're still, in my opinion, very reliable and easy to work on compared to other vehicles that I've owned.

Good news to read that the lights went out. That's a big indicator that things are good again.

2002 Laredo. Baloo.
2004 Rocky Mountain Edition. Froggy Bandit. Wife's Daily Driver. PRISTINE! Stock height and may stay that way.....
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post #12 of 12 Old 07-26-2019, 06:20 AM
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Agree, your last bleed of all the calipers should be done with the engine running. I've also seen sometimes where the brake pedal will get a little tighter after a little bit of time like a week after a brake job has been done. Could be the fluid is settling down with fine air bubbles disappearing and/or some air may surface out of the master cylinder.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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