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 ~~~

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

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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This post brought to you by Carl's Jr.

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.

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.

For those thinking ' why both sides of an axle ?'
If one is rebuilt and the other is not... the difference in the resistance to brake fluid pressure is enough to cause one side to squeeze on the rotor harder than the other side..... or press against the brake drum ... particularly on the front axle can cause your braking to be ' other than straight line' ... so instead of staying in your lane in an emergency stop you can go into the line of traffic coming towards you ... if on slick roads can cause you to spin out even trying to brake on a level straight road....
Less mechanical excitement or surprise is better with regards to brake response.

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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 rebuilt both rear calipers and debated whether to split the halves. One piston in each caliper was frozen and it was the devil to pay to get them out. I finally decided not to split the halves because of the caution in the FSM. It would have made everything much easier if I had, however.

There is not much room to get your fingers in there for cleaning the bores, but I just took the extra time to do it. It is also difficult to get the dust boot positioned correctly. Again, just took the extra time. BTW, the FSM also cautions against sanding the piston itself. If the chrome is rusted/compromised, the piston is history.

I did have some discoloration that I buffed out on a cloth polishing wheel using emery. Reassembled with surgical cleanliness. Back on the car and the calipers work fine.

Unfortunately, now I have to replace the master cylinder that failed somewhere in the process. The car stops, but the pedal goes slowly to the floor

http://www.peachparts.com/shopforum/showthread.php?t=250621&highlight=floor+booster

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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

first things first ~~~ will the bleed screw move ????

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

To all who responded, thank you! I will rebuild other side too to allow for pressure differences. I have certainly taken on projects more demanding than rebuilding a caliper and at this point, I am tempted to split the caliper for my own education. Does anyone know what size o ring is required if one wishes to renew the o rings when the caliper is split? Thanks again!

I did this about 3-4 weeks ago and there is also another thread from about that time.
It would be best if you had a new square crossection O-ring.

If you look colsely at the area by the O-ring you will see a blue hazy area around it. That is blue Loctite. I guy I worked for taught me that. I works to seal tight fitting surfaces also.

Find the torque for the bolts by looking at the head of the bolt and doing an internet search for the torque.
I found the previous thread:
http://www.peachparts.com/shopforum/showthread.php?t=271499

How can it be that you can rebuild a complete Engine but it is forbidden to take apart your Brake Calipers?
The Rebuilders have to take the Calipers apart to replace the square crossection O-ring.

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84 300D, 82 Volvo 244Gl Diesel