Leaking from the rear calipers was an all too common problem prior to 2016, when Caterham stopped using remanufactured Ford Sierra calipers and started using reproduction units. So I wasn’t expecting this problem.
I always knew I would need another brake bleed, because the initial brake fluid bleed was done without the handbrake cable connected to the rear calipers. I have aways found that a good wiggle of the handbrake releases the last few air bubbles trapped in the rear calipers, which makes the brake pedal nice and firm.
Just as I finished the bleed on the left-hand side rear caliper, I noticed my right-hand side caliper had a puddle on the floor.
Ordenrially this would be no problem, Caterham even said they would send a replacement caliper, but they were out of stock with no expected time of arrival. This happened at the start of the COVID-19 lockdown in the UK.
I decided to order a seal kit from Bigg Red , and take the caliper apart myself.
Removing the piston using my piston wind-back tool was simple enough. I found a number of online copies of Ford Sierra workshop manuals that covered the procedure of strip-down and rebuild. I only wanted to replace the piston seals, not the handbrake seals, because there was no evidence of leaks from that part of the caliper.
I discovered some deep scratches in the piston, which could easily be felt with my finger nail. Therefore Bigg Red to the rescue again with a replacement piston. Interestingly, the new main piston seal was much tighter on the piston that the original seal, which would slip down the piston on its own accord. For this reason, I decided to replace the piston and seals on the other caliper as precaution.
Refitting the piston was simple enough with plenty of the supplied assembly grease, but there is a trick to get the dust seal on the piston and in the caliper. I found the best way to fit the dust seal is to fit it to the piston first, then pull it down so the seal extends beyond the piston; this extended seal can them be inserted into the caliper. With the dust seal in place, the piston can be wound into the caliper.
The the calipers refitted, brakes bled, handbrake cable fitted and brakes bled again, I finally have the brake pedal feel I was hoping for.