230SL Brake or Rear End Problem

[ctaylor738]

My 230SL (manual trans, drum brakes in rear, has a problem with what I believe are sticking rear brakes.  I think that it is probably the hoses, but the symptoms are odd enough that I thought I would post it here for opinions.

Start the car after sitting for at 4-5 hours, start to back out of garage, feel some resistance, and then a moderatley loud clunk, and the car starts to move normally.  The longer the car sits, the greater the resistance and the louder the noise.  Applying the parking brake has no effect one way or the other.  The clunk occurs when going forward after sitting.  There are also occasional chattering sounds from the rear end while backing up.

Parking brake works well.  Other than this, the brakes work fine.  Complete fluid flush 10 months ago, fluid is clear.

Yesterday when I parked the car, I let it roll into the garage without using the brakes.  About ten hours later I gave it a shove backwards and got a little resistance, a little noise and movement.  This morning I pushed the car forward, same thing.

So, wondering if anyone else has seen anything like this. I am also wondering how the brakes manage to apply themselves after just sitting.  Or if it's something else.

TIA

[graphic66]

You may have had a shoe come loose from the backing. I had one come "unbonded" and It clunked like yours. The shoe was sliding backward and forward in the drum. Yours may be getting wedged in between the other pad. I actually JB Welded the shoe back on until I got new shoes. It worked great for the short period while I waited for new brake shoes. Those shoes are expensive also.
  Pull your drum and have a look. Easy job.

[ctaylor738]

Sounds like a plan, but will have to wait until next week.  I thiink while I have the car up and wheels off I will go ahead and do the hoses as well.

Thanks for the suggestions.

[xcashewx]

i had the exact same issue.
id put the car in gear after sitting and it wouldnt move. id have to pump the brakes and push the accelerator quite hard. then there would be a clunk and it would move.

i took off my brake drums and found a lot of grease, dirt, and random crap. cleaned all the brakes throughly and now it doesnt do it anymore, it was the brakes. so sounds like this your problem

[ctaylor738]

Haven't been able to work on this probblem, but I continue to go out and give the car a little shove at least once a day.  The amount of force needed to move the car and the clunk when it breaks loose are proportional to the amount of time the car sits.  It's like at least one of the rear brakes gets applied while the car sits.  Very odd.

[al_lieffring]

Chuck

It is very common for the pulleys located at the backing plate where the parking brake cable makes a 90deg bend, to lock up and not allow brake to release.

Another possibility is leaking axle seals, If grease gets on the shoes they become sticky. Just the opposite of what you might expect.

Plugged brake hoses would most likely have the same effect all the time, I found mine to be completly constricted when I checked them. They need to be checked unless you have replaced them.

[glenn]

Chuck, Take the hoses off and run a coat hanger wire thru them. ..      Times are tough---------------

[George Des]

Chuck,

I've had this problem on my 67 230SL. It usually happens when I wash the car  and leave it parked in the garage with the emergency brake set. I'm assuming that it is the pulley's and the cable locking up and I need to get in there with some lubricant. My pulleys, cables and remaining brake hardware including shoes, springs, cylinders, hoses, etc are fairly new.

George Des

[menesesjesse]

Pull the drums off and clean the brakes.  My car sat for a long time and after pulling everything off and cleaning everything up to include the adjusters and backing plate all was good.  The car stops much better now.

[ctaylor738]

Finally got to investigate this today.  Pulled the drums off, no problems with shoes, leakage, corrosion.  I did find some problems on the right side.

1.  The front half of the "guide" (where the pulley lives) that holds the parking brake cable casing is broken so the cable can sort of flop around.

2.  The metal line to the wheel cylinder has a pretty good bend/bash in it

3.  The right side parking brake cable lays on the center muffler.

Not sure if any of this could cause the problem, but they need to be addressed.  While I'm at it, I'll replace the hoses.

Question - is there any sort of hanger that would hold the cable up off the muffler?  I didn't see the remains of anything on the car, and couldn't find anything in the EPC.

[66andBlue]

Hi Chuck,
yes there is a clamp that holds the hand brake cable.  Take a look at the pictures here:
http://www.sl113.org/forums/index.php?topic=9569

[ctaylor738]

Thanks, Alfred.  I finally figured out that the little clip is on the front of the axle piece.  It's there on the car, complete with the remains of the "seal ring."  

Lesson learned.  Next time a search first - no part is too small or obscure for a discussion here.

[ctaylor738]

An update:

A couple of months ago, I replaced the broken right parking brake guide, inspected both sides for broken or binding pieces, put everything back together and adjusted the brakes.  No change, except parking brake hold is better.  I think the broken guide was keeping the right side from being fully applied.  

I also fixed the drooping cable.  

Last weekend I replaced both rear hoses and the crimped metal line on the right side.  I replaced the spring clips where the hoses join the metal lines, so the car sat for a couple of days with the rear hydraulics open since the clips had to be ordered.  During that time, the sticking occurred, same symptoms.  This tells me it's not being caused by the hydraulic system.

With the brakes all back together and bled, guess what - they still stick after sitting, the longer it sits, the more it sticks.  

I have one thing left to try.  I will back off the adjusters at the brakes a bit and see if I can take up the slack at the parking brake handle.  Other than that, I am out of ideas.

[ja17]

Hello Chuck,

The main pivot on the brake shoes can corrode causing this "hinging point" of the shoes to seize or bind. The longer the car sits the worse it becomes.  Check to make sure they are clean and move freely. Using some lube or anti-seize on them is good. Corroded Brake cylinders may not want to return also. Also Check to make sure that the rear shoe brake adjusters are not adjusted too tight. You snug the adjusters up then back them off a bit as I recall?  

I would remove one rear drum at a time and have someone gently push down on the brakes. The shoes will extend outward. Use a large lever or screwdriver to keep the hydraulic piston and shoe from moving too far out. Allow both shoes to extend further than normal but not enough to allow the hydraulic piston to come apart. You can now use the lever to push each shoe back in one at a time and check the movement. Often time just exercising the hydraulics and mechanisms will free everything up. If the hydraulic cylinders are corroded inside you will probably see some leakage after you start using the car

[ctaylor738]

Joe,

I dd inspect, clean, and lube when I did the repair on the guide.  The brakes are adjusted as you correctly suggest.

The problem is not that the rear brakes are not returning, it's that they apply themselves after the car sits without moving.  Today I drove the car.  I parked it in the garage about two hours ago using the brakes to stop.  With hand brake not on, and gearshift in neutral, gave it a little shove backward, then forward.  No sticking.  

I just went out and gave it a little shove forward.  A little resistance/sticking and a gentle "clunk" before it moved.  Then I pushed it back with no resistance or noise.  I am sure if I move it tomorrow, it will take a good push to move it and there will be louder clunk when it breaks free.

[georgem]

Chuck,

You certainly are creating a mystery. with doubt about whether it is the brakes after all the checks you have done,

My thought is that you need to decide one way or the other whether  it is brakes or not, if not move to the next option.

How about next time you do the push test after the car has been sitting for a while, if there is resistance, dont try to overcome it, immediately take off the brake drums .  If each drum comes off easily - you don`t have a brake problem on that wheel, especially if you put the drums back on (and the wheels of course) and try you push test. If the resistance is still there, you definitely don`t have a brake problem.

After that you have to move forward - through the diff then into the prop shaft. Before I started pulling the diff apart, I`d go to the prop shaft and the variuos parts of that. Sometimes sound can travel - so a clunk in the prop shaft could resonate through the drive train and be heard at the wheel station.

So, nothing like a good Sherlock Holmes mystery......one positive is that if the problem isn`t brakes, then yours are now in better condition than when you started - hows that for a "glass half full" outlook?

Good hunting

George

[twistedtree]

It sure sounds like the shoes are sticking to the drum.  That results in the resistance you feel when you start to roll the car, but the roll then un-sticks the shoe and it releases.  I have a couple of thoughts:

Are the shoe and drum surfaces in good shape?  Maybe the drums need to be turned?  A ridge on the drum could be grabbing the shoe.

You might jack up the rear of the car after parking it, then a few hours later grab a wheel and try rotating it.  It might
give you a better feel for what's happening.

Does the bind-up happen only when the car is parked after driving?  I think you said it happens even after not driving.  I'm thinking that if the brakes are adjusted too tight and the car is parked after driving with hot drums, the subsequent shrinking of the drums as they cool could cause binding against the shoes, but this would only make sense if it only happens when parked hot.

Could the wheel cylinders be gummed up and be restricting shoe retraction?  Cleaning the shoe assemblies might not expose (or fix) a binding wheel cylinder.

I guess as a last resort I'd suspect contaminated shoes that are causing sticking and I'd replace the shoes, but I think someone said they are expensive.

Good luck and definitely let us know what you find.  This is a good one.

[waltklatt]

Chuck,
Try letting the car sit for a while and then jack up the entire rear(tires off the ground) without moving the car back and forth. 
They try to rotate the tires to find out which one is sticking(leave in neutral and parking brake off) 
Also put wheel chocks on the fronts to prevent the car from moving.
Use a good jack that goes under the rear axle.
Detective work pays off. 
Is there an reward for the one who finds the problem?
Walter
1967 220SL-diesel
1970 280SL-almost done

[jpsenft]

I had the exact same problem....car would roll into the garage fine, but after a couple of days, same clunking/resistance when starting or even trying to push it out.  One telling symptom was the rear wheels felt warm/hot when I put the vehicle away, like dragging brakes.  As the wheels cooled, the brake drums "shrink" ever so slightly, locking the brake drum to the lining.   My local independent MB specialist pulled both rear wheel cylinders, and had never seen so much corrosion in the cylinders, even after regular bleeding.  Both rear cylinders were replaced, and the vehicle brakes as new.  Could even feel increased brake capability.  Zero clunking/resistance since then.
Jim in Silver Spring, MD

[ctaylor738]

It's now been about three weeks since I replaced the hoses and the somewhat crimped right metal line.  I was working on the front end, so I didn't touch the brakes.  I have been driving the car 2-3 times a week and the problem has almost completely disappeared.   It seemed to gradually get better.  No sticking unless sitting for at least a day, and reduced sticking after longer periods.

This morning I drove it after it had been parked for five days, no sticking or at least none that I could hear or feel.  At a loss to explain this but my theory is that with new hoses and fresh fluid, whatever was sticking, probably in the wheel cylinders, gradually freed up.

I answer to Walt and others.  The drums were never hot after driving, both sides were sticking, and the brakes would re-apply themselves a couple of hours after being un-stuck with a gentle shovee, with everything stone cold.  No combination of applying/not applying the brakes when pulling into the garage or using the parking brake made any difference.

[ctaylor738]

Just to close this out.  The car sat for three weeks while we were travelling.  Moved without even the slightest sticking or noise.

Thanks to all for the suggestions.

[ja17]

Hello Chuck,

I guess you could have had some really wierd situation, possibly a dirt or rust particle  moving around and blocking a fluid hose.  Glad the problem is solved!