I will be rebuilding the right front caliper on a '84 Euro TD wagon (Ate) and assume it will be very difficult to reseat new seals, heat shields, dust boots, etc without splitting the caliper apart. Many advise against this, why? Very curious and I need just the facts Ma'am -thanks!

Successful "ReMating" of the Two Halves [Pressure and Leak-Proof] gives
Whole New Meanings to the term "Difficult".

ALSO,the cost/benefit ratio just ain't there...
Quality European rebuilds are So inexpensive.

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'84 300SD sold
124.128

done many ATE with no problems ~~~ since you didn't mention why you are rebuilding, i'm assuming that the piston is frozen ?? and assuming this is a single piston caliper

if frozen ~~~ remove caliper mounting bolts and pads, leave brake hose connected ~~~ slide in a used brake pad and use brake pedal (hydraulic pressure) to push piston out ~~~ cover caliper with a rag to contain brake fluid splatter ~~~ if piston moves and bottoms out on brake pad, remove pad and replace with something thinner to allow the piston to come all the way out ~~~ IF THE PISTON DOESN'T MOVE, REPLACE CALIPER

with the piston out, remove brake hose at caliper and place on bench ~~~ remove the 4 bolts and split caliper ~~~ do not lose or damage the 2 sealing o-rings, they are not available ~~~ clean passages with brake kleen and using emery cloth clean the piston bore and the piston ~~~ blow dry ~~~ replace piston o-ring in bore and coat with clean brake fluid ~~~ replace piston, also coated with brake fluid, should be able to compress in bore by hand, install boot and clamping ring ~~~ coat caliper half o-rings and torque the 4 bolts ~~~ mount on car with pads and bleed

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1989 300ce smoke silver / brazil, in a constant state of flux ~~~

Ive heard the same thing about not taking them apart for years, and for the life of me, after taking front and rear calipers apart and rebuilding them on all the MBs Ive ever owned, I still can't tell you why the concept of splitting them is such a big deal!

We are talking about two machined flat surfaces with one or more fluid passages that need O-rings which are usually provided in the rebuild kits ive got in the past. If not, you can replace the O-ring from about any hardware or automotive store in the world. There is even a cup to place the O-ring, and you just bolt them back together making sure they are oriented correctly and even. If you are worried about that, mark the orientation for any slight play, but they typically have 4 tightly fitted bolts, so thats unlikely.

The one thing I would not do is mix and match caliper halves as they are probably machined to specification with eachother, maybe thats where the worry comes from. Do one at a time.

With all the other things people do to their cars on a daily basis, splitting the brake calipers I would put at a #1 on the difficulty scale, about as easy and safe as replacing a fuse.

Much harder is pulling the piston out, and replacing the square cut seal. A caliper piston removal tool really helps in that circumstance, and rust makes it pretty difficult. Several times I had to give up and ended up getting a new caliper. Its amazing what you can bring back from the dead though! If you can get the piston out of the bore, and its not rusted out inside there, theres a good chance you can bring that caliper back into service!
I usually get the rebuild kits from MB for about 50-60 bucks after I know the caliper can be rebuilt.

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As long as the o-ring is rated for contact w/brake fluid. A normal rubber o-ring will swell up and break apart with brake fluid contact.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Remember, the FSM says do not split them...

but the trick if all else fails it to mount them very securely and protect the distance from the caliper the piston can travel... ( or ricochet )
and use air power into the bleeder hole....

Very dangerous if you do not do it correctly !!!!!!!!

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I just replaced my master cylinder and the brakes are now fine. I did nothing to the booster other than to make sure there was no fluid in it. I know there is some controversy whether a sinking pedal is the MC or the booster, but in my case a new master cylinder solved the problem.

I cannot argue with the quote from the FSM.

It is just that Rebuilt Calipers bought at a Auto Parts store are taken apart by someone; and someone puts them back together and they sell them.
So I do not see why I cannot be that someone.

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84 300D, 82 Volvo 244Gl Diesel

It will leak. Keep a big jug of DOT4 in the trunk.

Good luck though.

Rebuilt calipers are cheap to buy for what they are. Are euro Ate calipers somewhat different from US ones?

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Ben
1987 190d 2.5Turbo

The MB 123 service manual advises against it. 'Nuff said.

Your assumptions with regard to difficulty are overblown.

usually if the piston is completely frozen in the bore, its rust on the exterior side of the piston outside of the square cut seal and rarely any deeper.

If your pistons are frozen, after you have split the caliper apart, using a tool that grips the inside of the piston, you should be able to put enough force on the piston to rotate it out of even a rusty bore. Once thats done, you can assess the level of damage and what needs to be done.

Its usually a fail of the dust cover that allows water to rust the bare metal of the outside of the piston as the brake wears. Since you are replacing the cover, you can take the piston over to a wire wheel and remove any scale or rust from the lip outside of the square cut seal groove and inside of the dust cover groove.

A completely failed and rusted dust cover will be a total PITA to remove from the lip around the piston bore, and you may have to get creative with prying to get it off, the old ones usally have a metal band inside it that rusts to everything and complicates things, or rust has encased and trapped the rubber boot.

the inside surface of the bore may need a touch from a dremel or small mounted wire wheel, and typically thats all it takes. then you can reassemble using nice clean brake fluid to lubricate the piston sliding in, and your new square cut seal. All the other stuff should fit in nicely, but you will probably want to clean all the surfaces with a wire wheel, and I usually put some grease or lube around the dust cover sealing surfaces.

I also paint mine as well, and I have even had a pair powedercoated as an experiment, which look great!

If you do take it apart, if you don't replace the O-rings on the mating surfaces, its definitely true you could start to have a leak. No point in reuisng the originals, its not completely rebuilt if you don't replace those rings.

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This post brought to you by Carl's Jr.

Another method to remove a stuck piston: use a grease gun. On those grease guns with a lever ..... they push the grease out at high pressure .... maybe over 10000 psi , don't remember exactly how much, a lotl

Remove the female nipple on the tip of the grease gun that fits on a zerk fitting, the threads at the end of the out put pipe on the grease gun are the same as the brake fluid input threads on the calipers. So screw it right on to the brake fluid input of the caliper and start pumping. That will put A LOT of force on the piston. I never saw a piston it wouldn't push out.

Its a greasy mess .... you can reduce that mess by filling the caliper with water first. Lots easier to clean up ... and .... incompressable.

Splitting the brake calipers makes it a lot easier, a lot, to do a good rebuild.

My W123 Calipers have 2 postons. When using the grease pressure method what do you do when only one piston comes out leaving the other Piston still stuck?

Of course it is better to have 1/2 of a problem then a whole one.

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84 300D, 82 Volvo 244Gl Diesel

OK.. the original post within a post did not carry into this..

The part which says " rebuilding the right " bothers me...... In forty years of doing stuff myself and reading the instructions and questioning older mechanics I have never seen any indication that it is ok to do anything to ONE SIDE of an axle... everything is both fronts or both backs , etc...never just one or never split lengthwise on the car.. like both right anythings..
It is your car and you can do anything you want with it... I am just posting this for ' our readership'...

It is not just the 123 manual which says not to split them and then put your life and others on the line by using them afterwards... you might get it perfect and it last forever... but many times these warnings come from something like a factory jig being needed to get them put together correctly.. and I do not want brakes systems done anything except totally correct...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I won't say that I disagree with you, but I would say that Ive had enough bad parts come into my hands after being rebuilt that there is no question that I'm doing a better job on my own parts.
To each his own.

Where I work, I would say that one car in 5 has a brake issue of some sort, whether it be leaking calipers, lines, or rust or seisure problems, I specifically stopped riding my bicycle on the street. Less than half of these cars came in for brake issues, and you can't fix what the customer does not wan't you to fix. You can only get them to sign a written statement that says that you warned them about this, and reccomended replacing this or that, and they left with that knowledge.

I totally agree with do both sides if you do one. I have replaced one and rebuilt another in the past. If one side needs it, the other is probably not far behind.

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This post brought to you by Carl's Jr.