I recently replaced the rear calipers on the MGF, which solved the handbrake problem. Incidentally it also improved the overall efficiency of the braking system.
Being an inquisitive type, I decided to strip the old callipers down, to try to discover the problem with the handbrake mechanism.
Let me say right away:- For me, this was an exercise of curiosity only.
I do not know how long this method will keep the handbrake working properly.
Don't mess with your brakes unless you know what you are doing.
Having said all that, this is what I did.
The caliper showing the handbrake mechanism.
PART A. STRIPPING, FREEING AND REBUILDING.
1/. Firstly, I disengaged the spring using a pair of long-nosed pliers. The spring can now be removed and at this point,
attempt to rotate the mechanism. The lever
should move freely against the pressure of an internal spring.
Ha! The mechanism was actually stiff, almost to the point of seizure!
[imghttp://www.the-t-bar.com/photos/david/stuff/_DSC0003a.jpg[/img]
Nb. Please note that any movement of the lever will move the caliper piston out from the cylinder. Using the long-nosed pliers, screw the piston back in (clockwise).
(in this picture the piston boot has been removed)
2/. Remove the 17mm nut and spring washer, and you will see that the lever has a rectangular locating hole that fits onto the shaft.
This is merely a push-fit, honestly! Some Plusgas and a small persuader enabled me to loosen and remove the lever.
3/. Now you can see the shaft seal, beneath which
should be some high temperature grease to lubricate the shaft, allowing easy rotation.
This grease degrades over time and usage, and causes the seizing problems. By carefully easing the centre of the seal aside, I was able to insert the feed tube of a can of Plusgas, and used it to flush the solid remnants of the old grease out.
4/. Now I temporarily refitted the lever, and repeatedly manipulated it until the mechanism became free.
Again, you need to remember to screw the piston back in as you rotate the lever back and forth.
5/. The lever should now rotate easily.
The internal spring should return the lever from this position(a)
to this position(b).
6/. I then refilled under the seal with Red grease, which is a special grease for brakes, and rotated the lever to spread the grease further into the problem joint.
7/. I then rebuilt the mechanism by reversing the steps 1 and 2.
I REPEAT:-Don't mess with your brakes unless you know what you are doing. However, if you want to refit the caliper and use it, it's up to you. If so, follow part B.
Part B - REFITTING AND HANDBRAKE ADJUSTMENT
1/. Remove the sliding mechanism(in the concertina sleeves) on the carrier. Clean and re-grease with high temperature grease. Refit to carrier.
2/. To refit the caliper to the car, first refit the carrier to the hub(2x17mm bolts). This enables you to refit the brake pads onto the disc.
3/. Trial fit the caliper unit over the disc and pads, if necessary screw the piston in(clockwise) or out(anti-clockwise) until the caliper is a close fit(1-2mm clearance total.)
4/. You can then re-bolt the caliper to the carrier(2x12mm bolts), and re-connect the brake pipe. Now re-bolt the handbrake arm to the caliper(2x12mm bolts).
5/. Repeat 1-4 for the other caliper.
6/. Make sure that the handbrake cables are free and adjust them (under the centre console) until you can attach both back to the calliper handbrake levers. WITHOUT MOVING THE HANDBRAKE LEVERS. In other words,
pull the cable to the lever, do not pull the lever to the cable.
7/. Adjust the cables again until the handbrake levers just begin to move. Your handbrake is now adjusted.
8/. Bleed the brake system. Test the brakes and handbrake are operating properly before road testing.