Technical Rear brake caliper sticking

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Technical Rear brake caliper sticking

only a thin layer of grease is needed on slide pins.
Make sure to clean out all the wrong grease.
To me it sounds like you are doing all the correct things.
 
Are the pads tight fit in the calliper bracket or a loose sliding fit?
 
I'll update when have some new info, I am pretty sick atm (some kind of flu or something).
When I tried to put pads back to cleared brackets it was hard to fit them. But when they were fitted the move was nice...
Another idea I got is to grind the pads "noses" which fits to those brackets (some paint streaks could be on the bottom sides).
 
Very sorry to hear you are ill and wish you fast recovery.

Yes to filing or grinding the noses of pad metal plate . that was what I suggested but your description of noses is perfect.
You only need to grind one nose on each pad. Grind enough off so they are easy fit and move very freely.
Don't worry if you have to grind a little metal off as well as paint.

Get well soon, from England
 
Thanks for reply.
I have bought new guide pins, some grease is attached to packaging so I am planning to change those completely.
Yup, rubber boots are fine, both of them are not damaged with "Bosch" logo on them, so they are genuine ones.
Those mouting brackets were cleaned with brake cleaner and lubed with grease, but they were coated with black paint (brake pads fitted are also genuine ones). I suppose that this could be also an issue, so I have prepared set of new ones (Textar, without paint) and I am going to change them. However on the right side they are coated too (I think that, because I was not disassembling that side) and it is not sticking.

Do you have any tip for a suitable grease? I got silicone one from ATE (bremszylinder paste, blue packaking aka "toothpaste", part no. 03.9902-0501.2./02 - cant post links), but I use it only when assembling calipers - lubraction of piston and piston seals, it could be used with DOT 3 and DOT 4 brake fluids. I did some searching and suitable is Bosch Superfit paste, but it is similar in composition as Plastilube...so?

Another thing I have noticed is that rubber sleeved pin is on the top position in the caliper carrier. When I looked up for those in Eper I have found that those pins with rubber should be located in the bottom position - could this be an issue?
Silicone grease is best. It won't damage rubber.
 
So, update incoming...

I have disassembled the right side and check the upper guide pins and yes, it had rubber sleeve on it so my guess of badly fitted pins was not right. I put it all back and moved to right side.
Removed the wheel, loosen the bolts holding caliper to guide pins, removed pads, brackets and caliper bracket with guide pins. Some brake dust was sitting in the places, where pads brackets are sitting so I cleaned with steel brush without any problem.
Then I moved to guide pins. I removed both, the grease in the bottom one was pretty dirty, even the pin had a little rust marks on it.

So I decided to put on a new guide pins, especially when the upper one has slighlty damaged that rubber sleeve. Everything was fine, the grease included in packaging of guide pins was clear silicone one, so same as ATE to fiting the brake pistons. (y)
I lubed the rubber sleeve, fitted it on the guide pins without any problem, same with both rubber boots. Then cleaned the guide pin slots at caliper bracket with brake cleaner (nearly hit my eyes with that and old grease :D). Both pins move freely, without any problem.

Then I moved to brake pads, I used 180 (or 200) sandpaper to remove paint on those "noses" I mentioned before.

I put brand new pad brackets on the caliper bracket, and lubed pads with a little bit of copper grease. The fitting was fine and pads are moving nicely and freely. The fitted caliper and brake pads are here.


I have also created video of the spinning wheel and caliper moving... [ame]https://youtu.be/iok1TBOGgJY[/ame]
First part is the movement of the caliper. As you can see, the caliper/guide pins is/are moving freely without any problem. Second part is same state, only with fitted wheel, as you can see, it can spin nicely. Third part, after I pressed the brake pedal maybe twenty times (with started engine) to pull the pistons out in order to adjust handbrake mechanism, you can see it is noticable braking :cry: In the fourth part of video, after I pushed the handbrake leveler at caliper, it spins more freely but it is not ideal.
All in all, everything I have done so far seems to be not working :bang: The wheel heats up (there is approx 25-32°C), the right one wheel has about 40°C, the left wheel has about 60-66°C, same as brake rotors, the left one has 80-90°C (even more than front, both of them had about 70°C), the right one 60°C.

So the last step, I will do is to clean, and refurbish the old caliper (I already have rubbers, new piston etc.) and fit it back with hopes it will help. If it do not help, then the last thing I did not check is the brake hose.
 
Hi ,
Each time calliper bracket is removed and put back on it is in a slightly different location. Due to size of mounting bolt holes.

Re Check wheel drag after 300kms to allow pads to match disc.

Watched your video and I agree it looks like there is slightly too much drag.

Good luck.
 
Yup, I am aware of that. However even when I was changing brake components on different cars, such drag I have seen only when there was problem with guide pins or something else.

I am rebuilding the old caliper now, I am about to fit back the piston with threaded mechanism and I will try the function with pressure air. The handbrake mechanism is working perfectly without any stuck, the rust which creates between handbrake operational arm and caliper was cleared (and it was pretty siezed, nearly impossible to remove internal mechanism). I will fit back the original one as I think that the problem is either in caliper (piston seal or threaded mechanism) or hoses. I'll update when got some new info.
 
I hope that this will be last update :)

I bought eazybleed system and used garden pressure sprayer (with pressure gauge) as an source of pressured air. So the change of calipers was question of minutes.
The rebuild caliper mechanism is working fine, seals are tight. Handbrake mechanism is pulling piston out and it stays pulled. The wheel rotates freely, little drag is visible, maybe little bigger than on the right side, but nothing as terrible as it was.
I have not tried it on road yet, but I suppose, that it will be fine. Will post some info.
 
I hope that this will be last update :)

I bought eazybleed system and used garden pressure sprayer (with pressure gauge) as an source of pressured air. So the change of calipers was question of minutes.
The rebuild caliper mechanism is working fine, seals are tight. Handbrake mechanism is pulling piston out and it stays pulled. The wheel rotates freely, little drag is visible, maybe little bigger than on the right side, but nothing as terrible as it was.
I have not tried it on road yet, but I suppose, that it will be fine. Will post some info.
Very pleased things appear to be working for you at last.
A good lesson for all of us that new parts can be faulty.
Will you be able to return the faulty new caliper?
 
I bought it on eBay, I am able to return it, but I will remove the piston out and fix. I'll keep it, who knows how long will me rebuild last :)

Yesterday I have done approx 50 miles, the wheel is not hot at all, the temp seems to be similar as on the right side. So I get some experience at least :-D
 
I think you did a great job rebuilding your original caliper and it will last a very long time.
If it was my choice I would send caliper back for refund , not have to store it just in case it is needed. Also the piston retraction will only work if the groove the piston seal sits in is correctly shaped. If the caliper is incorrectly made rebuilding it won't help.
Clearly it is your decision to keep or return.
Thank you very much for update on your success. We should all learn from your experience,[emoji3] .
I think there are more faulty new parts now than 10 years ago.
Jack
 
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