New rear caliper binding brakes

[Dr Who]

I have just changed a rear nearside caliper on my T270 2011 (after failed an MOT due to caliper seized, and had eaten most of the brake pads (disk was OK i.e. legal).

(Long story, deer ran out in front, did cosmetic damage beyond value of car, so insurance co. wrote it off CAT N, and suspended the insurance.  I bought it back, tidied up the damaged front plastic, but can't get insurance reinstated until car has new MOT. They will allow me to drive to MOT station. So, it failed the MOT, nothing to do with the front cosmetic repairs, because of a cut in an almost new tyre, and a NSR brake caliper probably seized, with one burnt out pad.)

So, bought a new pattern caliper online (eBay), looked good, fitted well, kept the old disk, and fitted new pads from Halfords (Bosch).  Put the wheel on, brakes seemed to test ok,  BUT couldn't go for a test drive (apart from a slow 30 yards up a private road) as the car isn't insured.

Took for re-test this morning, failed on brakes binding and hot, at the new caliper. Have spent the afternoon stripping down again, caliper was tight onto disk even without 'service brake' (electric handbrake) operated, had to prize it out. Checked the original fitting was OK, the 'wind back' pad on the end of the piston/cylinder was in the correct position to engage the stud on the brake pad, and the electric handbrake cable wasn't tight when not operated. (Did I miss something?) So re-wound the cylinder enough to get the caliper back on, aligned brake cylinder head with pad stud, and bolted on. 

At that stage the wheel hub (including brake disk) would rotate freely. 'Service brake' was off, so started engine and my helper tried foot brake, which operated OK, while I checked the brake, hub locked. Released footbrake, checked hub, still rotates freely.

Operated the 'service brake', checked hub, not fully locked (assume too much slack in caliper/shoes/disk for one operation of the 'self adjusting' cylinder). Released 'service brake' from driver seat, and re-operated. Now hub/disk are locked. Released 'service brake', hub and disk VERY stiff to rotate (had to use long screwdriver in wheel studs (wheel not on of course). Operated the foot brake, then released, and if anything hub stiffer still to rotate.

So, the question. Have I done something wrong? or...

a) does this look like the self adjust mechanism for the 'service brake' is not releasing fully (the cable goes sloppy though)?

b) Also, as the footbrake does seem to cause even worse binding (once it has started) is this all likely down to the 'self adjust' mechanism not 'backing off' in the new caliper?  Or something else?

Any thoughts would be gratefully appreciated. Thanks, Paul.

 

 

 

 

 

 

 

 

[Jim-p]

Just to preface, I'm not an expert. After you change and bleed the new caliper. I'd try to test the two applications of the caliper separately, the hydraulic (regular foot brake) and the mechanical (handbrake). While still jacked up: For regular foot brake; start the car press the brake till it stiffens and then release. Can you now turn the wheel, it probably won't be free free but you should be able to turn it without too much difficulty. Now press the brake again till it stiffens and then apply the handbrake and release the handbrake again, now can you turn the wheel? If there is major resistance after either then I'd be looking at the caliper, worth checking the guide pins as well to ensure they move smoothly.

Replaced both my rear calipers a few weeks ago and i couldn't actually press out the piston on one side with my foot to bleed it, had the to start the car to move the piaton. Never seen that happen before. Has been working away fine since and passed the NCT.

 

[Jim-p]

2 minutes ago, Jim-p said:

Just to preface, I'm not an expert. After you change and bleed the new caliper. I'd try to test the two applications of the caliper separately, the hydraulic (regular foot brake) and the mechanical (handbrake). While still jacked up: For regular foot brake; start the car press the brake till it stiffens and then release. Can you now turn the wheel, it probably won't be free free but you should be able to turn it without too much difficulty. Now press the brake again till it stiffens and then apply the handbrake and release the handbrake again, now can you turn the wheel? If there is major resistance after either then I'd be looking at the caliper, worth checking the guide pins as well to ensure they move smoothly.

Replaced both my rear calipers a few weeks ago and i couldn't actually press out the piston on one side with my foot to bleed it, had the to start the car to move the piaton. Never seen that happen before. Has been working away fine since and passed the NCT.

 

Apologies, I reread your post and I think what I posted won't be of much help. Except for pump the foot brake till it stiffens before applying the parking brake after pads change. Also, you have service mode which I don't have or don't use.

[Fenix262]

Could be the sliders and pads need some copper grease putting on to assist with movement

[avetoy]

On 7/9/2024 at 8:56 PM, Dr Who said:

does this look like the self adjust mechanism for the 'service brake' is not releasing fully (the cable goes sloppy though)?

 

I think that is the case if the wire is loose. Try to turn the lever back by hand or with pliers. If it helps, then there is something wrong with the  caliper, i.e. the lever is somehow stuck. First aid could be WD40 and a new (stronger) spring...

[Dr Who]

Thank you Jim-p, it was very useful to get your feedback that the wheel hub (wheel off) when turned manually wasn't 'free running' and there was some brake friction (new pads) even when working 'normally', as that had worried me. You also had a good point to check which of the two mechanisms (mechanical hand brake, or hydraulic footbrake) caused the brakes to bind, which i had also tried to separate. It seemed like from each wind-back trial, handbrake was probably OK, but footbrake started the binding. After that, the handbrake would turn a stiff-to-rotate-by-hand hub  into a virtually locked hub (even when handbrake was returned to 'off'). To me that all pointed to the self-adjust mechanism in the replacement (new) caliper not backing off. I tried discussing this with the eBay supplier by eBay messages, but they seemed to be looking for a way to say I had done something wrong, and either way were going to 'discuss' for a length of time that I hadn't got, So, rather than get another one from the same online supplier, I got another new one from a different online supplier who offered 2-day delivery, as I needed this urgently for a free re-test 'within 10 days'. Note the past tense, needed, because I believe this is now SOLVED. It was the self-adjust mechanism, faulty in the first new caliper.

The second new caliper arrived yesterday, and was fitted within ten minutes (you get to be expert after having one on/off about ten times, to keep winding-back the cylinder from 'locked', for more tests). The second new caliper worked perfectly right from the get-go. and is chalk-and-cheese to the first replacement caliper. I have been for a ten mile test drive, and although the disc gets very warm, I can still touch it comfortably, and more the point it is the same/similar temp to the other rear disc. The two front discs are both much hotter, but still touchable. (I haven't gone round feeling discs temperature after a 10m run before, so have no yardstick, but this seems likely about right?).

An aside: The first online supplier, emailing from China, asked me for details of the braking system, and the car, being diameter of disc, thickness of disc, make and model of vehicle, year of vehicle, and engine. Whilst I know this is a potential trap, I also know I bought the correct unit, so did supply these details, as a requirement before they would refund. They emailed back this morning to say that the caliper was only suitable for 11mm discs, not the 9.8mm disc I had (I had measured the disc with a digital caliper).They offered a half-price refund. So, I think their returns department are non-technical and may not understand that the 11mm thickness NEW disc has a wear tolerance down to 9mm, after which it must be replaced, and that my 9.8mm thickness disc is well within tolerance, and was passed as such by the MoT examiner on 4/7/24. I have replied to that effect, asking for a full refund, (response awaited). This faulty caliper has cost me a lot of time and stress, and I have had to buy a second litre of DOT-4 brake fluid for all the bleeding(!), and am still awaiting (due today) a flexible brake hose I ordered for the nearside rear, just in case there was an internal collapse causing resistance in fluid returning, hence caliper sticking (had to order hose just in case, as have MoT re-test on Monday 10am, last day. It wasn't the hose in the end, but I will change it anyway 'sometime', having bought it.... )

Thank you again for the input Jim-p, it did help, and the support made me feel less isolated.

Best wishes, Paul.

 

 

[Dr Who]

Thanks for the input Fenix262. I had considered the sliders, and pads, and had lubricated them with a 'suitable' grease. Won't get into what, as there are more views on 'suitable' online than there are greases available. Whichever one you choose, someone else says 'DON'T USE THAT !', because it either dries out and turns to dust, or won't take the heat, or eats/perishes the rubber gaiters, etc, etc.  In passing, I think the old pad backing plates were part of the original problem, albeit the caliper piston was badly corroded and wouldn't return. The old pad backing plates were slightly longer and a slightly different end angle (compared to the new Bosch pads I fitted). I hadn't initially realised, because I needed to prize the caliper and pads out with two large screwdrivers, as it was all seized. Thought no more until I had a problem with the new caliper/pads, then thought to try the old pads again, just to see if the same problem (binding) showed. Anyway, the old pads backing plates didn't fit well, too long and slightly wrong shape (were on the car when I bought it). These would have jammed against the disc when operated, and destroyed the friction material and worn the disc. I made sure the new pads slid easily, and also the two caliper slider pins.

Please see the (also rather long!) reply I have made to Jim-p above, as in the end the fault was the self-adjust mechanism on the new caliper, remedied only by buying a second new caliper (and still arguing about a refund with the first supplier).

Thank you for your input, I hadn't initially greased the pad backing plates in their springs, thinking clean may stay working longer than any grease, but they do slide better having lubricated (for now), and that is what I need at this moment!

Thanks again, Paul.

 

[Dr Who]

Thank you avetoy. 

The mechanical brake assembly did seem to be suspect initially, as even when the cable was slack, the brake didn't release. There are two limit studs for the operating of the lever, and it was going between these studs, the first when operating (nearly to stud) and the second when releasing (all the way back to stud by spring pressure).

The second problem of the hydraulic brake also causing a 'binding' and not releasing made me look at several possibles: sticking new pad back-plates (wedging against the disc), brake fluid not back-flowing after brake pedal released perhaps due to a collapsed liner inside the flexible brake hose, or a fault in the self-adjust mechanism on the new caliper. I eliminated the first two options, by greasing the pad plates so they slid very easily, and loosening the hydraulic cable connection onto the caliper when the brakes had failed to release (which still did not cause the brakes to release). That really only left one more suspect, and the fault was the self-adjust mechanism in the new caliper.  I had to buy a second new caliper to prove this, but that's a whole other story, please see the lengthy reply I have made to Jim-p above.

Thank you again for your input, the feeling of support alone is so valuable when I was starting to feel very despondent...  

Best wishes, Paul

[Dr Who]

Final comment: Got the MOT PASS this morning, no binding, so the brake binding issue was definitely the first NEW caliper faulty. Company in China originally offered me 50% of purchase price as a refund (and I get to keep the faulty caliper. Huh?). Have now upped that to 80% refund and I still keep the faulty caliper, scrap metal. I must say the thought of not having to deal with, and argue with, them again is seductive, but so is getting all my money back. Considering it... but either way they will get a stinking eBay review.

[Paul john]

1 minute ago, Dr Who said:

Final comment: Got the MOT PASS this morning, no binding, so the brake binding issue was definitely the first NEW caliper faulty. Company in China originally offered me 50% of purchase price as a refund (and I get to keep the faulty caliper. Huh?). Have now upped that to 80% refund and I still keep the faulty caliper, scrap metal. I must say the thought of not having to deal with, and argue with, them again is seductive, but so is getting all my money back. Considering it... but either way they will get a stinking eBay review.

That refund offer is standard practice for Chinese companies these days. Be prepared for a very long wait if you expect 100% refund. Possibly 2 weeks of email silence, in my experience.

But… well done on MOT pass

[TonyHSD]

eBay returns and complains best to be dealt directly through the eBay app or customer service. Full refund guaranteed and no need to deal with dodgy traders. 

[Dr Who]

...which was the purpose of the exercise, just such a shame it became so extended and stressful due one new faulty item, that mimicked the original fault, Paul.