Brake hoses or calipers making fluid black?

My Jeep has never had great brakes, and with 33" tires, it's becoming a lot more apparent that I need to do something about it. And along the path of trying to improve my brakes, I've replaced the master cylinder, the rear brake hardware, countless rotors and pads, with little to no improvement.

I've bled the brakes countless times, hoping to get all the air out of the lines, and have even invested in some speed bleeders since my old bleeders were actually letting air in, but to no avail.

All my brake fluid was nice and clear after I flushed out the system until one day I decided to check it, and noticed that the front reservoir's fluid was a dark brown/black while the rear brakes' fluid was nice and goldeny clear like it's supposed to be.

Something's not right. Could my front hoses be deteriorating on the inside to cause this? Could my calipers be all nasty on the inside? What do you fellas think?

Considering the number of rubber seals in the brake system (wheel cylinder piston cups, master cylinder piston seals, brake caliper piston seals) and the hose linings, it's possible you've got something deteriorating and "dissolving" into the brake fluid. I've seen it before.

Change out the parts you haven't changed yet, and "vacuum flush" the system once more (to get any loose crud out.) Empty the master cylinder, clean it out, refill, then vacuum flush - you'll get more crud out that way, and you'll get a larger percentage of the total crud loose in the system.

And do you think this would significantly improve my braking ability?

Chew on it for a minute - if your seals are deteriorating to the point where they're turning up - in tiny bits - in your brake fluid, how well can they be sealing anymore? You may even be losing brake power (by compressing the now-soft seals) without losing fluid or drawing air into the system.

The general rule of thumb is, if you've got to replace one rubber part, just replace all of the rubber parts - no sense in letting yourself in for trouble.

Granted, the early XJ is a bit underbraked to begin with (which is what make the dual diaphragm booster swap so common,) but why buy trouble when you already get plenty for free? Break open the brakes, and you've already got to bleed the whole system - so you may as well do it for a reason, no?

Looks like new front brake calipers and hoses are going to be at the top of the list for this summer. Fun fun fun.

Moisture or water in the system plus heat makes the fluid go black. You can spend about $89 or so on a good pressure bleeder like this. Makes life a bit easier, especially with speed bleeders. http://www.motiveproducts.com/02bleeders.html
Alot of people swear by gravity bleeding too, much slower but it works.
A couple of companies sell colored brake fluid, clear, gold, red, blue so you can see the color change when the new fluid hits the bleeder.

If you've completely flushed the old fluid out, I agree w/ RichP that moisture/ contaimanants would cause the fluid to darken. But I would assume there would have to be a leak in the system for this to happen. Another possibility might be the added stress of the 33's and /or heavy brake use could be overheating the fluid. This can also darken the fluid. Some high temp brake fluid and bigger brakes might be in order. Just a thought... are the rears working properly? Fronts may be doing most of the work if rears aren't adjusted/working...

The front brakes normally do most of the work - 2/3 to 3/4 of it, as I recall. I'd invest more time in keeping the front brakes up to scratch than the rears - although I do service, maintain, and adjust all where necessary.

You'd have a much more drastic difference in brake efficiency in losing the front brakes than you'd have in losing the rears...

I'm pretty sure it's the front brakes that just aren't up to par. The rear has all new hardware and cylinders, pads are about 3k old, drums were re-truned, and they actually lock up when I hit the brakes on gravel. I think the front ight just be letting in a tiny amount of air or water to screw up all the power I can get.

Front brakes perform approx. 70% of the braking force. Its relevant to the weight bias in the vehicle. Yes its very true that you would notice a problem with the fronts more easily, rears have a tendency to wear or become out of adjustment slowly over time- less noticable to the driver, might not even notice the difference because it can happen over time. Just thought it would be worth mentioning from past experience. If the fronts are asked to do 100% of the braking, and then compound the problem with oversize/weight tires and wheels this can add a lot of heat and overwork the system. I think it would be worth it to at least check...just my opinion though...and if it helps, a simple adjustment could be a free fix!!!

There is also another issue, if you do alot of water crossings the hot brake fluid can pull in water thru the seals, the seals are made to keep pressure IN not OUT. If you get your brake cylinders under water or your front calipers and sit there a few minutes this will happen.
This is also common on differentials, sit in water up to the axles and water will get pulled in just by it being cooler and the diff fluid warmer..

See, I've adjusted my rear brakes before and while it does make a significant difference, I'm always afraid of making them too tight... I did that before and ruined a drum and the shoes on that side... luckily it was just a D35 though Does anyone have any tips on how to make sure your drums are adjusted just tight enough without making them rub excessively?

RyleyF said:

See, I've adjusted my rear brakes before and while it does make a significant difference, I'm always afraid of making them too tight... I did that before and ruined a drum and the shoes on that side... luckily it was just a D35 though Does anyone have any tips on how to make sure your drums are adjusted just tight enough without making them rub excessively?

Click to expand...

The only way I know of for sure to cure the drum brake problem is to do a disk conversion.:cheers:

Kyung

just a slight rubbing. You should still be able to turn the wheels with one hand...

And then there's a method of going in reverse with the eBrake on that's in the Jeep's FSM.......that doesn't work all of the time though. Just adjust them until there's some friction but you're able to turn the wheels by hand and such.

Activating self-adjusters require you to alternate between applying the brakes in forward and reverse directions.

The shoes in drum brakes actually shift as they contact the drum, and wedge themselves into the drum. Thats why drum brakes require a lot less hydraulic pressure (pedal pressure) than disc brakes for the same amount of braking force.

The self-adjuster, its star wheel and cable with lever, work by the shifting of the drums tugging on the cable. Obviously, the more out of adjustment on the shoes, the more they'll shift when you apply the brakes. BUT, they stay close to the last spot they shifted, that is why you have to alternate between applying the brake going forward then reverse, repeat, to get the max amount of shift on the shoes, i.e. shift them back and forth within the drum.

The self-adjuster works between the two shoes, what moves the shoes has little to do with it, whether its the e-brake or normal brakes, the shoes still move the same. A preference toward the e-brake, the only thing I can think would be the e-brake would only activate the rear brakes, thus putting more force and motion on the rear brakes and maybe adjust the rear drum more quickly than using the normal service brakes that would share the braking force with the front discs.

Personally I alternate between both e-brake and normal service brakes, as I quickly apply the brakes both forward and reverse several times to adjust the rear drums.

Remember, the e-brake has a cable adjustment as well. You have to have the rear drums well adjusted, and then if the e-brake cable has stretched, you'll need to do the adjustment for the cable as well, to get a good e-brake.

FRONT CALIPERS I have rebuilt several calipers, but never a Jeep, they are surprisingly easy. The kit with the seals is extremely cheap. So consider rebuilding them yourself. At the same time, I thought I saw on the www.NAPAONLINE.com website that rebuilt calipers for an XJ were only $18 after your returned your core charge. At that price it is probably worth it, since you should get a nicely cleaned up and repainted caliper, which would save that pain when doing it yourself. For a difference in cost of probably about $10-$15 between buying the rebuilt and DIY, its probably worth it to save yourself the trouble and get a much cleaner and repainted caliper.

I've tried adjusting the eBrake to make it tighter on my XJ but the nut was seized......so I gave up not wanting to snap anything and have 0 ebrake.

Mine was seized also, I applied a propane plumbers torch for about 5 minutes to the nut and it backed right off. Of course the flame melted away the nylon insert for locking the nut, I just got a grade 8 replacement at my local hardware store with a Nylon insert, applied lots of anti-seize to the threads putting on the new nut.

Good idea.

My ebrake works well, just have to pull it higher than I'd like.