Seasons greeting. I hope you all have a great holiday season.

I noticed when I changed my rear pads on the SDL that the right rear inner pad was sticking. Obviously I need to replace the caliper.

It really took some doing to get it to back off, in order to change the pads. Had to undo the line, hammer, etc...

Anyway, Do I have to replace both rears? I noticed that there is a rebuild kit available. I have never done this type of job... would it be to difficult to rebuild them as a DIY job?

Thanks

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Enough about me, how are you doing?

Rebuilding calipers isn't hard if all you are doing is replaceing the rubber stuff.

One seal, and the dust boot. The only hard parts are getting a stuck piston out and getting the piston back in at the correct orientation.

So a search, I've posted this a couple times. I plan to do a DIY article when I get the 220D running, since I parked it due to leaking rear calipers.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Yes it is quite simple to replace the seals yourself but you may want to check the piston for rust first if it is pitted or anything then just buy some other ones instead. My 83 actually completely ran out of fluid in front before, I stopped with the rear brakes. Good thing I was leaving the house then rather than out running the roads!

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Yes, do not just slap a rebuild kit in without checking the piston(s). You'll just end up with a leak again. I just did my fronts, and had one bad piston. That kept me from taking the cheap route, as I couldn't find a source for pistons.
BTW, anybody know of a source for pistons?(now that it's too late for me)

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

To the best of my knowledge, there is not source of pistons. They are precision manufactured, and both bore and piston are chrome plated. I don't think the manufacturers are going to sell individual parts, way to expensive.

Rebuilt calipers can be chancy, too -- if the bore are machined and new pistons fitted without the proper plating, they corrode and seize. No way to tell just by looking, either.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Finishing off another post.....

Couldn't find rebuilt ones from a local MB shop so I tried a local Auto warehouse called bumper to bumper. 3 floors of car parts.

Anyway, they were 48.00 each with a one year warranty.

The car stops like a sports car now, with no squeaking whatsoever.

Thought I'd share.

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Enough about me, how are you doing?

You might want to consider Autozone for certain parts. In the case of calipers, they come with a lifetime warranty, same for the pads.

Don

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it

I wouldn't use AutoZone unless I KNEW the calipers were NOT bored and oversized pistons fitted -- if not properly plated, the piston will seize sooner or later.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

When I tore the one caliper apart, there definately wasn't any chrome plating on the piston, and I know what it looks like. So, I'm not so sure about that point. Makes sense that they should be chrome plated for wear, but I'm not convinced they are. My brother worked as a ASE cert'ed mechanic for about ten years, and never heard of such a problem using rebuilt calipers.
So, I used rebuilts. At half the cost of new, I'll take my chances for now. Budget is way too tight for $500 worth of calipers right now. If I have problems again later, I'll choke up the $$.
BTW, the car stops on a dime now. I about went thru the windshield the first time I hit the brakes from about 30mph

__________________
past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

I'd be very surprised if the bore was chrome plated. Cast iron is extremely difficult to chrome plate. The piston is a different matter. They often are chrome plated.

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95 E320 Cabriolet, 169K

I have no idea what process they are using, however a national chain like Autozone can't supply a lifetime warrany on junk. While the rebuilder might in the end need to replace the part, the cost of handling and the paperwork that goes with it is to high.

My wife had an Escalade which ate pads like crazy. They gave me 4 sets in 2 years, no issues, no questions, no nothing. They were Performance Friction Carbon pads.

In my case I will go with them and if they need to be replaced every 6 months....well I guess I will have clean brake fluid and shiny calipers year after year......after year.

Don

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it

rickg,

If you took your caliper apart and the bore of the cylinder and the piston outside diameter were not plated, you probably have a defective goods claim. Without chrome or other hard plating these surfaces would last a few weeks or months, not tens of years. The rubber boot is nice for keeping lots of junk off the piston as it extends, but a raw piece of steel would rust and sieze in very short order as these seals are not leak proof. So, if the surfaces were not rusty and pitted, they were plated with something like chrome.

In order for the brake to work, and specifically to release after the pedal is released, the square cross section sealing ring must fit precisely as this item and its coefficient of friction with the piston are the only means for pulling the pad away from the disc. To enable this to work the L/D ratio of the piston and the clearance to the caliper bore are precisely matched for each set of parts. If this is not the case, the problem you will encounter most often is the brake fails to release and you get a "stuck" caliper. The next most probable sign is leakage, but this requires a much more significant mismatch, or some corrosion.

So, the seals can only be replaced if the working surfaces of the caliper bore and the piston outside diameter are pristine. If you see pitting or an accumulation of corrosion products, the seal will quickly degrade and no longer perform the function of sticking to the piston, deforming and storing some energy when you apply the brake, then, when the brake is released, as the seal returns to its rest position, dragging the piston back enough to eliminate the pressure contact between the pad and the disc.

When brakes are rebuilt, the parts need to be cleaned up to good surfaces and then re-chrome plated and remanufactured. This process involves matching the remanufactured pistons to remanufactured caliper bores. Since the starting condition is less predictable than with new parts, the outcomes are somewhat less predictable and you end up needing a broader range of chrome plating thicknesses. This can cause problems with the long term life of the plating, but should not be a technical liability to braking performance.

But raw steel parts do not belong on critical surfaces exposed to water, road salt, carbon deposits from burned brake pads and high temperatures. Hope this helps, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Good stuff. Thanks Jim.
That's what happened to my old calipers. They were both leaking and sticking big time. When I pulled the worst one off, and took it apart, the piston was pitted.
I guess that's why no one will sell just the pistons, and why rebuilts are so expensive. My fronts were something like $110/each, with a $50 core charge. You'd think they were gold plated
So, if they actually are chrome plated, it must be a different flavor chrome from what I've usually seen. I've worked as a machinist for years, and any chrome I've seen looks like the chrome on a bumper. This must be more like a satin nickle based chrome or something. The piston had no vestige of bright silver looking plating on it.
Learn something new all the time

__________________
past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

Jim, are you sure the caliper bores are chrome plated? I have yet to see a caliper or wheel cylinder manufactured with chrome plate in the bore. Manufacturers have been producing cast iron bores for decades and car owners have learned to live with its shortcomings. Not only is it difficult - if not impossible - to successfully plate cast iron, it's difficult to selectively plate the bore.

Perhaps the bores are sleeved?... a completely different process. Sleeving is common practice for restoring antique calipers/wheel cylinders and popular for restoring early Corvette Sting Ray calipers.

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95 E320 Cabriolet, 169K

The bore of my (bendix) calipers looked consistently dull, I thought it was just cast. As for the piston it seemed to have some chrome on it, I mean it isn't what I'd compare to a new shiny bumper but more like a hydraulic shaft that has been worked for a while. I'd think these pistons are coated with nearly the same thing as those shafts are.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k