autojumbled

Refurbishing mkII MR2 Brake Calipers

Ben Tyrie

Rather worryingly I didn’t notice the binding front brake on my MR2 until very recently after driving through a large puddle after a long drive.  The plumes of steam from the front passenger wing indicated a very hot brake disc!

A 30 minute reccy revealed a very gummed up piston and a generally sticky mechanism that was not allowing the piston to travel all the way back into the caliper – time for a clean up job and whilst I’m at it I might as well  have a go at refurbishing all 4 corners seeing as the rear drivers side gets a little stuck after being left a couple of days, as well as clean and paint the calipers.

Parts list:
Front Brake Caliper Seal Kit (Genuine Toyota) – Part number:  04479-17020
Rear Brake Caliper Seal Kit (Genuine Toyota) – Part number:  04479-17040
500ml of DOT4
Copper grease
Hammerite Smoothrite
Paint brush
Penetrating spray (WD40/PlusGas)
Bleed nipples (front) – part number: 47547B (47547-20010)
Bleed Nipples (rear)  – part number: 47547C (47547-22020)

Tools:
Jack
Axle stands (enough to get the car up at all corners)
Calliper rewind tool
Socket/bar suitable for wheel nuts
Ratchet
17mm socket
14mm socket
14mm open spanner
8mm spanner for bleed nipple

Obviously the most important parts required for the refurb are the seal kits.  I opted for the genuine Toyota kits as they contain everything required to completely replace all perishables on the calipers.  One kit contains enough bits to do 2 calipers. i.e one axle.  The seal kits were bought from www.tcbparts.co.uk as they were in stock and were able to get them out to me next day.

http://www.brakes4u.co.uk/ for braided brake lines.  None on the shelf but they had HEL make some up and ship them out next day.

Front caliper rebuild kit Rear brake rebuild kit

The actual rebuilding of the calipers was a time consuming process.  Making sure all the new seals and components are correctly fitted took some time.  The basic process of removing the parts can simply be reversed when fitting the new parts.  I referred to a very comprehensive guide from MR2OC written by ‘MonkeyMax’ for the mk1 braking system whenever I was unsure of the next step or to double check bits.

(I have also saved MonkeyMax’s brake refurb guide on this site in case it goes missing from the MR2OC site…again)

Rather than rewriting a brand new ‘how to’ guide, I’m just going to point out the bits I had particular problems with or any tips I picked up along the way.

To completely break down the calipers, the pistons had to be removed and cleaned.  For the rears this means winding out the piston using a piston winding tool (funnily enough) – this took a lot of effort!  I found slowly working the piston back and forward helped to loosen it before having a big go at fully unscrewing it.  Also, using a straight bar with a socket head attachment (from a ratchet/socket set) helped get a much better grip on the winding tool.

The front pistons were a pain to remove too.  I ended up wedging the caliper between my foot and a block of wood (against a wall).  Then using a strong long flat bladed screwdriver under the lip of the piston, worked it free by hitting it with a heavy mallet. Needed a vice really.

Worth noting that once the pistons were cleaned and free of rust and dirt, they glided nicely in and out of the calipers – massive improvement!

Front caliper before cleaning Front caliper after cleaning Cleaned pistons and painted calipers Seals and retaining rings fitted

One thing Max’s guide didn’t include was details on the locations of he brake pad anti-squeal retaining clips.  As I forgot to take photos of the calipers before dismantling them I was forced to find some pictures on-line.
Thankfully, www.mr2turbo.info came good and I found a couple of good angles of close up caliper shots with which to use as a reference. (see below)

Front caliper anti-squeal clips Front caliper anti-squeal clips Rear caliper anti-squeal clips

With everything bolted back on including the new braided hoses, it was time to bleed the system.  Unfortunately this didn’t quite go to plan!  Using the 2 person method (1 pumping the brake pedal and holding it whilst the other opens and closes the caliper bleed screws) we bled the system fully from the rears to front multiple times but were still finding that the brake pedal had no resistance and felt extremely ‘floppy’.  We went around again a few times but with not a lot of luck.

As there was a tiny bit of braking available (only when the pedal was fully pressed to the floor), I drove the car to JDModified (previously 3S Services – an MR2 specialist) for James and the guys to have a look over it.  It’s worth mentioning now that I had tried multiple methods of bleeding throughout the week including a pressure operated system, as well as replacing the bleed screws.

The guys bled the system and found no air.  They then bled the master cylinder by pumping the brake pedal, holding it, and then cracking off the nuts on each pipe on the cylinder (after covering it with a rag to catch any escaping fluid) – this seemed to firm up the pedal a little!  After this, they adjusted the pedal within the car (something I hadn’t actually considered) and the braking was all back to normal!

A picture of the final product – they need another coat of paint really before they are finished I think but all in all, very nice.  Will get to try them out properly soon as I have track time booked at JapFest (held at Castle Combe).Refurbished Caliper

To re-iterate, make sure to check out MonkeyMax’s guide before starting work and it’s probably worth having it to hand during the refurb too.
Also, thanks need to go to Peter Gidden of SBits for offering his assistance on bleeding methods and other advice.