Hello, all!

I've had this postal XJ since about May-ish, and ever since then I've been having the same problem with the rear drum brakes locking up on it... especially after a couple hours of heavy use.

Person I bought it off of apparently just unhooked the fuse/relay to the ABS system so the light wouldn't be on the dash, so I was unaware of it having major ABS problems (not sure if related or not, but figured I'd bring it up). I had that checked out by a local mechanic, and he said I'm getting 0 reading on the back left and an odd reading on the back right speed sensors. He just unhooked all the ABS fuses/relays and pretty much said, "You have standard brakes now." Not sure how trustworthy that is (and I want to fix that fairly soon, but I want this main problem fixed first and foremost).

So, after a bit of heavy stop-and-go between mailboxes (even if I try to take it easy and slow down softly at each), the back drums will begin catching every time I hit the brakes at slower speeds. They usually kick in when I'm decelerating around 5-10 mph, even at relatively soft braking pushes.

Yesterday, I was having to come down a fairly steep gravel driveway, and nothing I tried helped. I tried in drive and neutral, began descent at a crawl, and they still locked the entire time leaving me careening down the entire drive in a slide and praying for my life. My route has one particular road that is nearly 10 miles-long and nothing but gravel and sharp curves, and I have to drive it so slowly that I barely make dispatch each day because if I come up on somebody and have to try to slow down and get off the road it sends me into a near tailspin and out of control. Stopping at certain boxes -- especially those going downhill, even slightly -- results in careful finesse to keep from sliding right into the boxes or going over the hill!

I've spent nearly $3,000 on 4 different shops to look at these brakes and tell me what's wrong. I've had one say, "Oh, the rears were 'out of round," had the one mentioned above say it was the ABS system and said they fixed it by removing the fuses/relays, had one say it could be the rear differential but said he'd have to replace everything for about $3.5k, and actually had a dealership just shrug their shoulders and admit they had no idea. They all tell me the rear brakes themselves look fine, shoes and drums and hardware all look good.

So far, I've taken the proportioning valve off and dismantled/cleaned it, put new pads and calipers on the front in case they just weren't getting the stopping power over the rears, put new rear brake hoses and connector to main line, bled the lines multiple times. I'm out of ideas, and about out of time since the winter time (and Christmas time... ugh) is now upon us.

I desperately need this Jeep to run, as I need it for work and I've already sunk so much into it that I can't start over again right now. Any -- ANY -- ideas or leads on what this could be would be greatly appreciated!

 

 

I hope your doing ok with this jeep. I too own the same model RHD. I have sunk over 9000 dollars into this thus far. But at least I have no car payment. LOL. I can assist you perhaps on anything on this jeep because I have darn near replaced everything.

 

 

A couple of factors about the XJ come together to cause this problem.

1. The tail end of the XJ is extremely light weight. We'll come back to that.
2. The self-adjustment system on the drum brakes is fairly unsophisticated and can be problematic

The rear drum lock-up and low speeds typically comes on right after one or both of the rear drums have "clicked" up a notch on their automatic adjusters. These are cable driven, and are supposed to move the shoes/pads closer to the drum surface as the distance between the pads and drums increases. In my experience, they can go for months without adjusting as they should, but then other times (especially during cold months) they will adjust too often, causing the pads to ride next to the drum too tightly. Causing an overly sensitive braking action that is especially apparent at low speeds. I haven't quite figured out the root cause, but I suspect it might be because the little cable inside the drum is colder and does not stretch as much during the winter causing more frequent adjustments. During the summer months, I often have to manually adjust the pads because the auto adjuster has failed to move the pads out as they wear down.

Some things that can help:
You can pull the wheel and drum, and manually the adjust the adjuster back down. But it may just adjust itself back out in a matter of days as you use the brakes.
The thing that has had the most success for me is to do a long hot stop from speed. For example, when I detect this problem has developed (the one you describe) I will wait until the next time I am on the highway at about 60 (with nobody around) and I will do a couple of long gradual but firm slow-downs where I lean on the brakes relatively solidly. Not trying to skid or anything, but definitely pushing the pads hard into the drum and making sure they generate a lot of heat. Then for some extended period of time things will be fine again.

Now for the weight thing. The XJ is especially prone to rear skidding at slow speeds because there is so little weight on the rear tires, which is made worse by the fact that the front brakes do about 90% of the work on an XJ, which transfers even more weight off the rear and onto the front during stops. So if you are driving around with a mostly empty rear cargo area - consider adding some weight (for example 200 lbs). This will help ensure that the tires stay rolling instead of locking up so easily.

Last but not least, if your current situation is truly bad - you can simply adjust the rear pads out and disable the auto adjusters and drive on the front brakes. Sounds alarming, but many folks with XJs are doing this already without even knowing it. I would prefer having all 4 brakes working, but if the rear brakes are causing safety issues for you, then it would be safer to let the front brakes do the work.

I hope this helps.

 

Have you replaced the slave cylinders? If they are not decompressing quickly enough, then you'll have drag on the shoe-to-drum contact. It seems like they could be slightly stuck pistons in the slave cylinders. They are a very cheap item to replace.

I can't recall reading whether the drum braking hardware was replaced or not. Also, you could just investigate upgrading either the rear axle and brakes or just the brakes from drum to disc brakes.

Ensure that your parking brake/emergency brake cable is correctly tensioned as well once you have the drums removed.

 

My drum brakes get grabby every few months. Nothing to do with ABS, just wear and adjustment of drum brakes and we have a lot of damp and salt. It's a real pain so I want to change to disks but the parts are hard to find over here.

If I were you I'd look up the rear disk conversion kit being sold on this forum. I'd have got one ages ago but the cost of shipping to England was hideous (nothing to do with the seller)

I'd be willing to bet the total cost of the conversion will compare well against the other remedies you've had quotes for, and long term you'll have disks all round and less maintenance.

 

This thread's from 2017. I do hope they got to the bottom of it though.