88 4.0 - just how bad are my brakes supposed to suck?

[4wheelsgood]

I keep reading (and hearing) that the stock brakes on an 88 XJ are poor, especially with things like 31" tires and a 3" lift.

But my brakes just suck, and I have changed everything in the system except the proportioning valve: new master & booster (NOT junkyard, actual new units), all new back hardware, shoes, cylinders and drums, all new front calipers, shoes and rotors. New flex lines in the front, and a new stainless YJ line in the back.

Even with well over $1000 invested in a complete brake rebuild, it still feels like there's no power brakes: I have to stand on the pedal, and if it's a long downgrade the brakes start to heat up and the pedal even sinks if they get hot enough.

What else is there to do? Do I have to upgrade the booster to a later model? And if the brakes are overheating, how much good will it do just to give it a better booster? It seems like these brakes are just not up to the task...?

 

[bcmaxx]

upgrade to a dual diaphram (newer grand cherokee,etc.) search , starboard m has a great write-up! and yes you'll be able to lock up them 31's!

 

[4wheelsgood]

upgrade to a dual diaphram (newer grand cherokee,etc.) search , starboard m has a great write-up! and yes you'll be able to lock up them 31's!

I am planning to do this upgrade, but it doesn't seem that will address the overheating issue that seems to be coming from my front disks... Could my proportioning valve be going out too? It seems like the only thing left to change.

 

[winterbeater]

You're right, more boost on the brakes won't stop the fade. Slotted rotors, different pad materials, adjustable proportioning valve to make the rear work harder. You probably have the best brake fluid already (boils when hot).

 

[bcmaxx]

I am planning to do this upgrade, but it doesn't seem that will address the overheating issue that seems to be coming from my front disks... Could my proportioning valve be going out too? It seems like the only thing left to change.

are they overheating when you are applying them or are they dragging?I messed with the adjuster on the booster push rod, not a good idea. It would be fine until I drove for a bit, then the front discs would overheat.

I live in the mountains,tow and run 33's on stock brakes (other than the booster), never warped a rotor yet.

 

[Shorty]

double/ triple check that your rear shoes are adjusted properly (slight contact with drum) as the fronts alone will give you a hard pedal that you have to "stand" on to stop. The front pads can overheat fairly easily without the assistance of the rear shoes too.

 

[4wheelsgood]

double/ triple check that your rear shoes are adjusted properly (slight contact with drum) as the fronts alone will give you a hard pedal that you have to "stand" on to stop. The front pads can overheat fairly easily without the assistance of the rear shoes too.

Just adjusted the rear shoes to "light contact" setting last weekend. They should still be good. And BTW yes they were much worse when the rears weren't in adjustment. But still pretty sucky.

 

[matttaylor1976]

welcome to the world of 88's. mine absolutly suck! eventually i'll upgrade, but i've learned to leave extra space between me and the guy in front of me. the 31's didn't help matters, but i've learned to deal. it's especially bad with my idle decides to sit a 3k, i usually end up putting the ole' girl in neutral just to get her to stop.

 

[Shorty]

check that both front calipers are free to "slide" on their mounts. If they hang up or get stuck, one pad will be dragging and cause overheating of the front linings and eventual boiling of the fluid (along with accelerated brake wear).

pull each wheel and have someone step on the brake pedal. If everything is working properly, you'll see the piston in the caliper push the inner pad against the rotor and you should see the caliper slide and pull the outer pad against the rotor also. If this occurs, use a small prybar to retract the caliper from the rotor and feel for freedom of movement on each one.


P.S. mine's an "88 as well (on 33's) and even at their best, the ol' AMC/ Ford hybrid brakes suck monkey poop!

 

[4wheelsgood]

Anyone have an opinion about whether a '95 front axle with stock brakes will improve anything? I'm thinking of switching to get rid of the vacuum disconnect, but hoping as an added bonus that my brakes will improve.

I notice there are more options available in terms of aftermarket front rotors and pads for the post-1990 XJs, but I have not compared to see if they are any bigger or if their calipers are any better.

I'm ordering a WJ booster tonight.

 

[Banditt007]

as for brakes over heating, you need two things. good pads and good fluid(within 2 year old dot 4 brake fluid). with the stock brake system if running the correct pads and fluid. you can get the front rotors GLOWING ORANGE and still have brakes. (technically speaking if one was to use race pads). my point is, is that you need better brake pads that can take heat. do some research but for example hawk HPS pads probably would work well for you. they dont work great cold but bite good when they warm up a bit.


lets break this down, since i see people suggesting power brake boosters when you are having a sinking pedal due to pad/fluid over heating...


-larger booster = more touchy power brake feeling... kind of like when you push the pedal down 1" its like w/ the old booster you were pushing it down 2" but this isnt actually making the brake system 'better' more like just a feeling.

-larger master cylinder = higher stiffer pedal so per inch of travel more brake fluid is being displaced... this is done when calipers of larger piston area are used, to get rid of the longer throw mushy pedal feel that will happen all other things staying the same.

-rotors stick with plain faced cheap ass rotors. no difference IMO. people race on autozone valuecraft/duralast rotors. so they will hold up to daily driving no problem. no need for brembo or cross drilled/slotted B.S.

-pads, this is where to spend the loot. you need to research good pads. they are not good just b/c they have 'ceramic' or are 'premium'. you have to find out that they can take HEAT. as a quick reference note anything that is organic will not hold up to high heat, and will fade out faster than a semi metallic pad.

-brake fluid, keep it fresh and changed every 2 years max with dot 4 brake fluid. the reason to change often is it absoarbs water from the air. water having a lower boiling point than brake fluid. so as it gets older the boiling point lowers. this is important b/c when it boils you have water vapor in the brake system...basically air. this compresses instead of being fluid which dosent compress. so basically when u hit the brake pedal this is compressing instead of your calipers on the pads.... no bueno.

technically fading out the brake fluid (boiling it) gives that long mushy 'o shit' brake pedal to the floor feeling.

going over the temp of your pads results in a normal pedal feel except you just keep pressing harder and harder down on the pedal and the truck dosent want to brake harder.

these two types of fade are in general i've felt pads that faded out that also do give a feeling similar to faded fluid.

 

[blondejoncherokee]

my 89 brakes are good, but i had to lube the stuck adjusters on the drums, recently bled the brakes, lubed caliper pins, changed rotors and pads, and replaced all of my hard and soft lines and the proporting valve with a junkyard one, and thoroughly cleaned the hell outta the rear shoes and drums with cleaner and shop towels.
costs about 70 for both rotors, 22 for pads, free prop valve, 12$ for alotta fluid, 45 on longer soft lines from a dakota and a gmc pickup and about 40$ worth of hardline and fittings rented double flaring tool, brake system is good as itll get for now for about 180$ without replacing the master cylinder and booster
i think it would be unwise to not give your lifted jeep on big ol tires a longer braking distance over say a stock veichle, that is give your self alotta space between cars when driving to be safe, thats all i do, and im still planning on rear disks eventually and maybe wj stuff up front, but im gonna take my time with that stuff over the next two years....

 

[JeepTodd]

I had issues with the brakes on my 89 MJ, 90 XJ, 95 XJ, and 00 XJ. All of them had poor brakes. I am currently in the 00 XJ. I am on my second set of Hawk HPS on the least expensinve rotors I could find. I woudl recommend some good high end pads Hawk HPS or LTS (It's supposed to be better than HPS)

I am looking at going to a rear disc conversion to get a bit more braking. I just can't get it slowed enough for my taste.

 

[joe_peters]

I would avoid drilled rotors (cracking) and at the speeds we drive in an XJ there really isn't a need for slotted rotors either. Both of these "treatments" reduce the available surface area of the rotor.

High quality brake pads are a no brainer.

You can upgrade to DOT 5.1, it is non-synthetic and is compatible with DOT 3 and 4, and gives you a higher boiling point.

Stay away from DOT 5, it is synthetic and not compatible with the other fluids or the rubber components in your brake system.

Upgrading to a WJ or 96+ XJ MC and booster seems to give the most bang for the buck.

I have 31s on my 1990, and while I am comfortable with its braking ability, I can't lock the brakes, so I leave a little extra room. That said, I will be upgrading soon because there are times when that extra bit of braking is going to make a real difference.

Last, but by no means least, on those long, down hill grades--grab a lower gear.

 

[cmelo]

I recently did a WJ booster swap to my 90 MJ that had horribly scary brakes. With the booster in the brakes are awesome and it was an easy swap.

 

[4wheelsgood]

For anyone still reading this thread, I finally got around to doing the WJ booster/master cylinder swap, and it was well worth it! Anyone with an old single-stage booster (pre-96?) should do this. It now takes less pedal pressure to stop than my wife's new BMW 3-series.

-OP

 

[big black xj]

Yea, ive always said that aside from the renix to HO cooling system upgrade, this is the second best mod that i have done to my 89.

 

[Ecomike]

For anyone still reading this thread, I finally got around to doing the WJ booster/master cylinder swap, and it was well worth it! Anyone with an old single-stage booster (pre-96?) should do this. It now takes less pedal pressure to stop than my wife's new BMW 3-series.

-OP

My vacuum booster on my 87 Wagoneer died a while back. For now I use both feet to stop fast, and it saves me a trip to the gym for work outs!:laugh3:

 

[Ecomike]

Most aftermarket MCs are just rebuilt, not new. I went through a bunch of rebuilts that killed my vacuum boosters with rear seal leaks. I have gone to brand new, cast iron only, MCs. Don't use aluminum MC's, new or used. I only use DOT 3 now, had bad luck with synthetic.

Other problem areas are the rear adjusters, they need an antisieze lube on the threads for sure. In fact new rear adjusters make a big difference! My old ones had the teeth worn down to almost nothing. New hard ware, springs helps some too. Also check the drums for excess wear. May be time for new ones.

The equalizer can get fouled, and cause trouble for sure. I have an 85,87 and 89, and the 89 has great brakes, the 85 has a new MC and new BB, and it is pretty decent now, even with used pads.

 

[XJSPEED]

I had the same problem and replace all the braking components and it still sucked!!. The best fix I got was taking over to T&J's and let Tom rack his brain on it for almost month and the work alot better. Like everyone else says keep your distance, were driving XJ's not sports cars. Im thinking about doing a rear disk conversion some day hopefully that makes a difference. O yeah I have a 3.5" RE lift with 31's...Mike