Brake Caliper Rebuild

[Kevkeller]

I’ve taken my rear brake calipers apart because they were leaking.  So I’ve cleaned up the cylinders and the pistons. I’ve ordered 2 different sets of seal kits.

Both kit’s piston seals seem pretty tight. I put them in the cylinder and they stick out into the cylinder pretty far. I’ve buffed the piston ends to allow the seal to slip around it easily. However it still doesn’t seem to be enough to get it to slip around the piston.

The first rebuild kit I bought years ago and don’t know if it was specifically for an ATE but the latest was definitely for ATE.

I’m wondering if I’m not getting the correct size or if it just is really hard to get on.

I’m not talking about the water/dirt seal. I’m talking about the round seal that fits inside of the cylinder.

[Cees Klumper]

In my limited experience rebuilding calipers, the seal should be a tight fit, but with some lubricant should fairly easily allow the piston past it. You should not need to really do anything to the piston ends. Can you get the seal around the piston fairly easily when its outside the cylinder? I assume you cleaned the groove inside the cylinder that the seal sits into.

[Kevkeller]

Yes it’s clean. I think if I pre-stretch it it might work. 

[Charles 230SL]

Kevin, I rebuilt both front ATE calipers on my 230 last year and I didn't have any trouble stretching the seals around the pistons. I used FTE repair kits from AutohausAZ. The only thing that stands out in my mind was ensuring the beveled edge of the seal faced the cylinder. I coated the pistons/seals with brake fluid before inserting them into the cylinders - they went in without too much persuasion.
Are you sure you got the right kits for your calipers?   

[Kevkeller]

Well that’s what I’m wondering but that would be twice I got the wrong kits, years apart.
I don’t believe there is a beveled side to the seal but I’ll look closer. I can stretch the seal over the pistons easily however when I install  it in the cylinder seal cutout it stuck out pretty far into the cylinder thus making it hard to slip around the incoming piston.
I did use brake fluid but maybe I’ll use some silicone paste.
Thank you for your thoughts.

[Kevkeller]

I was able to get it in by pre-stretching the seal and I lubricated it with silicone gel.

I see zero reason why it’s a problem splitting the calipers. There’s nothing to it. These rebuild companies want to scare you into using them as far as I’m concerned. There are two small seals that usually come with the rebuild kit.  Then it’s 4 bolts to tighten up.

I used a small hone to clean up the cylinders. I did use the lathe to clean up the rust pitting in the outer seal ring on the piston. This should allow the seal to do a better job keeping water and dirt out. I used a little OSPHO rust converter on the exposed piston area to prevent future rust.

There are replacement pistons available but the ones I’ve seen don’t have the ability to accept the cylinder pin.

The hardest part is installing the outer seal metal ring. I did make a plastic jig to help install it if someone wants to borrow it. I’ll upload a picture later.

[Pinder]

All my brake cylinders were re done on both 68 and 70 280SL from kits from AutohousAZ . all worked with no problems.

[Kevkeller]

I’m making if work but I have to smooth up the bottom of the piston to get the seal to slip around the piston. 
I bought the latest kit from Rock Auto. Maybe that’s why.
The new pistons are on the right. I’ll keep them for the future if needed.

[Charles 230SL]

..The hardest part is installing the outer seal metal ring...

Kevin, glad you got the piston in. Hopefully the second caliper will go smoother. 
yes, I do recall those metal rings being a challenge to press evenly into the piston. Fortunately I had a socket that fit perfectly inside the ring (maybe 27mm(?) and I used a small clamp to press the socket/ring into the piston.  BTW, I used the same clamp and a small block of wood to ease the piston into the cylinder.

[Charles 230SL]

note these were front calipers on my 230sl; obviously a difference between my calipers and rear calipers on a 280.

[Kevkeller]

Yes Charles. My front ones are next. Thank you.

[Benz Dr.]

The caliper with the pin in the bottom are similar to 300SE and rear 600 brakes. Interesting how they work with a spring clip that slides out on the pin as the pads wear. High tech stuff in the day.

[Kevkeller]

I really don’t understand the purpose for the pin other than alignment?  Do you know?

[Benz Dr.]

I really don’t understand the purpose for the pin other than alignment?  Do you know?

Yeah, it has a heavy spring ( not large though ) that  slides over the pin. As the pads wear, the spring will slide outward on the pin. The back of the brake pad has a slot and a thin metal plate that's bonded to the brake pad. The spring assembly has a part that looks a bit like the head on a nail and the brake pad will slide over it. There are other applications beside MB that use this format.
At the bottom of the pin there's a spring disc that bends upward every time you apply the brakes. When you release the brakes the spring disc will retract the pads slightly as it settles back into place.

I'm sure there's more to it than what I remember. It might be in the BBB or earlier MB manuals. 600's have awesome brakes using this pad set up.

[Kevkeller]

Here’s the new cylinder part number from Rock Auto.

[Kevkeller]

I’ve moved onto the front calipers now.  I was hoping to split the front calipers too but I don’t see a rebuild kit with a seal assuming there is one. The cylinders are pretty caked up. I’m assuming I can get them clean without splitting the calipers but it would be a lot easier if they were apart. Does anyone have experience with the taking the front calipers apart? or know where to get a rebuild kit with the seal?

[WRe]

Hi,
I have done it last year with this kit https://www.daparto.de/Teilenummernsuche/FRENKIT/238906?modelId=9310a012.
It's much easier to overhaul the caliper when you take it apart (mounting the dust cover) but not easy because the screws are hard to loose (drive screw)  and harder to tighten.
...WRe

[Leester]

Probably for liability reasons it seems impossible to get those seals from MB. However, Unimog parts are often compatible. There used to be a place in Georgia to get mog parts but I am not finding it now. But there's a place in Denver which I have never used that lists the seals.  https://couchoffroad.com/taxonomy/term/85/all     888-986-4664     If you go to their site and click on brakes, then scroll down you will find them for $2.40 ea.  You might want to contact them and double check to ensure compatibility.   good luck.  Lee
 

[Kevkeller]

Thanks gents.

Do you know if the rear seals are the same size?  I assume they are. 

[mdsalemi]

With a variety of different kits available at differing prices, and containing different parts to achieve a different level of rebuild, I'm wondering if (aside from those who just want to do it themselves for the fun and challenge) there is any reason to rebuild your own calipers.

When my car was restored 20 years ago, I picked up all four calipers, nasty, crusty, dirty, rusty--put them in a box, and took them to a foreign auto parts store local to me in Michigan. My recollection was that it cost about USD $40 each at the time, and they came back looking like new. They've been in ever since. I never bothered to explore "new" at the time, nor did I look for a pre-made rebuilt set and using the existing ones as cores. Of course, there was no way for me to tell if they pulled a rebuilt set off the shelf and gave them to me.

The internet retail thing was fresh back then. We didn't have the large number of online retailers serving the market like we do today. Just looking at RockAuto, they have remanufactured calipers (ATE) for between USD $44-$48, by Cardone and Centric. These reman brands are available in other places, too, such as PartsGeek. Pelican Parts has rebuilt calipers from OP Parts, similarly priced. No doubt there are others out there, but Centric and Cardone seem to show up everywhere.

Aside from the fun and challenge (and the satisfaction of doing it yourself) and the cost of a rebuild kit (see Authentic Classics, $47.30), is there a good reason to do it yourself, when for the same price, ready made and remanufactured units are commonly available?

My calipers are fine, but after 20 years, probably time to swap for rebuilt this summer.

[Kevkeller]

I know that’s an option and I can afford new ones if needed.

I do enjoy rebuilding parts (sometimes to a higher quality) and the satisfaction of a job well done. It’s also nice to see some of my tools pay for themselves. I often learn something about the parts when I do take them apart.

Or I could be out whoring… which might piss off my wife. Lol.

Some prices are ridiculous and I hate getting ripped off.

I’ve seen the Rock Auto calipers. Any idea if they are just ATE rebuilt calipers or a totally different caliper?

One thing I have to consider is shipping to Honolulu. Sometimes my only options are FedEx/UPS and it makes the cost of a part stupid.

[Kevkeller]

And it’s green!

[mdsalemi]

I know that’s an option and I can afford new ones if needed.
I do enjoy rebuilding parts (sometimes to a higher quality) and the satisfaction of a job well done. It’s also nice to see some of my tools pay for themselves. I often learn learn something about the parts when I do take them apart.
Or I could be out whoring… which might piss off my wife. Lol.
Some prices are ridiculous and I hate getting ripped off.
I’ve seen the Rock Auto calipers. Any idea if they are just ATE rebuilt calipers or a totally different caliper?
One thing I have to consider is shipping to Honolulu. Sometimes my only options are FedEx/UPS and it makes the cost of a part stupid.

You are quite literally, KevKeller, an outlier; a data point far out of the norm. That's the price to pay for living on an island in the middle of the Pacific, halfway to Tokyo. Contrary to those geographically challenged, Hawaii are not a few islands off the coast of California. The mail truck can't make it there and darn near everything except your sunshine, rain and pineapples comes in on a plane or ship. Europeans have to worry about VAT and shipping. Most of us in the 48 have it very good indeed. (Note, that the Pagoda World Book you bought last year cost precisely the same amount to ship to you, $4.01 as it did the ones I mailed to the next town over. You got a good deal.)

The rebuilt from Cardone and from Centric, are hardly ridiculous in price; as noted, the rebuilt net of core are less than $50 each. You can spend a lot more having them sleeved by the likes of White Post, like near to $200. New calipers a bit more than that. But with a full rebuild kit from Authentic Classics costing nearly the same as a rebuilt, professionally done...I have no idea who rebuilt mine 20 years ago (just "sent out")  but I'd guess they did an exceptionally good job, as there have been no braking issues in all that time.

The Cardone and Centric from Rock say they are ATE Remanufactured units.

Rebuilt is rebuilt, meaning it's all green. Whether you do it your self of swap your old for a rebuilt, the result is the same. Your core will end up as a rebuilt back on another car.

[Kevkeller]

$50 isn’t ridiculous. I was talking about other parts.

Green was sarcasm.

[Kevkeller]

I picked up some Centric front brake pads from Rock Auto and they were about an 1/8” too thick.  The pistons were all the way in. I ended up shaving them off with my mill to make them fit.
I’d pick another brand.