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  #1  
Old April 30th, 2003, 23:15
bchulett bchulett is offline
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Got Brakes?

Well guys here's an update....

I finally got my ill-braking '91 XJ down to the dealer to install the new $160 combination (proportion) valve I bought recently.... took a test drive and this is the biggest single improvement to date!

If you recall, I've been bitching about my brakes for two years now. As a review, since March 2000, I've spent a total of $2,793. with little or no improvements on these damn XJ brakes!

1991 XJ specs:
- original owner
- excellent service history
- 3" Rancho
- 31x10.5 BFG's
- no clunk & stopped good until 3/27/2000


Here's the chronology:
----------------------------
3/27/2000 - 114K miles ("original" rear brake shoes failed... all hydraulic components also original)

- got a brake job... the #2 special.
- new Raybestos PG Plus front rotors/pads
- new Raybestos PG Plus rear shoes/hardware kit
- turned rear drums

Cost: $480.00
result: rear shoes started sticking... clunking effect
----------------------------
12/19/2000 - 121K miles (after several "under-warranty" adjustments... rear shoes still sticking)

- new rear cylinders
- resurfaced outa-round drums
- warranty replaced the outa-round shoes

Cost: $126.00
result: rear shoes still sticking... pedal goes to floor under hard braking.
----------------------------
1/05/2001 - Involved in minor accident (slowly rear-ended F-350 as I rolled 15mph to a stop... w/brake pedal at floor)

- hurt me more than than her
- F-350 trailer hitch pushed everything back and broke the grill
- damaged ego
- deductable $100
- insurance paid $531.00

Cost: $700 ($100 + $300 ins. increase for three years)
result: brakes still don't work.... perfect driving record destroyed.
----------------------------
1/11/2001 - 122K miles (took the damn thing back to the tire company)

- discussed the poor brakes
- explained I wasn't leaving until we reached agreement
- I pay for new parts they supply labor except for master C
- replaced all rear components with Mopar OEM
- replaced front calipers with Mopar OEM
- replaced front pads with Raybestos PG Plus
- replaced front rotors with Raybestos PG Plus
- replaced master cylinder with Mopar OEM

Cost: $2,016
result: brakes still don't work.... rear shoes sticking... clunking... pedal goes to floor
----------------------------
4/26/2001 - 125K miles (took it to dealer for full inspection: said this is the way XJ's stop)

- told them it wasn't this way when it was new
- also told them to replace the brake booster

Cost: $493
result: brakes still don't work... don't want to spend anymore money... demoralized
----------------------------
4/30/2003 - 148K miles (it's 26K miles later.... front pads getting thin.... want to keep the Jeep... so I bought a new combo valve.... $160 bucks)

- took it to "five-star" dealer for installation
- replace valve, adjust rear shoes, bleed lines, "I" will test drive

Result: best brakes I've had in 3-years... almost got 'em to lock

DEALER NOW INSTALLING THE FOLLOWING PARTS:
- new Mopar front pads
- new Mopar front rotors
- new Mopar rear shoes
- new Mopar rear drums
- new Mopar rear cylinders
- new Mopar hardware kit
- after "I" test drive....
- new Stainless-Steel flex lines

Cost: TBD
final results: "I" will provide an update

Bob H.

Last edited by bchulett; April 30th, 2003 at 23:37.
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  #2  
Old May 1st, 2003, 04:00
Bill-93XJ's Avatar
Bill-93XJ Bill-93XJ is offline
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Bob, I feel your pain !!!

I promise to NEVER complain about my brakes again! Man, this is a horror story...... talk about changing out parts! Thanks for telling us all about your experience. If only someone had recognized earlier about the damned proprtioning valve !!!

This is why I love this board/group. You have saved some other poor guy the agony of repeating that whole deal. I have learned so much about my XJ here it is not even funny. My neighbor's wife drives a 2WD 95 XJ and he told me the fun they had with the CPS. Dealer (stealer) was into them for 500-600 bucks by the time it was done. Sometimes I think when I hear stories like that it is just an insurance/warantee scam. With the knowledge I got from I diagnosed/repaired my CPS issue for less than 30 bucks...... FEEL THE LOVE !!!!

Thanks again for getting out the word about the proportioning valve...... GOOD LUCK !!
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  #3  
Old May 5th, 2003, 23:03
bchulett bchulett is offline
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Thanks Bill...

This was an expensive study. Here's my update....


5/2/2003 - DEALER INSTALLED THE FOLLOWING PARTS:
- new Mopar front pads
- new Mopar front rotors
- new Mopar rear shoes
- new Mopar rear drums
- new Mopar rear cylinders
- new Mopar hardware kit

Cost: $1,400
final results: After a few days "braking-in" the new brakes I can absolutely say the proportion valve was the root-cause behind the rear thunk and pedal going to floor with little or no brakes. The brake system is now actuating correctly... medium-to-low speed stops firm... stops almost on a dime. I can feel the fronts/rears engage... and... disengage in proper sequence---can feel the pads/shoes in brake pedal again. Brake pedal stroke improved significantly.... starts engaging approximately .5" after depressing pedal. Rear thunk essentially gone... almost like when it was new. Concerns still exist regarding high speed stops... ability to lock all four 31's. Haven't really stood on the brakes yet... don't want to glaze'm.

Conclusions/assumptions:
- 114K miles without changing calipers or cylinders.
- 3-4 front brake jobs pushing pistons back.
- 1 rear brake job pushing cylinders back.
- proportion (combo) valve contaminated, changed bias & front/rear actuation.
- possible PV damage due to multiple pressure flushes/bleeds with contaminated system.
- lack of pressure to rear brakes, unable to self-adjust in reverse.
- front pads/rotors overworked, possibly became glazed.


Future mods/tests:
- new Stainless-Steel flex lines


Open to feedback on cause and effect.

Bob H.
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  #4  
Old May 6th, 2003, 08:06
ChEwBaCcA ChEwBaCcA is offline
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Heres some tips
front calipers =$13 each rebuilt @ autozone/ Murrys etc after you give up your cores
Do it yourself and save huge cash... You can get Big Raybestos drums for $60 the heavy and HQ style brand new.

I have never had good luck pushing pistons back in....seems when they come out for 2x they loose something..

Most techs I have talked to just swap in rebuilt calipers to prevent headaches after the repair.

Chewy
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  #5  
Old September 24th, 2003, 21:02
bchulett bchulett is offline
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Quote:
Originally posted by bchulett

Future mods/tests:
- new Stainless-Steel flex lines
For what's it's worth ....

As an update to my study to try and find the root-cause for poor braking issues on pre-95 XJ's (without ABS) ...

After 151K miles ... I just had the old brake lines replaced with SS lines. As a result, my braking power, pedal action & firm feel has improved significantly and is now the same, if not better, when I purchased my 91XJ new---and this is with 31"x10.5"x15" tires.

This is using all 1991 OEM components except the SS lines. My assumption is new OEM rubber lines would have performed close to the aftermarket SS components.

It's nice to have good brakes again ... and I don't think it's absolutely necessary to alter the original design to remedy the situation.

RH
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  #6  
Old September 25th, 2003, 14:00
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edboyce1971 edboyce1971 is offline
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Which Prop valve?

Maybe I missed it...whaich new valve did you put in? An OEM or something off of another year or an aftermarket? If you already sid I'm sorry for being stupid.

Ed
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  #7  
Old September 25th, 2003, 14:55
bchulett bchulett is offline
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Re: Which Prop valve?

Quote:
Originally posted by edboyce
Maybe I missed it...whaich new valve did you put in? An OEM or something off of another year or an aftermarket?
Sorry Ed ...

I realize this thread is somewhat confusing ... but so was my braking problem. I had a new '91 OEM Prop valve installed a few months before my SS flex-lines were installed. In fact, if you read through this thread you'll notice I've replaced every brake component except for the pedal, SS fixed-lines and rear backing plates.

Over that past few years I've been trying like hell to isolate the poor pedal action (firmness) with these brakes. Installing the OEM proportion valve "helped" but didn't bring my brakes completely back to life.

When I really needed brakes they still appeared to flatten out and the pedal felt spongy at the end of the stroke like they had air in the lines or something.

Needless to say the new brake lines did the job as far as bringing new life back to the hydralic system ... wish I would've started with new flex-lines first.

Now... they work like they did in '91 and I can stand on the brakes with confidence again.

RH
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  #8  
Old September 25th, 2003, 15:25
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edboyce1971 edboyce1971 is offline
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start with the lines?

So if I am following your reply correctly you would have started with the new lines? When I read your summary it seemed like the prop valve really made a big diff. My brakes have that "spongy" feel at the bottom as well and I think it is probably the lines. Thanks for your write up....sorry you had to flush all that money but I'll bet a bunch of people will save some jack because of it.

Ed
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  #9  
Old September 25th, 2003, 21:19
bchulett bchulett is offline
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Assuming your basic components are in good condition including pads, calipers, rotors, shoes, cylinders & hardware .... and if they're still soft after bleeding & adjusting the rear shoes/parking brake .... yes, I highly recommend changing the flex lines first.

I had last brake job performed by a dealer ... the same one that installed my prop valve----I had them install the valve and bleed the system... then I test drove. It appeared to show improvement.

Then I had them perform complete brake job and it definitely was better----keep in mind this is freshly bled & adjusted. But after driving it a few months it still seemed weak at the bottom of the stroke.

I guess if I knew what I know now I would start replacing these parts in reverse order ...

1. Basic components
2. Flex Lines
3. then all other hardware: prop valve, MC, and booster ... and, if you're forced to come this far it's probably a better investment to upgrade to the later model components.

BTW: I took my old prop valve apart ... I couldn't find any clogged orifices. With all the money I put into this thing chasing this problem I could have installed rear discs and used Brembo or Wilwood components.

Even the so-called brake experts didn't know what to do.
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  #10  
Old September 25th, 2003, 22:17
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DaveWV DaveWV is offline
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Something I do now after I was told to, was while pushing the caliper piston back in while doing a brake job, open the the bleeder valve and let the fluid out that way. Apparently pushing fluid back through the system is not nice to a few parts like prop. valves and master cylinders.
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  #11  
Old November 20th, 2003, 13:33
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pancake pancake is offline
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Quote:
Originally posted by DaveWV
Something I do now after I was told to, was while pushing the caliper piston back in while doing a brake job, open the the bleeder valve and let the fluid out that way. Apparently pushing fluid back through the system is not nice to a few parts like prop. valves and master cylinders.
Yup...pressure has to go somewhere right?
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  #12  
Old November 21st, 2003, 01:46
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Wayne Sihler Wayne Sihler is offline
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I may have missed this in all the work you had done,but did you have the system flushed ?
What I,m talking about is a total vacumn bleed of the brake fluid.Did this on my 96 several years ago,used 2 qts of fresh synthetic brake fluid.
The dark fluid and related crap in the system were a shock to see.
Wayne
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  #13  
Old November 21st, 2003, 09:18
bchulett bchulett is offline
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Wayne,

All this experimentation and work took place over a 2-3 year period.

As yes, every time I changed component(s), I had the system flushed ... $60 each time. I didn't mention that because it's always been a SOP in my book.

Sometimes I thought pressure flushing-beeding is what was causing the problems ... due to the potential risk of sending particles through the entire hydraulic system ... and getting lodged in the P-valve or other places.

I don't know if this is a good practice with hydraulics ...

Maybe a mechanical engineer can answer this ?
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  #14  
Old November 9th, 2005, 22:15
Piece-by-piece Piece-by-piece is offline
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Re: Got Brakes? (Define "Brakes")

Thank you for your candidness. I thought I was the only one having these retarded brake problems! Replaced most rear brake parts already; will try the proportioning valve next...
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