I was changing pads and the right side went fine. When I went to the left side and attempted to compress the piston, it shot fluid out of the dust seal and would not retract. (Not sure if that was my fault or not from not giving even pressure to the C-clamp to the piston, but probably.) My question is, these calipers only have 65K miles on them. The right side looks perfect. Do I really need to replace in pairs? I have always heard that you should, but I assumed that meant that you were replacing due to wear and tear on an old set.

I would only replace those that are bad. If the piston is dragging on the other side and does not compress very easily, I would call it bad.

You should replace pad sets by the axle, but I would not go so far as to condemn a good caliper because its cousin died.

Just make sure that you don't mix manufacturers. Bore sizes vary.

That's what i was thinking. Especially since my auto store has the same brand in stock. I don't see a correlation between two calipers on opposite sides of the car and the justification of replacing both just because you are replacing one. My buddy said, "It's hard to explain". Which translates to, "I don't know'.

Your buddy is quoting the age-old addage that brake work should be done in pairs.

As well as the age old addage that, "Beers should be consumed in pairs"

Maybe that explains why I had countless drunken sailors tell me, "But sir, I only had two beers!"

I agree that the calipers should be replaced in pairs as well. You do not want your brake calipers to have uneven wear. I don't have a snazzy explanation, but I like to play it safe. I recently rebuilt all 4 of mine and my wifes calipers and I have been happy with the results.

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1981 240D/297K/4-spd/OM617 (mine)
1982 240D/241K/4-spd (wife's)
1979 240D/291K/4-spd/OM617 (father-in-law's)
1983 300DT/240K/4-spd (brother-in-law's)
1985 300DT/???K/5-spd Intercooler conversion (brother-in-law's)
1985 280TE/160K/5-spd (father-in-law's)
1963 UNIMOG (brother-in-law's)

I also replaced mine in pairs when one leaked. It may not be absolutely required, but brakes are important and calipers are pretty cheap.

And repair kits are even cheaper. In all probablilty, renewing the seals and dust boots is all that is needed.

Everyone always says to replace inpairs. But all I can tell you is that when one of my calipers seized, I replaced it with a good, used one. It was not the same make as what was on it (sorry I forgot the brand. it was either ATE or the other) but everything fit just fine and brakes fine. That was last year and still going strong.

I don't understand the comment about different size pistons or uneven wear on the pad. The piston looked to be the same size.

Also, I have heard that its not worth messing with the repair kit especially if the seizing problem was caused by oxidation pits in the bore. The repair will not last long because those pits are difficult to smooth out.

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the sooner you start... the sooner you'll get done If it ain't broke, don't fix it.. Its always simpler to tell the truth...
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The W123 service manual states that, on a given axle, both calipers must have the same size piston and must be of the same make.

On the W123, the front calipers have 60mm bores, whether Bendix or ATE. The rear pistons are about 22% larger (by area) on the ATE's as opposed to Bendix.

Don't believe everything that you hear.

So all things considered, if I have the same size and brand of caliper, I should be good to go? I agree calipers are cheap, however, when it is one of a hundred more things that need replacing/fixing, it becomes less attractive to do the "might as wells' ".

That is in compliance with the specifications in the MB service manual. There is no requirement in the manual that the calipers have similar time in service.

Thanks Tango, to the parts store I go...