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Hot Rear Disc

Cruiser84

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Joined
Nov 30, 2022
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Hi folks, I had a right side rear disc that was getting hot from not releasing fully. So I replace the disc, caliper, pads, and guide pins rubber sleeves. The brake ran cool for about a month but now gets hot trips over 20km. Wheel bearing seems ok and parking brake shoes are not rubbing.
Any ideas why the brake is still sticking?
Thanks in advance.
 
Last edited:
Thanks for your reply. I have backed off the hand brake on that side. The centre of the disc where the hand brake shoes contact doesn't get hot, only where the pads contact the disc face and not all the time??
I have replaced brake fluid and bleed the system with ignition on to activate the ABS pump. I think this is the correct way to bleed the brakes.
The replacement caliper wasn't OME .
 
I'm wondering if there is an imbalance in original old caliper one side and the new non original on the offending side, but I guess as the problem was there before, that blows that theory out of the water. I always replace items in pairs anyway, so starting with a known level playing field.

As Karl says check h/brake pads for even/uneven wear.

Also if you have a spring weight balance thingy - the type you weigh your holiday luggage with, or your catch with when fishing, with handbrake and both rear wheels off (chocks and stands) and both side studs in near same exact position, choose the same stud each side, hook the spring balance weight on and pull until the hubs just start to turn.
Note the weight pulling each side to see if there is more drag on one side than the other for the disc brakes, then with the handbrake partially engaged, repeat process for that.
It may give clues ?
 
Without crawling underneath as i recall all the calipers on 120's are of the opposed piston design so no worries about slide pins sticking.
All i can think of is the pads are too tight a fit in the caliper and so failing to retract properly, i'd be inclined to whip them off give the sides of the pad back plates a good rub down on the concrete to remove any excess paint so they are a looser fit, then give a wipe of coppaslip onto those edges to help keep them lubed in use.

Presumably the holes where the locating pins slide through the pad back plates allow movement of the pads in use, they can benefit from a wipe of lube too, but where contact with rubber comes ionto play i prefer to use the correct red brake grease which won't perish rubber parts, if no contact with rubber coppaslip is fine.

Park brake as you know has nothing at all to do with the service brakes, and unless the cable is seizing or the shoes are deliminating or overadjusted there really isn't much to go wrong, in my humble its the best park brake design ever fitted and glad all of our cars have that fine and expensive to make design.
 
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Without crawling underneath as i recall all the calipers on 120's are of the opposed piston design so no worries about slide pins sticking.
Ummm, I think the rears are sliders? ... But I havent had to do the brakes on mine yet, so you might well be right!
 
Questioning myself now Karl and happy to be wrong, if they are sliders then they need lubing and making sure there's nothing catching preventing them releasing fully when one releases the brake.

The Forester brakes are sliders all round, but could have sworn the 120 rears were opposed design.
 
Found a pic!
 

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No not at all, I had to check as well ! Plus the front are opposed pistons arent they?

As you say then, slider pins number one suspect?
 
I don't know he 120 and i don't want to know about traction control but assuming it uses the brakes to keep you in a straight line might swapping wheels alter or move the problem ?
 
Yes fronts are 4 piston opposed jobbies...speaking of which, Cruiser84 whilst you're working on the brakes its worth servicing the front brakes well, the inner lower piston is very prone to seizing up, luckily being opposed piston if you whip one pad out at a time you can lever one piston in and the mate it shares its cell with should slide out just as easily, easiest pistons to exercise in their bores you can have.
 
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