First forum post - help with rear brake

[patb]

Hi, father in law gave us his Jazz so learning about these. Put new pads on rear nearsise today, they fitted fine and wheel moved freely when fitted whilst jacked up but after applying brake, the pressure does not release fully so the pads are still rubbing. I have put loads of grease on the two sliding pins but no difference. Is it the piston not returning freely? When I dismantle everything and then out back together, it feels free again. Grateful for any advice, hate paying for the garage to do it. Hurt pride, hurt wallet.

[culzean]

What kind of grease did you put on slide pins ? Cannot use petroleum based grease, needs to be proper brake grease, petroleum based greased will swell the rubber seals ( there are seals in the slide pins ) and cause the rubber bellows to fail. Also if you put too much grease on slide pins and it gets into the blind holes they slide into it can cause hydraulic lock and stop the pins pushing into the holes, which stops the calipers moving properly. It only needs a smear of the correct grease on the pins.

There are also some protrusions on the back of pads that need to line up with slots in ends of pistons, if these don't the pads will end up not being parallel to disc surface.  Did you use a proper piston retraction tool to push pistons back and rotate them at same time ?

How tight were the ears of the pads in the carrier's, if they are not a good slide fit they can bind and stop caliper equalizing, Did you use high temperature brake grease on the ears, you often need to remove the stainless steel shim that clips into grooves and properly clean behind it, if not the pad ears may not slide freely.

Plenty of threads on here about proper way to change pads etc.

If you are not sure what you are doing get car into a garage to get it sorted.

[patb]

Thanks for the quick reply, re the correct grease, I will chek this but no way there was time for any chemical reaction to stop things working, thanks for the other tips, I will review them all, I had not idea of all these variables,

before I apply the brakes, I can see the caliper moving with little gap on either side if I push it in and out, after applying the brake, the pads are locked against the disc and the caliper with all movement gone so I dont think its the pads sticking, there is no room for them to move if that makes sense,

Iused a large scredriver to trun the piston back and made sa not of the orientation before rotation to tryu and keep the alighnment, it seems impossible to visuially check once the caliper is bolted back on


have Tues off so will have another go, grateful for an further comments,
 

[Darryl]

Hi, father in law gave us his Jazz so learning about these. Put new pads on rear nearside today, they fitted fine and wheel moved freely when fitted whilst jacked up but after applying brake, the pressure does not release fully so the pads are still rubbing. I have put loads of grease on the two sliding pins but no difference. Is it the piston not returning freely? When I dismantle everything and then out back together, it feels free again. Grateful for any advice, hate paying for the garage to do it. Hurt pride, hurt wallet.

And the offside  pads?


Surely you haven't just put new pads in one side have you

[patb]

Ill do the otherside next but if I cant teach myself how to do one side correctly, little point in doing the other side, garage is 300 meters away so have that as an option, car not usable untill I free up the binding brakes but it can limp to the garage.

[patb]

Quick question, if I want to check to see if the piston is returning back or is jamming, (therefore keeping pressure on the pads), is it OK to use the brake very gently/partially with the caliper off off so I can visually see the end of the piston?

[SuperCNJ]

Sounds to me like it could be a seized caliper. If that is the case then it'll need replacing.

[culzean]

Quick question, if I want to check to see if the piston is returning back or is jamming, (therefore keeping pressure on the pads), is it OK to use the brake very gently/partially with the caliper off off so I can visually see the end of the piston?

You will most likely blow the piston out and be in all sorts of trouble - if you do not have the skills take the car to a garage and then sign up for car maintenance lessons... Brakes are too important to mess with.

[patb]

Thanks for all the advice, being stubborn and not needing the car urgently, (with the sun out), I'm happy to keep trying. The caliper was working fine before I put new pads on. Would the new, wider pads lead to a seized caliper?

Also, on a wider not, Im trying to get my head around whats going on inside the piston. When it's wound back in, the is no exact tolerance, just as long as there is enough space to locate the new pads. So Im curious re how the piston adjusts iteslf to the new pads and also how it adjusts over time to pad wear. It somehow winds itself out ? so there is some kind of thread mechanism? New fluid enters into the system as the pistons push further out?Always curious to know these things,

5/6 just to update, I did the otherside and it everything worked fine, I noiticed that the piston was much easier to turn back so guessing the it's sticking on the problem side.

Yes, had a really good look and found a cut in the seal that fits around the piston. New seals ordered