Disassembling MGF rear caliper
Got round to doing this - had two spare calipers I did a test run on. Both seized handbrake mechanisms!
One was a standard, straight from factory, 10 year old caliper. The other was a fairly new reconditioned caliper I bought for 90 quid including exchange for old one.
Unscrewed the main piston from the caliper, looking down into the chamber:
Circlip #1
Use a pair of quality, long nosed circlip extractors, and take it out. It's a bit fiddly, but takes less than a minute.
Once released, the clip should come flying out. It is holding a 'cage' and spring inside, which sits on a washer.
Water has got in here, but these can be cleaned using a toothbrush and abrasive sponge (like ones you do the dishes with). It comes straight off. I had the sink with hot water and washing up liquid.
Underneath, yes another circlip. Do the same as above, and remove the clip. Underneath is a shim which holds the main piston screw. Once released, the screw should come straight out (removing the shim). If it doesn't, use a pair of pliers on the handbrake mechanism bolt at the bottom, while pulling (not damaging the thread) on the main screw.
Once it comes out, you are presented with this:
This is in order of reassembly:
The whole lot at the bottom is totally corroded, and the space it occupies needs to be cleaned of all the gunk.
I used carb cleaner and hot, soapy water with a tooth brush. Standard calipers have a needle bearing in the handbrake chamber, whereas refurbed ones are replaced by a simple plastic sleeve. A couple of the needle bearings had disintigrated, a couple had fell out. These can be placed back in the cage.
The handbrake mech rotates and turns a shaft, which has an assymetrical hole:
This presses against a small, separate 'nub' (shown here in all it's corroded glory):
Which pushes the main piston screw up slightly (it sits in a hollow at the bottom).
While cleaning the components up, I sprayed the cleaned caliper casing with a coat of zinc primer spray, and then silver enamel spray paint.
I then reassembled, and coated the whole lot in a layer of grease to prevent rust.
The main piston can be disassembled by removing the circlip inside. The internals are 'sprung', and corrosion can also hinder this mechanism.
One was a standard, straight from factory, 10 year old caliper. The other was a fairly new reconditioned caliper I bought for 90 quid including exchange for old one.
Unscrewed the main piston from the caliper, looking down into the chamber:
Circlip #1
Use a pair of quality, long nosed circlip extractors, and take it out. It's a bit fiddly, but takes less than a minute.
Once released, the clip should come flying out. It is holding a 'cage' and spring inside, which sits on a washer.
Water has got in here, but these can be cleaned using a toothbrush and abrasive sponge (like ones you do the dishes with). It comes straight off. I had the sink with hot water and washing up liquid.
Underneath, yes another circlip. Do the same as above, and remove the clip. Underneath is a shim which holds the main piston screw. Once released, the screw should come straight out (removing the shim). If it doesn't, use a pair of pliers on the handbrake mechanism bolt at the bottom, while pulling (not damaging the thread) on the main screw.
Once it comes out, you are presented with this:
This is in order of reassembly:
The whole lot at the bottom is totally corroded, and the space it occupies needs to be cleaned of all the gunk.
I used carb cleaner and hot, soapy water with a tooth brush. Standard calipers have a needle bearing in the handbrake chamber, whereas refurbed ones are replaced by a simple plastic sleeve. A couple of the needle bearings had disintigrated, a couple had fell out. These can be placed back in the cage.
The handbrake mech rotates and turns a shaft, which has an assymetrical hole:
This presses against a small, separate 'nub' (shown here in all it's corroded glory):
Which pushes the main piston screw up slightly (it sits in a hollow at the bottom).
While cleaning the components up, I sprayed the cleaned caliper casing with a coat of zinc primer spray, and then silver enamel spray paint.
I then reassembled, and coated the whole lot in a layer of grease to prevent rust.
The main piston can be disassembled by removing the circlip inside. The internals are 'sprung', and corrosion can also hinder this mechanism.
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