Singer Owner November/December 2003

Roadster Repairs Master cylinder overhaul 4AB, 4AC, 4AD Roadster

Ashley Crossland

It started one Saturday earlier this year when we were due to take the 4AC Roadster to a rally the following day. Backing the car out of the garage revealed the fact that there was no brakes. A quick check round to make sure there was fluid in the reservoir made me reach the conclusion that the master cylinder had "gone". So I didn't take the car to get it filled up with petrol, neither did I wash and polish it, but carefully returned it to the garage. We went to the rally the next day in a different car! I don't think that there is anything suspicious about the brake master cylinder having gone. Again it's down to the rubber seals having been in the cylinder for over 20 years. However, I should have expected a problem since I have previously mentioned in the Singer Owner about rubber components failing. Naturally current materials are an improvement so we don't necessarily see the same problems with our current cars. Also with hindsight I had changed some seals in the front wheel cylinders and it's easy to see that bleeding the brakes would have pushed the master cylinder onto crud that it's never touched before. The new wheel cylinder rubber seals were done for the MOT, but afterwards the master cylinder was then living on borrowed time.

Now before I describe the overhaul of a Roadster master cylinder can I say that the general advice on such brake components is to fit a complete unit and not to fit a seal kit. This is a far safer proposition, but I do accept that for our Roadsters there is little likelihood of getting a new master cylinder and if it's old stock the rubbers in it might be 50 years old.

Getting at the Roadster master cylinder is quite easy. The car doesn't need jacking up and access is quite simple from above.

First of all, tie a bit of string between the drivers door handle and a side lamp so that the door is held open at a convenient angle. If the seat is over the driver's side front floorboards, slide it back, but there is no reason to remove the seat. Roll back the carpet and undo the screws holding down the front drivers side floorboard and then remove same. The master cylinder is now visible.

Slacken the pipe ends and let the hydraulic fluid drip into a suitable container placed underneath. Slacken off the nuts - note do not disturb the union bolts.

Three long bolts secure the master cylinder to the side of the chassis. Remove these three bolts, taking hold of the master cylinder as it becomes loose. Fold back the rubber concertina dust cover to expose the spring clip that holds the pushrod

Into the end of the master cylinder. Remove the circlip with some thin-nosed pliers, not circlip pliers. If the seals have little grip, the spring in the master cylinder may push out the piston. Take hold of the master cylinder and take your bench.

To fit new seals in the master cylinder, follow the instructions in the kit. However, one important point to take note of is the removal of the large end nut. This is screwed onto the body of the master cylinder and makes a pressure tight seal on its flanged face with a copper washer. It is very important not to distort this flanged face of the nut and therefore to remove the nut you should use the correct fitting socket or ring spanner. I would not advise using an open-ended spanner, nor stillsons, nor clamping it in the jaws of a vice. Anyway 11/16" BSW is the size.

In an old kit, Girling kindly provided a list of cars. Although our beloved Singer Roadster may only exist in limited numbers, there are some more massed produced cars using this kit and therefore it has a chance of being available, one would hope, for some time to come.

The master cylinder kit is Girling SP1211/1 and OK, there are probably fewer Allards and AC 2 litres about than Singer Roadsters, but Austin A40, A70, A90, Ford Consul and Zephyr MK1, Jaguar VII and VIII with Rover 60 & 75's should keep us going!

However, back to re-assembly of our master cylinder. One of my pet subjects is the subject of copper washers and how they start off as soft copper, but get work hardened after being tightened up in a joint. Thus they are not as effective in sealing if they have been used before. New kits come complete with new copper washers and you must always use a new copper washer for the big end nut. Obviously do not use new washers in "trail assemblies".

The rest is straightforward, although one tricky bit is the joining back of the master cylinder to the push-rod. Make sure that the circlip is correctly in place and properly seated in its groove. Pull and tug on the pushrod to make sure it won't come out. When you are satisfied line up the master cylinder with the holes on the chassis and assemble the side plate with two bolts through the master cylinder and one bolt through the spacer tube. Incidentally, this spacer tube is important!

The rest of the re-assembly is straightforward. Screw up the hydraulic pipes, fill with hydraulic brake fluid and bleed the front brakes. Check the entire system for fluid leaks and test the brakes. If you have any doubts or problems, then get it sorted professionally.

The moral of the story? Well I suppose it has to be that rubber compounds have improved, but we are faced with the fact that 20 years ago, rubbers were only good for a 20 years life. If you are keeping rubber parts "in stock" for the future, there are recommendations that you should follow, like keeping them cool; dry, free from grease and out of the light etc., undistorted. The recommendations can be found by reference to them, not here.