Front ATE caliper overhaul - pictorial

[WGB]

I have never overhauled a brake caliper before today and so took some pictures if anyone is interested.

I purchased a new left front ATE caliper as mine had the titty for the pad wear sensor broken off and the harness on that side was awol.

I had a spare harness courtesy of the wreck purchased from Nathan (that wreck is still the best $300 ever spent - thanks again Nathan) and as part of the brake overhaul I purchased a new left front caliper, new master cylinder, new flexible hoses and kits for the other three calipers. The booster is away being refurbished.



Some time ago I purchasd a set of "Flare spanners" and they were never more useful than when opening the 11 mm connectors on the brake lines and master cylinder connections. Even with them care had to be taken to hold the spanner level with the fitting but I am sure a regular spanner would have rounded most if not all of the connections.

Once the caliper is removed from the car you need to blow out the pistons with compressed air - they are very tight and will not budge with any other method. They also come out with some ferocity so watch your fingers.



One of the issues is that these calipers are twin piston calipers and invariably one will come out leaving the other still in it's bore. After some mucking about trying to block the other port unsuccessfully I replaced the piston that first  came out just enough so that it sealed it's own port and then held it loosely with a vice grip as shown. Another blast of air and the frozen piston comes out exhuberantly.



The seal needs to be prised from the bore and the bore and piston cleaned of any surface rust or markings.



Here is a cleaned up piston which needs to go back into it's cleaned up particular bore.



Here is the ATE kit as received from Autohausaz.com which also comes with instructions and recommendations for directional fitting of the offset edge of the piston.



I used M-B Dot4 fluid during assembly but packed under the dust seal  with this PBR brake lubricant.

The pistons were a little tight to push back into the bores as I couldn't find my small c-clamp but a pair of old pads and a wooden wire brush handle pushed them back into their respective bores evenly.



Here is the finished left brake. The refirbished right caliper looks the same now as well.



The wiring harness with it's crumbly black outer coating was cleaned - wrapped in black insulating tape and then encased in a spiral plastic casing which I found at the autoshop - nice and slim and fits into the original plastic clips.

Bill.

[s class]

That looks like a satisfying day's spannering.  Thanks for sharing. 

[johnnyw116]

looks great ! a week or so ago i did the same thing for a friend of mine on his 1969 250C i only did the front calipers also by the way          

greetings : johnny  .      

[13B]

Bill, did you split the callipers or just change the piston seals?  I notice the Haynes manual says no need to split the callipers and the place who rebuilds mine for me splits them based on which seals come in the calliper rebuild kits... if there are no channel seals in with the kit then he doesn't split the callipers...

I sent the W116 fronts callipers (Ate, like yours) to be rebuilt and they didn't change the channel seals, but later I sent some callipers from a W108 280SE 3.5 and the kits for those included channel seals so he split those to replace the channel seals as well.

I.

[koan]

The wiring harness with it's crumbly black outer coating was cleaned - wrapped in black insulating tape and then encased in a spiral plastic casing which I found at the autoshop - nice and slim and fits into the original plastic clips.

That's a good fix for the aging harness, I have some of that small spiral wrap somewhere, I'll be doing the same.

koan

[WGB]

Bill, did you split the callipers or just change the piston seals?  I notice the Haynes manual says no need to split the callipers and the place who rebuilds mine for me splits them based on which seals come in the calliper rebuild kits... if there are no channel seals in with the kit then he doesn't split the callipers...

I sent the W116 fronts callipers (Ate, like yours) to be rebuilt and they didn't change the channel seals, but later I sent some callipers from a W108 280SE 3.5 and the kits for those included channel seals so he split those to replace the channel seals as well.

I.

Unless you want to complicate things or have a strange leak I would not split the calipers. My kit did not include these seals and there was no reason that I could see that required the calipers to be split to enable the workings to be overhauled satisfactorily.

looks great ! a week or so ago i did the same thing for a friend of mine on his 1969 250C i only did the front calipers also by the way           

greetings : johnny  .       

Hi Johnny,

I have kits for the rears and will probably get at least one of them done today if I get enough time.

Bill

[TJ 450]

Nice work, Bill.

Those wear sensor harnesses can look rather unsightly with the crumbling insulation... that's a good fix. I used the split tubing (not the convoluted stuff) and it looks a bit average, plus it doesn't fit the clip at all.

Tim

[nathan]

thankyou for continually reminding me of my poor financial decisions! ha ha, i think those cars have provided peices for just about every 116.org forum member in wa!

[WGB]

thankyou for continually reminding me of my poor financial decisions! ha ha, i think those cars have provided peices for just about every 116.org forum member in wa!

I think it is mentioned as a continual vote of thanks tio Nathan and not concerning the wisdom of your fionancil managment but it is suprising what useful bits and pieces come off something that at first glance appears to have little worth.

As a counterpoint - I managed to turn the flats off the right rear brake pipe from the T-piece at the rear to the right flexible hose, even using a flare spanner - the one on the wreck had been cut to remove the callipers.

It does not look easy to replace as it goes over the rear diff subframe and is available ex Singapore for $125 plus GST - should be arriving after the weekend.

Bill

[TJ 450]

I haven't replaced the rear brake hoses on my 6.9 for that reason. I started rounding off the flats... It's nice to know that the line isn't too expensive. Presumably it would need to be bent to shape though.

Tim

[WGB]

A flare spanner on an 11mm fitting is even more necessary than on a bigger fitting.

I'd better not talk too soon as I still have to loosen the other end of that same pipe and it has awkward access - but apart from that one joint all others have opened without damage.

Bill

[koan]

I've mentioned this before but a good tip I was given years ago after making a mess on some brake plumbing is to give the fitting a few decent taps with a hammer.

A tee piece for instance, try and hold something solid against one side and hit the directly opposite flat a few times.

Brass and steel fittings only, don't hit cast parts - like the suspension regulator assembly.

Works on all flare connections, A/C hoses, dry sump hoses, suspension pipes, the lot.

I've managed to avoid rounding anything on the M-B using this tip. I know access is difficult sometimes but it the fitting feels like it's about to round off some extra disassembly is worthwhile to get better access.

koan

[s class]

Agreed koan, that works well.  Another trick I've been using, is that in cases where you suspect you will have problems, such as these brake lines, try first giving it a fair amount of force in the tightening direction, before attempting to loosen.  In many cases, even stubborn joints will turn slightly in the tightening direction much easier than in the loosening direction.  Obviously don't go overboard.  Even if the fitting doesn't turn in the tightening direction, this process helps to 'gather up' material on the flats such that there is actually better purchase on the fitting in the loosening direction.  This trick works briliantly. 

[TJ 450]

Another thing to consider is the profile of the flare nuts... there's hardly any surface area, plus most flare nut spanners are machined in such a way that there are rounded edges. This makes the situation even worse as far as purchase is concerned.

I'll have to try those methods as well, Koan and s class... this sort of information is priceless. Of course, I have already rendered the rounded-off nuts and thus the brake lines useless if removed.

Tim

[kastad]

Do anyone of you guys know the parts number for the wire harness and/or connectors to the brake pad wear sensors? Easy to find sensors, hard to find the wiring and connectors...