Freeing wheel cylinder locking plate

[RDKeysor]

I am in the process of trying to replace the rear brake cylinders on my '60 BN7. The Haynes manual describes a simple process for removing the locking plate on the backplate of the rear drum brakes simply enough: "With a screw driver prise the locking plate (part 2) and spring (part 4) apart and carefully tap the lock plate from beneath the neck of the wheel cylinder." Haynes is kind enough to illustrate the parts and a rubber seal absent on my cylinder. Well, I've been "prising" for a couple of hours, even cutting a hook in a bit of hacksaw blade and trying to work part 4 from beneath part 2. I haven't budged the small plate (4) under the larger plate (2). I'm about to give up and pull the innards from the old cylinder and replace them with the innards from the replacement, but perhaps some one knows a simple way of doing what I started out to do, replace the cylinder. I will add that I have successfully removed the handbrake lever (part 3, not the brake lever in the cockpit) in the failed (desperate would be more truthful) hope that it would help me free the locking plates. I've squirted in WD40, pried, prised, tapped and cursed without success. Help!

 

[Patrick67BJ8]

I am in the process of trying to replace the rear brake cylinders on my '60 BN7. The Haynes manual describes a simple process for removing the locking plate on the backplate of the rear drum brakes simply enough: "With a screw driver prise the locking plate (part 2) and spring (part 4) apart and carefully tap the lock plate from beneath the neck of the wheel cylinder." Haynes is kind enough to illustrate the parts and a rubber seal absent on my cylinder. Well, I've been "prising" for a couple of hours, even cutting a hook in a bit of hacksaw blade and trying to work part 4 from beneath part 2. I haven't budged the small plate (4) under the larger plate (2). I'm about to give up and pull the innards from the old cylinder and replace them with the innards from the replacement, but perhaps some one knows a simple way of doing what I started out to do, replace the cylinder. I will add that I have successfully removed the handbrake lever (part 3, not the brake lever in the cockpit) in the failed (desperate would be more truthful) hope that it would help me free the locking plates. I've squirted in WD40, pried, prised, tapped and cursed without success. Help!

Those locking clips are hard to undo but easier to reinstall. You have to get a spacer under the edges of the prongs and then with a third tool tap on it until it slides apart.

 

[steveg]

Tap the outer (springier) one out this way; the inner one from the opposite direction.

 

[RDKeysor]

Definitely tried tapping the outer plate, ditto the inner. I briefly tried a suggestion from the search function at this site similar to what Patrick suggests above, which is to slide something between the two locking plates and then tapping off the outer one as shown in Steve's photo. My understanding is that the lower plate has a locking point that engages the larger top plate. Wedging something between the two plates is supposed to unlock that feature. I will give it another try tomorrow. I'll report back. Thanks all!

 

[steveg]

The locking device is the turned-up edges visible on the right side of the lower locking plate.

 

[RDKeysor]

Well, Eureka after several hours. Steve's photos were diagnostic in getting the locking plates free. My problem was that none of the margins of the inside locking plate were visible as they can be seen in Steve's photos. The first shows the tabs already free, the second shows them in the locked position. Unfortunately, my locking plates are much different than those in Steve's photos. The cuts where the tabs can be seen engaging the top plate go around three sides of the tabs. I had no visible margin to get a pry tool under the top plate to disengage the tabs. When I inserted a tool under the tab end, it went under both plates, and thus didn't disengage them. Only the tips of the tabs were visible. Ultimately, I trickled some of my acetone/power steering fluid rust breaker down between the plates. I then pressed an awl tip down on the top of one tab--this is all I could see of the lower plate--pushed it down, and then drove the small-diameter awl between the plates. The top plate then pushed off just as my responders said. I provide all of this elaboration for those who look this up later. Again, had my plates been identical to the one's Steve supplied, I doubt that I would have had the difficulty I encountered. The info provided by the forum members was critical in solving my problem. I had employed virtually every tool I owned, magnifiers, mirrors, hammers, you name it. This was tougher than installing a new 3.5 differential on the previous weekend, though I had plenty of help from our Healey club members.

 

[steveg]

RD - does your setup look like these parts? I don't have the little u-shaped parts at the lower left and wonder how they fit.
Was looking at Moss photos - this is their Fitting Kit, PN 582-225:

 

[RDKeysor]

My car had only the four pieces at right that are similar to the parts in your photos. There were no rubber parts like those pictured and the two bits below them. As you might guess, I was able to remove the second brake cylinder in a couple of minutes, again using a scriber-like tool to push down one of the tabs, and then continuing to push the tool between the two locking pieces. I was unable to see the seam between the two pieces, as the one on top was larger than the lower one. I took some pictures to illustrate this but haven't been able to download them. I was installing two new Moss-sourced wheel cylinders after discovering a very tiny amount of fluid leaking from one while installing my new differential a week ago. At this point I have rebuilt the front calipers after a leak, installed a new 7/8" master cylinder to go with the new British-Victoria sourced servo (Series 1 cars didn't have these), and the braided lines front and rear. Hope the heck the rear cylinders finished the job. I'll try to show a picture of the locking pieces from my car tomorrow.