rear brakes over adjusting.....

brian · 10-26-09, 06:51 PM

...themselves.
pretty much it.
had issues a few weeks ago.
got home that day and noticed a heavy brake aroma from the rear. looking closer the wheels were quite hot and looking under showed lite whisps of smoke from the drums.
pulled everything apart and other than being to tight everything was in order.
let it cool and reassembled. both sides seemed to be about the same amount of over adjustment.
been fine since then... till today.
i have been in the habit of feeling the driverside rear wheel after either driving to work, or back home....a trip of just over 20 miles. normally only remember to do it once....mostly in the afternoon. this afternoon the DS was just slightly warm. warm enough to get me to check the other side....which was plenty warm...but not hot like the last time.
a tug on the ebrake cable on the axle showed the DS was just a wee bit too tight while the PS was indeed overadjusted a good bit too much.
i could'nt get the star wheel to loosen through the backing plate on the PS, so the drum came off....don't ask how. with the wheel off i could not turn it, yet when i ran two bolt in the threaded holes it literally popped off.
once agian everything looked in order. backed the adjuster off and reassembled.
so for the next however long i'll not use the ebrake as a parking brake, as i have been.

thoughts, or did you quit reading?

2mbb · 10-26-09, 08:13 PM

So when were your brakes last rebuilt? The self adusting arm is supposed to push down on the outboard side of the star wheel. When you pull the e-brake handle, the adjusting lever is pulled up, then spring tension pulls the lever down to adjust the star wheel. I suppose of the star wheels are installed on the wrong sides, then pulling up on the cable may cause the wheel to tighten when the lever pushes up.

to loosen the star wheel from the hole in the backing plate, you need to use two tools. A screw driver to push the adjusting lever away from the star wheel and a brake lever to loosen the wheel.

ohrly? · 10-26-09, 08:43 PM

My rear right brake is adjusted wayy too tight.

I went to stop at a light today and it today locked up squealed like a banshee with every pump. (pavement was dry)

Was stopping at a yellow light, tire totally locked up and I ended turning right at the intersection because i wasnt stopping! (pavement was wet)

So what did I do to solve the problem?

Kept driving and went and bought a new used turbo!

If you can't stop, might as well go faster!

Trapper50cal · 10-27-09, 10:56 AM

Sometimes the phenomenon you are explaining (backs locking up but truck just sliding along) is actually the fronts not working (or not having fluid pressure) and could be the brake master cylinder or the lines by the calipers. Unless I'm misunderstanding what's happening. The fronts have much more to say about stopping the truck as the engine weight is directly above them. W/O the fronts, the truck will just lock up the rear tires and keep sliding forward as if on dirty ice.

Spike Strip · 10-27-09, 11:31 AM

I'm experiencing the same problem, and my truck has been parked a while now 'cuz I haven't had time to get to it.

I'll back off the adjusters (through the backing plate) until both rear wheels spin freely, then I'll pull the e-brake - adjusters will click - until the e-brake handle has about 7 clicks in it. Then testing the rear wheels by hand, there will be the appropriate slight drag.

After a few days of driving, the rear wheels will "self adjust" to the point where they no longer will turn by hand, and truck will no longer roll...

The rear brake assy are put together correctly.

But I never adjusted the ROD that goes into the new T100 Master Cylinder that I installed.

I'm thinking that may be the problem. ??

toomanymachines · 10-27-09, 12:38 PM

I have the same problem on my bj60 left rear over tightens.. i was thinking that it has to do with the e brake. as the other side is seized.
BUT I bent the end of the adjuster that spins the star.. away so that it would not make contact.. still tightens up. I have to loosen the wheels fairly often. Can a person buy a jobber set of internals, or do I need to find a wrecked truck? If I can find the lever that is from the e-brake on the right hand side.. I think that will be the start to solveing my problem
what still puzzles me is that mine should not tighten up anymore as I have bent the adjuster away from the tightener...?? but I still have to loosen it. Twice now it got soo tight that the adjuster rod was bent!

Spike Strip · 10-27-09, 02:29 PM

I wonder if the wheel cylinders could be bad ? But both sides at once ... ?

maxpowerTA · 10-29-09, 10:17 AM

I am having this exact same issue on my friends 87 toyota pickup, I too had to resort to bending the adjuster away from the starwheel and it hasnt happened since. I have gone through and dissasembled/reassembled the brakes exactly as per the service manual, Anyone have any ideas as to whats going on here?

Trapper50cal · 10-29-09, 10:24 AM

It appears it isn't what I was talking about....

Rodroo · 10-31-09, 02:45 PM

Bump

I have the same issue, rear left over adjusts to the point of smoking randomly. Really hoping for a solution here!

Spike Strip · 10-31-09, 03:49 PM

I fiddled with the MC adjuster and it was fine... Gonna take the rear drums off today and see if I can figure something out. The pass rear is solid - Driver's rear is very stiff, but I can move it by hand.

I'll post pix of the rear setup and maybe I'm missing something somebody with better eyes will see, sí?

raydouble · 10-31-09, 04:24 PM

Quote:

Originally Posted by Spike Strip

I wonder if the wheel cylinders could be bad ? But both sides at once ... ?

Quote:

Originally Posted by Spike Strip

new T100 Master Cylinder that I installed.

Maybe those older cylinder seals didn't like all that nice new pressure.

Spike Strip · 10-31-09, 04:46 PM

Wheel cylinders are new-ish, not OE... But they did sit a while during the rebuild...

Anyway, here's some pix: (passenger side -rt-)

Spike Strip · 10-31-09, 04:53 PM

Few more:

(Pardon the webs - like I said, sitting a bit)

Spike Strip · 10-31-09, 05:36 PM

Doing a little searching, I came across a thread that said it was the spring in the wheel cylinder... What do you think?

60wag · 10-31-09, 07:10 PM

My 60 did this for a while - there might even be an old thread describing it. I went through the complete assembly and found that they were put together correctly. Both drums were "in spec" for diameter but not by much. Out of frustration, I swapped the drums and the problem disappeared. I never figured out the exact cause but I bet a newer drum with less wear might solve it.

Butt Ugly Chuck · 11-01-09, 04:41 AM

Quote:

Originally Posted by Spike Strip

Few more:

(Pardon the webs - like I said, sitting a bit)

My brakes work great and it's been a couple months since I had mine apart. But thinking out loud here for a possible solution to this thread....

Looking at the adjustable stop on the bell crank assembly pictured above.... What if one were to adjust that further in? Assuming you could do so without compromising performance of the brake (I don't have mine apart to experiment and confirm), wouldn't that serve to 'limit' travel of the self adjuster by reducing the throw of the bell crank arm?

Butt

2mbb · 11-01-09, 08:25 AM

here's another idea. Maybe the springs that hold the brake shoes in are weak or stretched allowing the adjusting mechanism to push the brakes out too far. Every time you pull the hand brake, the adjusting lever rotates up. What stops it from turning the star wheel when the brakes are already tight enough? maybe it's the spring tension.

AC Delco sells a kit they call a 'self adjusting repair kit'. It's essentally all the springs and small parts that hold the shoes on. It's less than $20 at rockauto

Spike Strip · 11-01-09, 10:23 AM

Yeah, I think I'm gonna start small and replace things and see what happens, since there doesn't seem to be a consensus on what might be causing this, and Inspection, yesterday, showed nothing (that I could tell) was wrong with the brake set up. Parts installed correctly. Adj on correct side. Everything lubed and moving smoothly. I did not measure the drums, though.

Quite a few others have had this issue, but all the other threads peter-out without a fix or have a random hail-Mary fix.

So, first, as 2mbb suggests, will be the hardware kit. Since I have a MAF set I bought a year ago, that will now go in.

And while apart I will clean and lube the adjusters, check the drums, maybe even have them turned, and check the FSM on the Bell-crank to see, as BUC indicates, if there's any adj possible there.

If the over-adj still happens, I'll prolly go next with new Ikuta drums and Aisin Wheel cylinders. (OEMs) as was 60wag's fix.

Small tip here: Get yourself a couple of 2.5 in 8mm x 1.25 10.8 grade, fully threaded bolts to thread through the drums and push them off. Really cuts down the frustration level of repeatedly removing drums.

Will post results.

I hate threads without an ending.

Butt Ugly Chuck · 11-01-09, 10:40 AM

Quote:

Originally Posted by Spike Strip

I hate threads without an ending.

X2! Makes for some frustrating searches.

Quote:

Originally Posted by Spike Strip

And while apart I will clean and lube the adjusters, check the drums, maybe even have them turned, and check the FSM on the Bell-crank to see, as BUC indicates, if there's any adj possible there.

I got a baby version of Adobe so can't cut and past a pic from it, but page BR-52 of the FSM I have delves into adjustment of the bellcrank adjusting bolt.

Butt

brian · 11-01-09, 12:36 PM

Quote:

Originally Posted by 2mbb

here's another idea. Maybe the springs that hold the brake shoes in are weak or stretched allowing the adjusting mechanism to push the brakes out too far. Every time you pull the hand brake, the adjusting lever rotates up. What stops it from turning the star wheel when the brakes are already tight enough? maybe it's the spring tension.

AC Delco sells a kit they call a 'self adjusting repair kit'. It's essentally all the springs and small parts that hold the shoes on. It's less than $20 at rockauto

nope.
just replaced shoes along with all the springs and retainers.
drums are cheap enough but i can't see that being the issue.

Spike Strip · 11-01-09, 12:45 PM

I took the right side apart and noticed the wheel cylinder was a little sticky. Slides around, but gummy. Compressing it was sticky, too.

So gonna get a couple of new Aisin cylinders tomorrow - might as well, while I'm in there. Don't what to have to take this sh!t apart again... so that's all for today.

I've got a new set of shoes, too, so screw it. Just gonna replace everything - clean and lube everything - reuse the drums (they measure good), but switch left to right...

If it still does it, I'll go ahead and replace the drums. At least I'll be half ruling-out things...

If it still does it after that.... DISC BRAKE SWAP !

1911 · 11-01-09, 01:00 PM

Quote:

Originally Posted by Spike Strip

If it still does it after that.... DISC BRAKE SWAP !

Rear disc brake conversion is so worth it - just did my 40 last month when I had to R&R the axle seals anyway, and now it stops way better than I thought this truck ever would. No more pulling to one side, and no more adjusting ever.

Spike Strip · 11-01-09, 01:31 PM

Quote:

Originally Posted by brian

drums are cheap enough but i can't see that being the issue.

Drums are cheap if you don't mind buying Chinese crap. Me, I won't buy Chinese anything for the LC, if I can help it.

So if you want Toyo drums ($140 each) or High-quality Japanese (Ikuta) 'bout $118, it kinda gets up there.

Aisin wheel cylinders are $38 each.

I don't understand how drums could be the issue either, but there's much I don't know about brakes

... So that's why the drums will be the last to go.

goldchaser · 11-01-09, 02:15 PM

I haven't got an answer for the problems you guys are having but i rebuilt my drums over 12 monthe back,aftermarket cylinders,aft drums,and pads,springs and all hardware left original.
Don't discount the drums as useless,if working correctly they are quite good,especially with the auto adjust on the handbrake.
Im happy with mine but as its just come off the road for a overhaul i think i might replace the springs/star wheels etc as well.

Spike Strip · 11-05-09, 03:11 PM

Just an update --

I got a little impatient and just decided to throw money at it and replace everything, 'cuz it was driving me nuts and I want to go camping this Month, and don't feel like taking the stuff apart 3 times.

So... New wheel cylinders and drums and hardware. Notice how the aftermarket Aisin brand wheel cylinders not-so-carefully hide the TEQ symbol...

Japanese drums fit perfectly. I painted them with gloss engine enamel.

Will bleed tomorrow and see how it goes.

Spike Strip · 11-05-09, 03:13 PM

My old girl who always looks over my shoulder to see if I'm doing it right!

ElliottB · 11-05-09, 04:10 PM

Looking good Spike! Hopefully this will do the trick for you.

Spike Strip · 11-06-09, 05:59 PM

Well, I dunno brian... Mine seems to be running alright, now... So I'm back on the road !

If anything, I bet it was the wheel cylinders or hardware... Cylinders on both sides were a bit sticky. Hardware was old.

I took the self-adj mechanisms apart and clean and lubed everything, including the bell-cranks, and adj the cranks per the FSM.

So far so good. Sorry there ain't a definitive fix in this thread.

The Monstrosity, as my wife calls it:

rchalmers3 · 11-06-09, 09:22 PM

Quote:

Originally Posted by Spike Strip

I wonder if the wheel cylinders could be bad ? But both sides at once ... ?

X2. Wheel cylinders with almost stuck pistons can cause this. The return springs cannot overcome the stuck pistons, and are left stretched out, leaving play in the area of the separating rod, which gets automatically adjusted out. So while it looks like the self adjuster is the culprit, it is actually doing its job.

Another idea is a mis-adjusted master cylinder, causing a pressure build up. Cracking the bleeders to release pressure after a drive will confirm or eliminate this as a cause. Adjusting the MC pushrod is a quick adjustment.

Rick