TXBill, D Norton, and most of all diesel don,

Rebuilding calipers, if there is anything more than a seal change needed, is likely out of the skill range of anyone but a brake specialist. And, unfortunately, most calipers are ignored until, when you take them apart, there is more than a seal to change needed to restore them.

Recognizing when the job turns to replacing several pounds of scrap metal with new parts from changing a few grams of rubber seals, is probably the big judgement call in this task. All I can say here is if there is visible damage, lean toward the scrap and replace decision. But the seal change operation is clearly a job within the skill level of an aware do it yourselfer if all else is in order.

If you look at the Mercedes-Benz shop manuals for the earlier cars (like my 1975 240D) they include caliper rebuilding instructions, which are limited to seal replacements. They involve before and after checks to verify the fix actually fixed the problem, with special tools, and a road test. Most of us do not have access to the special tools, and will rely on the road test. You can do this in stages as well, to reduce the risk. Like check brake function with the system back together in the driveway, then at slow speeds and then at more normal speeds. If this repair fails, it should show up on the driveway test. Leaking fluid, sticking brakes or no brakes (not sure how replacing seals can do this) should show up before you put the wheels back on, with the car jacked up.

The reason you cannot remove metal to correct gouges, scrapes, general corrosion, and so on in the bore, or on the piston, is metal removal, no matter how small, changes the design geometry of the interface between these parts and the seal. Once this is out of the range of the design, which most instructions do not disclose, including the MB shop manual I have, the brake function is compromised. The brake may leak fluid, limiting braking force, or, more likely, it will stick again.

So, if all you are doing is changing a worn out, rubber seal, I think the job can be successfully performed by a reasonably aware do it yourselfer. Knowing the brakes are a safety system, I, diesel don, or any other individual doing the job will take extra care doing the job.

I used to think the brakes were so important I only let the dealer do the brake work. Then I was severely disappointed by sloppy work on something I held so important I did not trust myself to do, and I was forced me to rethink my logic. Confronted by the data, I concluded my brakes are more important to me than they are to anyone else, so I learned how to work on them confidently.

I now only let the dealer or anyone do something on my cars that either requires a special tool that costs as much as the repair itself and is not a regular repair, or is something I aknowledge is beyond my experience and is also not a regular or repeat item. These "rules" still keep my dealer, and a few other mechanics in the area, busy on occasion. As I get older the rules change a little and I will pass a job I used to do to a mechanic just because I do not have a garage anymore and have to work on my driveway, and I don't feel up to the task physically, like in the winter.

Some advice to diesel don for this job, and most of the jobs that expose the insides of machinery, is "Cleanliness is next to Godliness" which was passed on to me by a nuclear submarine machinist with about 40 years on the job. Dirt and the like, known as foriegn material, is the enemy of sliding, precision fits.

So, I do not agree with D Norton's ominous tone, or his blanket statement, but I understand the caution. The kit comes with all the seals and other soft parts you need, and if you limit yourself to taking out the old, keeping things clean, and putting in the new, the job is doable.
If the seals do not fix the problem you will have the same problem when you had when you started, when you think you are done, sticking caliper(s). Unless you make a serious mistake, like leave a part out, you should not have any new problems as a result of changing the seals. In any case all this should be apparent when you test in the driveway. Good Luck, and I hope this helps. Jim

__________________
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)