HALF SEALS

1

With our MG on the ramp, the first job technician Ian Redfern did was to raise the back of the car up on jacking beams to enable the rear wheel to be removed. The brake drum is secured by two set screws and rather than destroy the heads if they are seized, use an impact screwdriver to loosen them. Winding the brake adjuster back allowed the drum to be removed.

2

Even with the nearside brake adjuster wound fully out, it still required a fair bit of gentle persuasion to remove the brake drum. Never lever a tight drum off the hub, as you’ll only end up distorting the back plate. Centre the brake shoes by hitting round the circumference of the drum with a hide or copper-faced mallet – don’t use a hammer as this could shatter the casting.

3

Despite cleaning out the rear brakes while the car was being serviced last month, oil from the differential had found its way past the worn hub seal over the last 100 miles or so. Even though the brake shoes were contaminated with oil, our MG’s braking system had miraculously passed the MoT when tested in the traditional way using a Tapley meter.

4

Not a pretty sight. Note how centrifugal force had caused the oil to spread out from the centre of the brake drum. The numbers around the casting provides information about the drum’s maximum size as well as the minimum thickness of the friction material. When machining a scored drum, make sure the dimensions aren’t exceeded.

5

After removing the split pin, Ian used a ratchet gun to slacken off the big nut securing the hub carrier to the half shaft. A top tip here is to put the car in gear to stop the shaft turning while undoing the nut, which can be very tight. With the nut undone, the hub carrier was pulled off its splines. There’s no need to use a puller, as it should come off by hand.

6

Next job was to remove the oil-stained brake shoes and set them to one side with all the return springs and handbrake linkage still attached. Take a couple of photographs before removing these items as its can be confusing which holes the springs fit back into. Brake shoes are sometimes sold on an exchange basis but ours would end up in the scrap bin.

7

The back plate on our MGB is secured to the axle casing by four 9/16-inch bolts. These had been done up far too tight and technician Ian had to use quite a lot of force to undo each one. Before the plate could be removed and cleaned up in the parts washer, the brake line leading to the rear wheel cylinder was disconnecte and sealed off.

8

A clever idea to stop brake fluid leaking out of the hydraulic system if you haven’t got a suitable plug whenever a line or hose is disconnected from a brake cylinder or caliper is to use a short length of old brake line with the end flattened over and attach it to the disconnected pipe. Ian’s got two of these in his toolbox – one with a male and another with a female union.

9

Once the back plate was removed, the carrier containing the duff oil seal was released from the end of the axle tube. Before doing this, it’s a good idea to remove the cone shaped spacer the inner surface of the seal runs on, as this will allow the carrier to move sideways by tapping it gently with a hammer rather than using a screwdriver to lever it off the end of the axle.

10

With the oil seal carrier soaking in the parts washer, the next step was to wash all the road dirt and old oil from the end of the half shaft and clean the machined face of the axle with a stiff brush and a slosh of brake cleaner. It didn’t matter if any foreign material got into the bearing at this stage as the half shaft was going to come out so a new one could be fitted.

11

As the outer race of the bearing is only an interference fit inside the axle tube, the hub was refitted so a slide hammer could be bolted to the wheel studs and used to extract the half shaft from the axle casing. This job could be done using a three-legged puller but care is needed so as not to damage the threads or spines on the end the half shaft.

12

A high capacity hydraulic press is definitely required to remove the old bearing and press the new one in place on to the end of the half shaft. The press needs to be a free standing one with an adjustable table with enough height to allow the long half shaft to stand on its end.

13

Before pressing the new bearing onto the end of the half shaft, don’t forget to replace the spacer that locates against the collar at the end of the shaft’s machined surface. There’s no need to fill these bearings with grease as they are lubricated with oil from the differential.

14

After relocating the half shaft into the axle tube, the outer race of the wheel bearing needs to be fully seated in the machined recess. Here Ian uses a stout brass drift to seat the bearing by gently tapping around the circumference until it’s fully home. The change in note the drift makes when hit will denote when the bearing is fully located in its seating.

15

With the seal carrier firmly held in a vice, Ian used a blunt punch to remove the worn oil seal. This should come out easily after being struck a couple of times on opposite sides but while doing this be careful not to damage the surface the seal sits on.

16

Although Ian used a special tool to fit the new seal, you could use a large socket to drift it in place but be careful not to damage the delicate inner surface of the seal while doing this. To make this stage a little easier, smear a small dab of oil around the recess before pressing the seal home.

17

As the oil seal kit didn’t include a new paper gasket, Ian applied a very light smear of high-temperature silicone cement around the machined surface of the cleaned-up casting before relocating it on the end of the axle. Don’t use too much of this stuff as it will squeeze out when the bolts are tightened and could end up getting into the bearings.

18

Before refitting the oil seal carrier, don’t forget to replace the conical spacer to the end of the half shaft. The inner surface of the seal runs on this spacer and before replacing it, carefully inspect the surface after its been cleaned up for any pitting or roughness, as this could damage the new seal and you’ll have to do the job again.

19

Before bolting the back plate on to the axle, the brake line was reconnected to the wheel cylinder. Ian had previously removed the rubber boots and blown out any debris with an airline. A top tip is to run the bolts through the seal carrier before offering up the back plate to ensure everything lines up.

20

Although the old nearside brake shoes on our MGB were covered in oil, the car didn’t pull to one side or feel odd in anyway when braking hard. Before taking the springs off and disconnecting the handbrake linkage, it’s advisable to take a photograph of where everything goes to make reassembly easier. Failing that, do one side at a time!

21

After refitting the bottom return spring and handbrake linkage to the new shoes, Ian carefully positioned the ends of each shoe into the slots in the wheel cylinder. Once the shoes were in position, Ian replaced the top return spring and used a pair of long-nosed pliers to fit the spring-loaded steady pins that help keep each shoe inline with the backplate.

22

After a good soak in the parts washer the friction surface of the brake drum was deglazed with a small length of emery cloth. This will help the new shoes to bed in quickly. Top tip to help fitting the top return spring before the drum goes back on is to use a pair of adjustable grips to seat the shoes but don’t grip the friction material as this is easily damaged.

23

Applying a smear copper based grease to the set screws securing the drum to the hub should stop them seizing. Last job was to bleed the rear brakes, not forgetting to top up the master cylinder before opening the bleed nipple on the rear wheel cylinder. Fitting the temporary plug only required the brake pedal to be pushed a couple of times to bleed the system.

24

After checking everything was tight and there were no leaks from the hydraulic lines, Ian refitted the road wheel and torqued up the nuts to the required setting. With one side complete, it was now time for a well- earned cuppa and slice of Tony’s wife Pauline’s world famous almond and cherry cake before moving on to the offside and repeating what we’ve just done.