brake boost problems

[toebee97]

I searched for this issue thinking someone else had to have had it, but no dice. So my apologies if this had been addressed in another thread.

My 90 limited has the hydraulic brake boost system instead of the vacuum booster. It's part of a series of recall repairs I think, but I have no idea which parts were installed or replaced. The brakes work, but without boost, so obviously driving it is out of the question. Changing shoes and rotors is one thing, but booster stuff is beyond my level of expertise. I've had a couple shops look at it, and the last one said that the pump controller alone would cost me over $1000 if it needed to be replaced, on top of a $90/hr rate. I also called my local Jeep dealership to see if the parts were covered by the recall warranty(some recall repairs have a lifetime warranty), and they wanted to charge me 79$ just to look at it! And they can't even tell me if the contoller pump or any of the other parts are covered or not!

So my question is this- Are these brake system components easy to find in scrapyards, or are they usually the first thing stripped out of a wrecked xj? Or is this something I should get new parts to fix instead of cheaping out on junkyard parts? If so, where can I get the parts I need for a reasonable price(I work for minimum wage, so the cheaper the better)? Also, is this a hugely difficult think to do for a guy with moderate experience with a wrench? I have access to a small shop and a decent amount of tools. Anyway I'll start with that, and if anyone has additional questions then fire away, I need all the help I can get!

[xj4life2]

The abs pump is a lifetime replacement from Chrysler. They will try to hit you up for the accumulator $185.00. The pump new is $1400.00 last time I checked. Before you do all this though, check the abs fuses (there are 2) and the abs relay. these are normally the issue but I have had my pump go out. I would advise against the use of JY renix parts. If your gonna replace everything.... scrap the renix and go to a newer yr with a conventional system. Oh and by the way if you pay the dealership and it is a covered part they have to waive the charge to diagnose it. If you look on line you can find a list of all parts covered as this was a Federal Saftey recall issued by the Goverment. As a side note most shops do not know enough about the Renix system to work on it.Lastly if you have the dealership look at it and it is the pump be prepared to wait, each one is made to order and it is done in germany to them 4 week to get mine in.

sorry for jumpimg ahead of our resident renix guru but i own one of these lol lol

[toebee97]

I haven't checked the relay, but I checked the fuses, they were absent when I got it, so I put 3amps in it, because evidently nobody carries 2amps anymore. The first time I put one it it blew the fuse. Does that mean the relay is bad? After I put another fuse in it, it didn't blow, just the first one. Where is the relay? Is that the one on the driver's side that's boxy looking?

Good to know about the dealership waiving the diagnostic fee. I found this after a quick search of recalls, basically looks like the pump motor and pistons have a lifetime warranty even if they've been repaired before. Am I reading that right?

http://www.automotive.com/1990/49/jeep/cherokee/recalls/50959.html

[xj4life2]

if I remember correctly the relay is on the passenger side in the rear of the engine compartment no no its in the master power area under the plastic cover. yes it is a lifetime recall

[W.O.R.P.Offroad]

i have a renix with abs too. im always havein probs with mine. sometimes the pump kicks on and sometimes it dont. when it does the brakes are awesome but when it dont i have no power breaks. everytime i drive it takes like 30 to 45 min of drivin or wheelin before they start workin right or get it way off camber

with just switchin over to the new 8.8 im just goin to get rid of all the renix abs bs thats on there. only good side to it is that the brakes work really good (when they work) even with the vehicle off

[toebee97]

Forgive my ignorance, I'm still a greenhorn when it comes to xjs... is the 8.8 a newer and better hydraulic system or a vacuum setup? Is it expensive or a pain in the arse to do? Can you just pull the all the electronics for the abs setup out(speed sensors, relays, etc) or what? If you know where i could read a how-to with some pictures?

[xj4life2]

Forgive my ignorance, I'm still a greenhorn when it comes to xjs... is the 8.8 a newer and better hydraulic system or a vacuum setup? Is it expensive or a pain in the arse to do? Can you just pull the all the electronics for the abs setup out(speed sensors, relays, etc) or what? If you know where i could read a how-to with some pictures?

The 8.8 is a ford rear end that is a very common swap in Jeeps not just the XJ. You do not need to do the swap to convert to a non abs system. It is a stronger axle than the Dana35 you have and if you can find one can come with disc brakes. As for the swap its not bad but you must know how to weld and understand angles ect ect. You can find hundreds of write up on NAXJ and probably here also just do a search for the 8.8 swap. When you do the swap to an 8.8 you have to eliminate the abs as there are no sensors in the 8.8 for the abs to work off of. However as I said you do not need to do a swap to eliminate the ABS just find a donor XJ remove all brake parts, master cylander/booster lines metal and rubber, prop. valve (if needed) go home remove all renix brake system and install the donor system. Yes its alot of work and you will have to do some fab work. But has been done many times. Again search the internet and you will find several articles on how and even the best donor XJ's for the swap.

[toebee97]

It's starting to look like Payless 4x was on the money. My mechanic buddy and I took a look at it and did some simple voltage tests on the relay, that's when we noticed it had a ton of corrosion inside it, and it was partially melted. He got the pump to come on though, so at least it's not that. So it looks like it's just going to be a cheap relay replacement, and I should get it back this week. If it turns out that wasn't the problem I'll post back, but otherwise thanks for the help! Next up will be a cheap lift!:woot:

[xj4life2]

Glad it worked out for ya, let me mention something mine did recently. Got up on a cold morning 19* and started the jeep with no issues and the abs light was on, figureing it would go off as it sometimes does I left to take the littles to school well after a few minutes of driving its still on and the brakes are fadeing (used all the reserve in the booster) Hmmm I stop by my freinds shop before I go off the hill (30 min all downhill with twisty's) and we do some checking and find my relay had gotten wet and frozen!! after tossing in a new one all was fine. In my 35yrs of working on cars I have never had a relay freeze so thats one to remeber!!

[xj4life2]

It's starting to look like Payless 4x was on the money. My mechanic buddy and I took a look at it and did some simple voltage tests on the relay, that's when we noticed it had a ton of corrosion inside it, and it was partially melted. He got the pump to come on though, so at least it's not that. So it looks like it's just going to be a cheap relay replacement, and I should get it back this week. If it turns out that wasn't the problem I'll post back, but otherwise thanks for the help! Next up will be a cheap lift!:woot:

Give me a call when your ready and I'll get you a quote !!!

[W.O.R.P.Offroad]

i have swapped out the relay with others on my jeep still does the same thing. sometimes it will work find and other take like almost a hour of drivin before it kicks in. today it started up and was workin right off the bat. the odd thing is when mines not workin right i can usually get way off camber and it will start workin.

[BlueXJ]

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Give me a call when your ready and I'll get you a quote !!!

I can vouch for Payless as a standup vendor. Good prices and great customer service.

[xj4life2]

i have swapped out the relay with others on my jeep still does the same thing. sometimes it will work find and other take like almost a hour of drivin before it kicks in. today it started up and was workin right off the bat. the odd thing is when mines not workin right i can usually get way off camber and it will start workin.

I would try bleeding the ABS system itself, then the brakes sounds like it might be a fluid issue. I would also check all the powers and grounds on the system.

[toebee97]

So we got the relay replaced, and added an in-line fuse. Started it up, pedal felt a bit better. But once I started backing down the driveway, I realized there was still no boost. So my question is this: Since it was driven with no boost built up in the accumulator(presumably) for quite a while, is it going to need to be running for a long time until the boost is built back up? Or does it not work like that? Also, if I remember correctly, when checking the running pump with a fluke meter it was running a little lean on power, is it possible that the pump is bad even if it's running?

[W.O.R.P.Offroad]

im tired of messin and dealin with mine. im just goin to swap out to the grand cherokee stuff anyways

[xj4life2]

So we got the relay replaced, and added an in-line fuse. Started it up, pedal felt a bit better. But once I started backing down the driveway, I realized there was still no boost. So my question is this: Since it was driven with no boost built up in the accumulator(presumably) for quite a while, is it going to need to be running for a long time until the boost is built back up? Or does it not work like that? Also, if I remember correctly, when checking the running pump with a fluke meter it was running a little lean on power, is it possible that the pump is bad even if it's running?

Next step would be to bleed the system start with the ABS itself then the brakes be sure to switch the key off and on during bleeding the brakes to keep the pressure up. yes it will take time to build up the 2500lbs in the boost but it souldn't take that long. Is the pump running all the time? Or is it cycleing on and off ? If its that low it should run all the time untill it has the pressure it needs. Is your ABS light on ? Also whats the condition of the rear shoes ? if they are not adjusted correctly it will feel like the brakes arn't working that well.

[toebee97]

im tired of messin and dealin with mine. im just goin to swap out to the grand cherokee stuff anyways
I definitely want to see pics of that. If mine keeps being a hassle I may consider that.

[toebee97]

Next step would be to bleed the system start with the ABS itself then the brakes be sure to switch the key off and on during bleeding the brakes to keep the pressure up. yes it will take time to build up the 2500lbs in the boost but it souldn't take that long. Is the pump running all the time? Or is it cycleing on and off ? If its that low it should run all the time untill it has the pressure it needs. Is your ABS light on ? Also whats the condition of the rear shoes ? if they are not adjusted correctly it will feel like the brakes arn't working that well.
Bleeding the brakes is on my list, I want all the fluids in this thing to be new when I start driving it, I don't want any surprises. I the pump was constantly on, not cycling. And if I remember right the abs light was off. No clue what the rear shoes look like, I'll check that next.

[toebee97]

So after I've done everything you all suggested, and anything else I can think of, this is still an issue for me. For weeks I fought over the phone with Chrysler about the recall till I cussed at them and hung up on them.:sign0055: I think that's what they wanted.

Anyway, I decided to take the plunge and do the vacuum swap. Now from what I've been able to figure out, all I need is the MC/Booster setup with vacuum lines, proportioning valve, and a bunch of new brake lines, right? Anyone want to point me in the right direction here, or even link me to a step-by-step on it?

[toebee97]

...Or not? :confused:

[4.3LXJ]

I haven't personally done this particular swap, but some like it. You will need the vacuum booster with master cylinder as you said with vac booster line, and fitting for the intake manifold. I would reuse all the brake lines. I am not sure, but you may have to reflare the ends. If you do, invest in a good double flare kit and get the right fittings at an auto parts store. This will save you swapping out all the brake lines. Get the proportion valve too. One thing I would also get is the push rod from the brake pedal to the vac canister.

[W.O.R.P.Offroad]

here you go man here is a write up on naxja.org

http://www.naxja.org/forum/showthread.php?t=924285&highlight=brake+booster

sorry i havent replied earlier. i havent looked at this thread in a while.

here is another one
http://www.4x4wire.com/jeep/tech/brakes/xj_wjbrakes03/booster/

[toebee97]

Thanks a ton! I was swimming in a sea of worthless google hits trying to find a write up on it. I found a booster off a Comanche on Craigslist for $20, but I'm kinda leery about it. He says it worked before he started parting it out. I never realized I could use a WJ booster, do you guys recommend using that over the booster from a Comanche? Or is either one an upgrade from this nightmare hydroboost system? Also, one more thing- The abs unit is under the back seat I believe, that whole thing can come out with the pump, correct? Should that kill the abs and brake dummy lights on my dash?

Also, not to be a jerk or anything (lol) but I kinda need to know soon if I should go with a zj/wj booster or not, I'm supposed to meet this guy with the Comanche booster at 5:15pm!

[toebee97]

I decided to just go with the MJ booster/MC for now. It's an upgrade either way, and I already got the parts lined up. I can always upgrade to a WJ booster later. I'll try to take some pictures when I do the swap, since none of the write ups I've seen deal with swapping out a hydroboost setup for a vacuum booster.