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MG MGA - Caliper dust seal question

Hi Folks. I started rebuilding my brake caliper today. I installed the fluid seal in the cylinder groove, and installed the piston. The rubber dust seal and metal retainer are causing a problem though. THe metal retainer does not want to seat properly in it's bore. It goes in on one side and pops back out on the other. I tried using a brass punch and hammer, tapping gently arounf the circumference of the metal retainer, but it simply does not want to go in evenly. I tried lubricating the edge of the metal retainer with red brake grease, hoping this would help ease the retainer into the bore, but it did not help. Does anyone have any idea as to what I am doing wrong, and how I can get the dust seal with metal retainer to seat in it's bore? I rebuilt my calipers back in 1980, and dont remember having this much difficulty fitting the dust seals and meal retainer back then! Thanks! Glenn
Glenn

A piece of wood large enough to cover the whole thing can be used to push it together at once. Be carefull, tap lightly until it is started all around once started you can drive it home. If struck too hard to soon you can bend the ring.
Good luck
R J Brown

Hi RJ. Unfortunately, that wont work. The piston has to go in before the dust seal. The piston protrudes from the bore, and the dust seal sits below the surface of the piston. It is therefore impossible to get a chunk of wood across the dust seal, because of the protruding piston. A large diameter piece of pipe the right size could perhaps be used, but I dont have a suitably sized pipe. I somehow managed (with extreme difficulty) to get the 2 dust boot retainers into each side of one caliper, but they simply refuse to go into the second caliper!
Ah, British engineering at it's best! lol, Glenn
Glenn

First--check the edges of the metal dust seal. They're stamped and some have a bit of a "flange" along the edge. Carefully file this away, in fact, you could even file a bit of taper to them to help ease them into the bore. Then I took a piece of masonite, and cut a hole the diameter of the piston. glued another piece over it. worked pretty well to apply even pressure all the way around the seal to seat it. It has to go in perfectly straight....You can't work it in around the edge--it'll just bend.
R. L Carleen

Glenn:

I don't understand the comment about the piston having to "go in before the dust seal." I just finished rebuilding a set of MGB calipers and there was no problem with setting the dust seals and retainer rings (which are exactly the same as the MGA) before I pushed in the pistons. (It has been many years since I rebuilt my MGA calipers and the only thing different is the center locating pin on the MGA units.) However, if the metal retaining ring is bent when it is set, it can squish the dust seal out a bit, making the piston harder to insert (I know from experience), but if the retaining ring is set properly, the piston will easily go in if it is pre-lubed with brake fluid.

In any event, there are three things that come to mind that might help you. One is to buy a new interseal between the caliper halves and split the unit for better access. Another is to find a piece of PVC pipe that has an i.d. that is close to the o.d. of the piston. Cut a piece that is slightly longer than the protruding piston then cut a split in the side so that you can open it up or compress it to fit most of the seal circumference. Using this adapter, it should be possible to put a piece of flat metal across the diameter and push the retaining ring home with a C-clamp.

The third suggestion is to remove the piston and use the flat piece of wood recommended in the previous post or a flat piece of metal to seal the seal without the piston in place. However, I would use a C-clamp rather than tapping it home since bridging the seal exerts a more uniform pressure across the diameter.

Steve
Steve Brandt

Glenn,
In a caliper rebuild article in MGA! a while back, Dave Ash suggested (as did Mr Carleen) grinding a slight taper on the edge of the retainer. I used this method after destroying two dust seal retainers. To quote our British friends, "it worked a treat!" I used a bench grinder. Also a flat piece of steel and modifed C-clamp to press into place.
Good luck,
Gerry
G T Foster

Hi Folks. I took the advice to grind a bit of a taper around the circumference of the metal dust seal retainer. I also finally found a suitably sized piece of pipe. With these changes in tactics, the retainers popped into place without any further difficulty! Guess you could say that I now have a pair of trained seals!!!! Thanks for the assistance everyone! Cheers! Glenn
Glenn

Glenn. With that pair of trained seals why not send them to the ice floes off Newfoundland and curtail the killing of the little white beauties.
Sandy Sanders
Sandy Sanders

This thread was discussed between 27/02/2006 and 03/03/2006

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