• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Why do Drum Brakes Suck ???

P

Pharaoh XJ

NAXJA Forum User
Location
Cairo, EGYPT
I ve always had a problem stopping my XJ. -Its a 94 no ABS 8.25- It was ok to decelerate on highway speeds but getting it to a full stop was a bit tough in traffic, it dives like hell without stopping, replaced the front pads made it slightly better but not good enough.

I always get dust in my rear fluid lines but not in the front, I get a constant knocking on braking that comes & goes every once & a while.

I decided to do the rear disc conversion, but my dad told me that he had a set of rear cylinder repair kit & new shoes, so after 100k miles I thought probably its time to change the shoes.

I took off the drum cover & the shoes are barely thinner -1mm- than the new ones, so i turned to the cylinders all rubbers & springs are ok no fluid leak everything is tight.

CONCLUSION: Drum brakes are not getting any pressure, thats why they are not used so they never help stopping.

Is there a way to get more pressure to the rear without sacrificing the pressure to the front ?
 
Pharaoh XJ said:
CONCLUSION: Drum brakes are not getting any pressure, thats why they are not used so they never help stopping.

Is there a way to get more pressure to the rear without sacrificing the pressure to the front ?
Click to expand...
Sounds to me like you diagnosed the problem. Dust in your lines means there is no fluid being sent through them therefore no hydraulic action to operate the wheel cylinders and hence no rear brakes. Personally I'd look at the brakelines all the way from the master cylinder to the rear to ensure it wasn't capped off at some point in the past. If they are hooked up as best you can tell, I'd take the proportioning valve apart and clean it and see if that helps. Your master cylinder probably isn't full either if you have a leak in the rear.

I hate drum brakes in general, but swapping to discs to get better rear brakes when there is no fluid in the rear lines won't help your braking AT ALL.

That being said, when I swapped to rear disc brakes I noticed a HUGE difference in braking even without changing the proportioning valve. Discs are also alot easier and quicker to maintain and they dry out alot better than drums.
 
One more thing i forgot to mention I find my brake pedal a bit too hard to operate

kunaji said:
Personally I'd look at the brakelines all the way from the master cylinder to the rear to ensure it wasn't capped off at some point in the past. .
Click to expand...
Its strange because I m not loosing any fluid .

kunaji said:
Discs are also alot easier and quicker to maintain and they dry out alot better than drums.
Click to expand...

Since you swapped to discs do you find it more likly to lock the rear first or scary when braking in a turn ?
 
Last edited:
Pharaoh XJ said:
One more thing i forgot to mention I find my brake pedal a bit too hard to operate


Its strange because I m not using any fluid .



Since you swapped to discs do you find it more likly to lock the rear first or scary when braking in a turn ?
Click to expand...

If you're not losing any fluid it would stand to reason the fluid pressure is not making its way from the MC to the wheel cylinders. Possibly causes would be a bad MC, the proportioning valve sticking or lines being kinked and not allowing the fluid to flow. Dust in the brakelines is not normal and means something is not right.

I drive it like a jeep and not a racecar, but I've not noticed anything scary about the brakes except how much better they seem to stop vs. the drums I had on previously.
 
Crack open a bleeder and step on the pedal, fluid?
if so, you've not got a problem with the hydraulics.
When you say "dust" do you mean rust in the fluid? If so, you need to bleed all of the fluid out, as it's likely never been changed and is full of water.

a much more frequent problem is that the automatic adjusters suck my weewee.
They're probably frozen up, and haven't been adjusting the shoes, so they aren't applying pressure to the drums. When I had drums on the truck, I manually adjusted the adjusters whenever I did an oil change. It's simple, and they always worked OK. The MJ had the larger drum size, but the concept is still the same. Manually adjusting the shoes is the way to go.

Discs however are great, and my stopping power increased, I can lock up all the tires on pavement, previously I could only lock the fronts. It doesn't drive scary, and the fronts are still more likely to lock up than the rear.
 
The dust is not exactly in the lines but its in the MC in the chamber responsible for the rear lines, Its very obvious to see the difference between the two chamber one has clear fluid the other is extremely turbid
 
like little black pieces of rubber?
If that's the case, you may have a stuffed master cylinder, and you're seeing pieces of the o ring in the resovoir.
 
87manche said:
Crack open a bleeder and step on the pedal, fluid?
if so, you've not got a problem with the hydraulics.
When you say "dust" do you mean rust in the fluid? If so, you need to bleed all of the fluid out, as it's likely never been changed and is full of water.

a much more frequent problem is that the automatic adjusters suck my weewee.
They're probably frozen up, and haven't been adjusting the shoes, so they aren't applying pressure to the drums. When I had drums on the truck, I manually adjusted the adjusters whenever I did an oil change. It's simple, and they always worked OK. The MJ had the larger drum size, but the concept is still the same. Manually adjusting the shoes is the way to go.
Click to expand...

Rust is a good point although I have changed the fluid a couple of times. But I heared its dust from the shoe material being captured inside the drum eventualy get inside the lines.

I did adjust the "Automatic Adjusters" manually today but with previous experience they eventualy readjust themsleves hence the AUTOMATIC name. They stay ok for a couple of days then go back to their original state , plus it didnt make that difference.

I just want to point that the when I apply the brakes I can see the system moving means there is pressure getting there but i think just not enough.

One more thing I ve never driven another XJ , but do you find your brake pedal a bit too hard than other cars cause mine feels far from spongy .
 
Self adjusters only work when:
1) You are travelling in reverse, and
2) You use the brakes to stop the vehicle.

Any time I have drums off, when I put it all back together I drive down my street backwards, pumping the brakes all the way. I can feel the pedal coming up as the adjusters work.

87manche told you right. Anytime you see black chunks, or the fluid looks black: That is the rubber components deteriorating. If the system weren't closed to outside contaminants, you would lose fluid.
 
Pharaoh XJ said:
But I heared its dust from the shoe material being captured inside the drum eventualy get inside the lines.
Click to expand...

Not sure where you heard this but it's 100% wrong. The only way you will get dust from the outside into the system is via the reservoirs in the MC. Outside of that, it is a closed system. What you will get is wear on things like the caliper pistons or wheel cylinders, which will cause "crap" to contaminate the fluid. Typically you will see the fluid turn a black color with what looks like very fine metal particles. Also rust in the system due to moisture. Brake fluid is VERY hydroscopic which means it attracts moisture. This is why you are suppose to flush brake fluid every one to two years. I seriously doubt many people do and hence start having braking problems 4+ years down the road.

As for the rear cylinders, you can crack open the bleeders valves and still get fluid out but the piston in the cylinder can be frozen and not applying the brakes. I have had this happen before on an old car I bought. As stated before, if you see “chunks” in the reservoir, most likely that is from the MC. If you are not sure what or how to fix, take it somewhere before you end up killing someone because your brakes don’t work correctly. That’s my .02 worth. YMMV
 
Pharaoh XJ said:
Rust is a good point although I have changed the fluid a couple of times. But I heared its dust from the shoe material being captured inside the drum eventualy get inside the lines.

I did adjust the "Automatic Adjusters" manually today but with previous experience they eventualy readjust themsleves hence the AUTOMATIC name. They stay ok for a couple of days then go back to their original state , plus it didnt make that difference.

I just want to point that the when I apply the brakes I can see the system moving means there is pressure getting there but i think just not enough.

One more thing I ve never driven another XJ , but do you find your brake pedal a bit too hard than other cars cause mine feels far from spongy .
Click to expand...
A few things:
It's impossible for brake shoe dust to get into the sealed system. Otherwise you'd be leaking out fluid.
Yes, I know that they're automatic adjusters, I also said that they suck, and they don't work properly most of the time. The threads get brake dust all over them, the friction stops them from turning like they should. It's a really imperfect sytem, and unless you maintenance them regularly they will seize up.
If the system is moving and you're not getting pressure you've got two possibilities.
The wheel cylinders are hosed or the master is hosed. With your comment about little black bits in the master I'd bet that the master is stuffed, and it's letting the pressure bleed by the o ring.
 
The fluid is just turbid you cant really identify chunks. What do you suggest:
-Bleed the whole system
-Change the Rear rubber hoses
-Change all the lines ( steel + rubber ) ?
 
a bad booster will cause a hard pedal with high braking effort.
 
i find that the rear drums on my 89 work fine when maintenance is done at least once a year and adjusted proporly. drum brakes cant be neglected.

i also did a dual diaphram booster swap and that made all the differnce in the world.

does the 94 have a dual diaphram booster?
 
Pharaoh XJ said:
The fluid is just turbid you cant really identify chunks. What do you suggest:
-Bleed the whole system
-Change the Rear rubber hoses
-Change all the lines ( steel + rubber ) ?
Click to expand...
inspect all the lines.
replace the rear wheel cylinders
bleed system.
Wheel cylinders are cheap enough, About $12 here.
If you still don't get the rear brakes, then the master would be my next suspect if the brake lines look good.
I don't think it's your booster, as you said you have spongy brakes. Spongy brakes says to me that you've got a leaking seal and it's bleeding pressure, or you've got air in the lines somewhere.
A bad booster would end up with a rock hard pedal.
 
I fixed a truck once that had a hard short traveling pedal. There was very little to no fluid coming out the rubber hoses when i took them off the calipers (front) and had someone step on the pedal. The brakes were very ineffective also. Turns out the problem was clogged or blocked rubber hoses. Replaced them and it all worked good again.

Perhaps your rear rubber hose has the same problem keeping the rears from working to there max potential? I would suggest you check all your rubber hoses.
 
89xj said:
i find that the rear drums on my 89 work fine when maintenance is done at least once a year and adjusted proporly. drum brakes cant be neglected.

i also did a dual diaphram booster swap and that made all the differnce in the world.

does the 94 have a dual diaphram booster?
Click to expand...
x2, they need a lot of attention, especially if you hit some water and mud on the trail.

I'm 99%sure it they started that in 95' I know my 96 has the dual
 
You must log in or register to reply here.

Similar threads

M
Need Part Number for Drum Brake Wheel Cylinder Dana 44 Axle
Replies
2
Views
75
Bent
Bent
B
Drum Brake Tip
Replies
7
Views
2K
cruiser54
C
O
Rear Brake Noise Question and Hepl Please
Replies
5
Views
369
asymptonic
A
B
Dash brake light on after replacing rear brakes
Replies
1
Views
1K
RCP Phx
R
A
High pitch whine coming to a stop
Replies
5
Views
3K
chris420
chris420
Back
Top