Rear Brake Caliper Won't Retract

zephyrus17 · Postby **zephyrus17** » Sun Mar 27, 2011 3:55 pm

I've encountered a problem where my rear brake caliper won't retract no matter how much I spin the allen key. This happened after I got a friend to pump the brakes because I wanted to see how much the caliper travelled. I have already 'opened' the caliper with the allen key. He pumped and the caliper wouldn't retract and it just came out more and more. It just seemed like the fluid wouldn't return to the cylinder. Then I (on hindsight) stupidly forced the caliper back with my thumbs. He pumped it a few times again and it seemed to retract. So I started to turn the allen key to open it again and it just wouldn't move. Spinning the allen key to 'close' the caliper (extruding it out of the body) was ok.

I looked around and some on the forums said the auto adjuster was misaligned, so I tookout the caliper from the bore and used fingers to tighten down the adjuster and then put the caliper back in. That still didn't work. It seemed that if I twisted, say, 20 turns to extrude the caliper and then screwed the adjuster in, I could only screw the allen key 4 turns before I couldn't turn anymore.

Any advice on what to do?

zossy1 · Postby **zossy1** » Mon Mar 28, 2011 9:24 pm

zephyrus17 wrote:I've encountered a problem where my rear brake caliper won't retract no matter how much I spin the allen key. This happened after I got a friend to pump the brakes because I wanted to see how much the caliper travelled. I have already 'opened' the caliper with the allen key. He pumped and the caliper wouldn't retract and it just came out more and more. It just seemed like the fluid wouldn't return to the cylinder. Then I (on hindsight) stupidly forced the caliper back with my thumbs. He pumped it a few times again and it seemed to retract. So I started to turn the allen key to open it again and it just wouldn't move. Spinning the allen key to 'close' the caliper (extruding it out of the body) was ok.

I looked around and some on the forums said the auto adjuster was misaligned, so I tookout the caliper from the bore and used fingers to tighten down the adjuster and then put the caliper back in. That still didn't work. It seemed that if I twisted, say, 20 turns to extrude the caliper and then screwed the adjuster in, I could only screw the allen key 4 turns before I couldn't turn anymore.

Any advice on what to do?

I'm not exactly sure what you are saying. Are you telling us that you removed the caliper from the rotor and then pressed the brake pedal? You "wanted to see how much the caliper travelled"? Are you talking about the piston?

If you did this, with respect, that was a very poor piece of judgement.

I am assuming the piston is still in the caliper though...

You then say "He pumped and the caliper wouldn't retract and it just came out more and more."

I hate to sound harsh, but it seems you do not understand how hydraulics operate. I strongly suggest you entrust this job to someone who knows what they are doing.

zephyrus17 · Postby **zephyrus17** » Mon Mar 28, 2011 9:42 pm

I do know how hydraulics operate, but I thought (wrongly, of course) that when the pedal was lifted it would 'suck' the fluid back into cylinder. The caliper piston did come out and I've managed to get it back in and working again. It was just very tough getting the auto adjuster back into the piston. I sure have learnt my lesson.

zossy1 · Postby **zossy1** » Tue Mar 29, 2011 9:24 am

You were lucky - you should have your brakes bled, and watch fluid levels carefully for a couple of weeks to make sure you didn't damage anything back there.

zephyrus17 · Postby **zephyrus17** » Tue Mar 29, 2011 10:37 am

Indeed I was. Next time I should think 4 million times before I do something out of plan. My problem was exactly similar to this guy: http://www.mx5oc.co.uk/forum/forums/p/15176/90276.aspx

zephyrus17 · Postby **zephyrus17** » Wed Mar 30, 2011 3:07 pm

Update. With the help of a simple G-clamp I managed to put the auto adjuster back into the piston. The side with the circular wire faces out and the the side with the crescent-shaped plate faces in. Then it's just a matter of putting it back in, spinning it a few times to get the adjuster to 'catch' onto the screw thread, and then just using the allen key adjustor as per normal to retract it. I bleed the brakes as well with this 'One Man Bleeding Kit' tons of bubbles came out. Brakes now feel better than ever.

That said, the ultimate lesson is to not do stupid things! :oops:

Thanks for all your help guys