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Discussion Starter #1
So I thought I had this fixed after bleeding all the fluid out of the brakes.
They have worked fine for a few months and then yesterday the first reasonably hot day of the year I drive to TSC with no problems, I park. I go int the store to get feed, come back out get in start to drive and a brake is dragging.
I am glad I did not put the new rotors on!
I am going to rebuild the calipers which I am pretty sure are not the problem.
I have a new master cylinder I bought awhile back. I am going to bench bleed and replace.
For such a basic brake system it is a PITA!
I mean all there is, is a master cylinder, proportioning valve, lines and calipers.
Front flex lines have been replaced as well as all four calipers/pads. The calipers were lubed up, been bled to death. The only thing left is the master cyl and proportioning valve, and I have never seen a bad proportioning valve and since it has no moving parts it is highly unlikely to cause this issue.
If it were not for these brakes I could probably like my Jeep. LOL
 

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I've only seen collapsed lines and worn out calipers cause this. I've been working on the brakes of my scrambler for many weeks (only for a little time on the weekends) but am close to having them working properly...my desire to keep working brakes is very low right now.


Good luck, I hope you find something easy to fix it.
 
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Discussion Starter #5
I've only seen collapsed lines and worn out calipers cause this. I've been working on the brakes of my scrambler for many weeks (only for a little time on the weekends) but am close to having them working properly...my desire to keep working brakes is very low right now.


Good luck, I hope you find something easy to fix it.

Yep, lines and calipers were my thought a few years ago. They have been replaced with new. I am going to rebuild the calipers this time. I am going to go ahead and replace the MC also. My thought on it, is it may not be releasing pressure. It's just odd it only does it when it starts getting hot outside and then not all the time.
 

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Yep, lines and calipers were my thought a few years ago. They have been replaced with new. I am going to rebuild the calipers this time. I am going to go ahead and replace the MC also. My thought on it, is it may not be releasing pressure. It's just odd it only does it when it starts getting hot outside and then not all the time.

Are you sure the plunger in the master cyl is returning all the way?
 

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Discussion Starter #7
Are you sure the plunger in the master cyl is returning all the way?

I have had the plunger issue with other vehicles. When they they had plunger issues I had an issue everytime I drove, not unless it was very short distances. This Jeep will not do it in cooler temps, only when it is hot outside and then it's very intermittent.
 

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Discussion Starter #8
Planning on working on the brakes today. I don't know what I'll get done today. I am going to change the M/C and check the pushrod length sine the M/C will be off. I also want to rebuild the calipers and replace front rotors, maybe rear rotors also if i don't run out of gas. LOL If I do, the Jeep isn't going anywhere. LOL
At least it will be easier to get the wheels off since I have the new hi-flo fittings and good hoses. I can use the impact gun and knock them out quick like an old retired disabled NASCAR mechanic in a wheel chair missing fingers and one leg, blind in one eye, cataracts in the other, having a lack of enthusiasm to work on anything anymore. I suppose I should get started before this is all I do today. LOL
 

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Discussion Starter #9
I did not get far with the brakes this morning. I bled these brakes to death this past winter. I insure I did not overfill the reservoir. This morning I went out starting to remove the M/C and I noticed it was overfilled, within approx. 3/8ths of an inch from the top of the cap. I do not know why it had that much fluid, especially when it was at the correct level this winter when I bled. Anyway, I took out around 5-6 cc of fluid.
There is not suppose to be any thermal expansion of the fluid, or very little.
So I stopped, and I will drive and see if this does anything, if the very intermittent issue returns.
Like I said before this issue shows it self more in the heat of summer and it's been getting hot here, especially the time of day I drive.

It may also explain why I can drive somewhere and it's fine, come out start driving and the front brake or brakes are dragging.

One thing I did see is where the proportioning valve is mounted. I never noticed it till today. LOL
Oh Well, It may be another week or two before I drive again.

I suppose I'll go bike riding now! Burn off all this energy an old retired disabled NASCAR mechanic in a wheel chair missing fingers and one leg, blind in one eye, cataracts in the other, having a lack of enthusiasm to work on anything anymore.

Oh, I'm not a NASCAR mechanic, but the rest or certain parts fit. LOL
 

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Check the caliper mounting bracket slide rail for wear too... newer vehicles have stainless wear pads, the TJs did not, and they get a divot that can hang the caliper, needs a bit of weld or a stainless sleeve to allow the caliper to slide
 

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Discussion Starter #11
Check the caliper mounting bracket slide rail for wear too... newer vehicles have stainless wear pads, the TJs did not, and they get a divot that can hang the caliper, needs a bit of weld or a stainless sleeve to allow the caliper to slide

Thanks for the suggestion. It's been done a few times. This is an on going intermittent issue.
 

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Discussion Starter #12
Removing the excess fluid seems to have just slowed the on-set of the dragging brakes.


I drove about 20 miles stop and go, everything was fine. I come out of my doctors office and the brakes are dragging. They could have been dragging already just not as bad. So with it sitting still with no air to go over brake to cool it down at the doc's office they just got worse.
When I got home I jacked the front. Both brakes on the front are dragging. I could not turn the wheels at all.
I jacked the rear and they were fine. I could turn them.


When I bled the brakes this past winter I lathered everything on the brakes with brake grease, the two front lines were replaced when this issue began. Both front calipers were replaced back then. I have rebuild kits for them now.

I have a new master cylinder I have not installed.


What do knowledgeable folks think I should do?
 

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^^On my home computer now so I can expand on the above.^^
NAPA part SE4890 is a right side caliper with a phenolic piston. Part SE4890S is one with a steel piston. The phenolic was used for several reasons. One being little to no heat transfer. The issue with Chrysler's original supplier is they cut/made the piston cold. Therefore during use, as it heated, it expanded ever so slightly and bound. It is unknown if replacement calipers with phenolic pistons are made in the same manner. My buddy recommends the steel piston replacements for this very reason.
Maybe this will help with your troubleshooting efforts. Let us know. If needed, I can PM you the tech line number for the company that supplies NAPAs calipers. You could call them and see if they are aware of the issue stated above.
 

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Discussion Starter #15 (Edited)
^^On my home computer now so I can expand on the above.^^
NAPA part SE4890 is a right side caliper with a phenolic piston. Part SE4890S is one with a steel piston. The phenolic was used for several reasons. One being little to no heat transfer. The issue with Chrysler's original supplier is they cut/made the piston cold. Therefore during use, as it heated, it expanded ever so slightly and bound. It is unknown if replacement calipers with phenolic pistons are made in the same manner. My buddy recommends the steel piston replacements for this very reason.
Maybe this will help with your troubleshooting efforts. Let us know. If needed, I can PM you the tech line number for the company that supplies NAPAs calipers. You could call them and see if they are aware of the issue stated above.

The OEM calipers were replaced. This sounds like it is the issue. I could not fing metal pistons for my Jeep so I went ahead and ordered phenolic. I don't off road.

This makes more sense. My Jeep had no issues till I moved here hauling a trailer full of stuff. Then the problem started. I replaced calipers but I also hauled the trailer somemore.

Very well could be the phenolic overheated. I can only imagine what they will look like when I tear into the calipers. I think I will also rebuild the old calipers since the ones on the Jeep have overheated several, several times. It also likely explains why this issue does not rear it's head in winter.
 

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Discussion Starter #17
Yeah, sounds like it will fix it. I'll have to see if there is a NAPA around here. Wish I had known about this phenolic stuff a few years ago!
 

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Discussion Starter #18
^^Check with NAPA^^ My bud showed me the computer screen today and it showed the steel option available. Didn't catch the cost, but at this point you probably just want it fixed. Good luck and stop teasing us with the puppy videos--just kidding!

Just remembered one other thing about the brakes.



I forgot to mention the pedal was hard.
The pedal does not go back to normal until the brakes cool and release or something else happens.


With only 25K on this Jeep you'd think nothing would be broke apart from the OPDA and blower resistors. LOL
 

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Discussion Starter #20 (Edited)
Yes, if the current thought about the piston sticking is correct it would cause the stiff pedal. JMHO, and someone else's opinion too. Ask around and see what others think. By the way, 6 Napa's around Mobile.



10-4 on NAPA. It's too bad Rock Auto did not have the metal piston.
Do you think the heat could have damaged the caliper housing? I intend to rebuild them.


I looked online at NAPA they are just showing the phenolic piston.
 
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