I’m not a motor mechanic but having read bits on the internet and stuff on this Forum I thought I should be up to changing the rear brake pads on my 2001 Mk 2.5. I started with the o/s and everything went well until I tried to fit the caliper over the new pads. Of course it wouldn’t fit because I had only wound the piston back enough to clear the old worn pads, not the new ones. I then tried to wind the piston back further but it wouldn’t move. I did manage to wind the piston out a bit to see if it moved at all but of course I couldn’t then get the old pads back on either. It was suggested I try the n/s to see if that went okay. Unfortunately on that side I can’t even wind the piston back enough to swing the caliper out of the way. I have had advice from Robbie and Rob and having tried all their suggestions they are both a bit flummoxed. It is possible the handbrake isn’t fully releasing despite being fully backed off, the outer adjuster may have worn enough to become ineffective, or something inside the caliper may have broken.
My question is, before I start throwing money at this, are they any members knowledgeable on this topic who are close to Bromsgrove in Worcestershire and are prepared to come and take a look to make sure I haven’t missed anything or am doing something stupid. I appreciate that this is poor timing given the current situation but I’m sure we could do this in a safe way and I can provide nitrile gloves if needed.
the handbrake is mechanical so if it is not releasing will stop the caliper piston retracting sufficiently. As the pistons on both sides are affected I would suggest that if the handbrake is the problem, it is the first single cable to the lever that is too tight. I know that you have removed the handbrake covers and unwound but perhaps need unwinding a few more turns and pushing down.
any proud corrosion on the piston under the gaiter will stop the pistons winding back past the main caliper seal. Wind the piston forward so the gaiter starts to extend. It can then be taken off the piston and pushed down the piston to reveal the state of the surface that has to get past the seal. Typically water can condense under this gaiter and cause rust. No real issue with pad wear and retracted position moving forward. Pitting will not cause issue but any proud rust will make it very hard, if not impossible to use the adjuster to get the piston in to the bore beyond that seal.If there is rust, wind piston forward, clean it all off flush with a stanley knife blade. Clear all rust debris out of gaiter and lubricate with silicone grease or red rubber grease, if that is what you have.
EBC Ultimax are a common pad for this application, so I think it very unlikely that these have been supplied with too thick a lining and not fit for purpose with newish discs. Most people fitting these would likely be fitting brand new disks anyway. Rear calipers are the same for all standard cars, MK1 to MK2.5, exception being SVT sport big brake calipers that have a larger piston.
The handbrake adjuster is completely removed. The threaded rod is poking up by about 1/2" and if you push it down it springs back up.
We extended the o/s piston as far as we dared by Jayne gently pushing the brake pedal. As far as we can see there is no sign of corrosion or rust under the rubber. Obviously we can’t get to the n/s piston.
I did remove both outer adjusters to check them as you suggested. Both seem fine with no obvious wear or rounding off. The Allen key fits well with no suggestion of it turning within the head.
I had the same issue where I changed the front disks and pads and then had an issue with the rears. Apparently it is to do with the handbrake not releasing properly to enable the calipers to go back into the calipers. If you google it, there are a couple of youtube videos, which are worth looking at…I have sent mine to the garage as they are doing some other stuff anyway. I bought all the bits and it is not too expensive to get a proper mechanic to do it…
An update. I have now removed the handbrake cable from both calipers so that can no longer be considered a factor. Unfortunately it has made no difference to either side so I have to conclude that something in the calipers is broken.
I did make some progress shifting the n/s caliper. I used emery paper to remove the rust from the edge of a small section of the disk to see if that was enough to swing the caliper past. It still wouldn’t budge so I hit it with a hammer and eventually it came free. I then had a real struggle to get the inside pad off and when I did the back of it was rusty in parts, as was the front of the piston. No shims with these pads, or with the new EBC ones.
Next step is to get the calipers off. Since the calipers are coming off I will now get the discs swapped (or skimmed) at the same time. Progress of sorts.
Hi, I’m new here. Just reading the posts, I didn’t know the handbrake would play a part regarding the caliper piston to be seized? Seeing as you have a MX5 Mk2.5, which I have myself. There is adjustment gear cap on the inside face of the caliper. Remove that cap and use Allen key and rotate fully anti clockwise to retract the piston into the caliper.
Keep us posted, very intrigued to how your problem gets rectified.
If I understand it right, if the handbrake is partially applied then it can prevent the piston from retracting fully back into the caliper, hence the need to back off the handbrake adjuster first.
I spoke to my local garage last night and they said they could clamp off the hydraulic lines, remove the calipers, refit the wheels and drive the car to the garage. They came round this morning and did try turning the piston back with the Allen key whilst using a clamp to compress the piston but it wouldn’t budge, so it was off to the garage for new calipers and discs, as well as the new brake pads.