Both rear brakes (either the calipers or shoes) seem to be sticking in my '85 300DT. I just attempted to fix this problem by replacing the calipers (one seemed to be stuck), shoes (which were completely worn out), pads, and rear brake hoses. The car drove fine for a few days after the 'attempted fix' but on my way home tonight I experienced what seemed like a loss of power. Both rear wheels were _very_ hot to the touch... seems like I've got sticking brakes again.

I originally didn't blame the emergency brake since I never use it and the shoes were completely worn to rusted metal (my e-brake has never worked... new shoes fixed this). I thought I would have heard scraping/seen worn metal if the shoes were sticking. The first time I had this problem the brakes were smoking and I could smell burning rubber. Now I'm starting to second guess whether it could be the e-brake.

Any suggestions on where to look next? Is there a hose that could collapse and affect both rear brake calipers? Is there any other point in the brake system that would affect both calipers release mechanisms simultaneously? Seeme like a stuck caliper is very unlikely (both are new and both failed at the same time...). Any thoughts on the likelihood of an e-brake problem?

Any suggestions are greatly appreciated... the car is currently stranded at a friends house (where I have only limited access to tools). I don't want to drive any further and risk damage to all the parts I just replaced!

Thanks in advance!
-John

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

U need to pull wheels off. See what is holding it up.
If calipers seized then there should be no play on caliper.
Use a screw driver pry apart the pads see if the wheel free again.
Good idea both wheels jacked up too, then u can turn it more freely.
Could be parking brake, and look at parking br cable too. See if anything cause it to strangulate.

I can't imagine that it's anything in the hydraulic system.

But, you must rule it out.

First, attempt to rotate the wheels, with the vehicle jacked up, and confirm that you are unable to do this. This confirms that something is binding.

Then remove the wheel and crack the bleeder screw. See if any fluid quickly ejects itself. My bet is that it will not. If the hydraulic system is not under any pressure at the caliper, then the hydraulic system is eliminated.

Now check the pads and the emergency brake cables. The problem must be caused by insufficient slack.

Since the 300D uses fixed calipers, instead of floating calipers, there should not be any play in the caliper under normal conditions.

Check the brake pads to make sure they are not binding in the caliper. I have seen defective pads where the friction material was not aligned with the metal backing plate, causing the pad to cock and jam in the caliper.

I seem to remember reading that a stuck e-brake will affect only the forward direction of wheel rotation, not reverse... never did understand why. Perhaps this was related to the mechanism you mention above... reversing the wheel direction would unbind the pads (though this still doesn't explain the situation in e-brakes).

I'll check the pads though it seems unlikely since I have the problem on both wheels and also had the problem before I changed pads.

Will e-brake problems affect both wheels? Are there any rubber hoses that affect the hydraulics in both wheels?

Sorry for all the questions... I'm stuck at my friends house with modem only internet access limiting what I can search (along with my patience ;-)

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

Thanks... I'll try this. Will I need to re-bleed if I crack the bleed valve (assuming no fluid is ejected)?

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

The slight positive pressure in the lines due to the head from the reservoir should cause a slight drip and prevent any air from entering via the bleeder, so, I'm pretty confident that you will be OK.

If fluid is ejected, you will definitely be OK.

If the primary parking brake cable is jammed or too short, both sides will be affected. There is an adjuster under the forward end of the drive shaft. You could loosen the parking brake cable and see if that makes any difference. It's possible that the adjuster lever could be jammed or stuck, also.
There are no flexible hoses that are common to the left and right brakes.

We'll by the next morning the problem no longer existed... drove around for a while trying to get a repeat of the stuck brake problem (no luck). Now I'm playing the waiting game... hopefully it doesn't happen again at an inoportune time. Packing some extra tools in the trunk just in case.

When it happens again I plan on opening the bleed valves (both sides) first... should isolate a hydraulic vs. other problem.

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

Well... on my way home from work last night the rear brakes started to stick again. It had been well over a week since the last episode (daily driving). The pedal felt stiff and I was unable to move forward on flat terrain without really pushing on the accelerator.

I opened the bleed valve on the rear right, got a squirt of fluid out. Opened the rear left... nothing. Probelm solved (temporarily)... drove home from work with no issues at all. I also drove around trying to duplicate the problem by stomping on the brakes, easing into them, etc... no luck.

I think I've got a hydraulic issue affecting both rear brakes. It doesn't seem like there is much else to look at other than the master cylinder. I've replaced both rear hoses and calipers. The only other thing in the rear brake system is the metal lines going to the master cylinder (they combine to a single line). Any chance there could be an issue inside the combined rear brake line? Anything inside the master cylinder that would keep the rear brake system pressurized intermittently?

Needless to say I'm getting frustrated. I've been lucky so far... I'd hate to have a serious brake problem on the highway. I also don't want to replace items without reason (i.e., master cylinder)

Any more tips?

-John

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

You replaced the calipers for no reason why not go for a master cylinder??

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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I replaced the calipers because the first time this happened I kept driving (i know i know...). The brakes were smoking when I got home... the rubber seals in the calipers melted.

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1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon

I don't know how relevant this is, but I have had a motorcycle (BMW) master cylinder fail and cause the brakes to lock. When the fluid heated up it would not "vent" back to the master cylinder and the brakes would slowly lock-up, causing more heat and more expansion until the brakes would fully lock and the brake lever would become very hard with no free play. They would free themselves when they cooled, then do it again after a few miles. I ended up replacing the master cylinder.

I learned 2 lessons:

1. Change brake fluid as recommended because it's cheaper than replacing master cylinders.

2. Do not drive a motorcycle with a semi-locked front brake through sand - don't ask.

two words

master cylinder

I had the exact same happen to me

My brand new calipers failed on a mountain, Sandstone Mtn. to be exact.
Seals melted, rotors warped, pads worn down to nothing.

The master cylinder did it, 20 years old, tested fine but it wasn't in the end. While you're in there check for fluid inside the booster.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

yup... sounds familiar. Looks like I'm getting a new master cylinder. Thanks for the info!

__________________
1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon