Brake System Maintenance


Routine maintenance of the braking system is primarily about adjustment because there is no automatic take-up of wear in the brake shoes. The 1,000 mile service schedule includes checking the free travel at the brake pedal, which is bizarre because in Section M, the workshop manual comments: “the correct amount of free movement between the master cylinder push-rod and piston is set during erection of the vehicle and should never need alteration.” In reality, checking the free pedal movement is only needed if the components have been dismantled and settings disturbed. Checking the fluid level in the master cylinder is, however, called for at the same interval and this makes much more sense. No one wants to discover he has a fluid leak by hitting the pedal in an emergency stop and getting zero response. For the same reason, the 1,000 mile service schedule also calls for visually inspecting brake lines for leaks or damage. When topping up, also check that the air-hole in the reservoir lid is clear.

Actual adjustment of the brake shoes is recommended every 3,000 miles, although the rate of wear will depend on how the car is driven. Section M also recommends adjustment if, during use,  the pedal travels to within 1” of the floor. Most experienced drivers can feel when the brakes are losing their “edge”.

Both front and rear brakes are adjusted in the same way, though at the front there are two adjusters per wheel whereas at the rear there is only one. This is because the front brakes take the lion’s share of the braking effort and are equipped with twin leading shoes. This means that both shoes have an actuating cylinder and pivot positioned in such a way that their braking force is enhanced by the rotation of the brake drum.

Although the brake drums and the wheels have corresponding holes so that the brakes can be adjusted without removing the wheels, this is false economy of effort. I generally adopt the discipline of removing the wheels and the brake drums before adjustment. This allows me to clean out the drums (wear a face mask to do this because brake dust does nasty things to your lungs). It also gives me early warning of any fluid weeps from the wheel cylinders and lets me check for the amount of wear in the shoes. Uneven wear in the front shoes will indicate that one of the cylinders may be seizing up. This is a problem that arises when cars are laid up for long periods.

The brake adjusters are ratcheted cams (a.k.a. “snails”) and these can wear over the years. Turning them against the force of the shoe springs should require a significant twisting effort and if they spin round too easily this suggests that their serrations are wearing too much. The risk is that they can fail all of a sudden, spin back to zero adjustment and you find that you suddenly have massive pedal travel. This is less serious than a full brake failure but can feel equally scary.

While the wheels are off, it is also a good idea to look at the condition of the flexible hoses. They won’t last forever and as soon as the rubber looks dry and cracked it is best to put new ones on. If you have a few extra quid looking for a good home, you can get the Goodridge-type braided hoses that are tougher, last longer and give a firmer feel at the pedal.

So, assuming all is well inside the drums, you fit the drums back on and rotate them to the position where the adjusting screws are visible through the adjusting holes. (A small flashlight is handy for this). Using a sturdy screwdriver, you twist the cams up to the point where the drum is locked solid. Then back off one click. This should allow the drum to rotate freely again. On the front drums, you spin the drum through 180? and repeat the exercise.

If you are adjusting the brakes after fitting new shoes, put the drums back on but get into the car and operate the brakes hard a few times. This will ensure that the shoes are properly centred in the drum. Only then do you adjust them as above.

Separate adjustment of the handbrake should not be necessary because it uses the same shoes at the rear but actuates them mechanically rather than hydraulically. Sometimes, wear in the actuating lever pivots and wearing surfaces will cause too much free  movement, so check for this and replace the parts if necessary. However, if you are sure your rear brakes are in good order but there is still too much handbrake lever travel, adjustment is available by tightening a nut on the rear compensating link, where the two side cables come together.


If you believe your brake pedal travel is excessive even after adjusting the brakes up, it may be that your drums have excessive wear. This can generally be confirmed by looking for a ridge between the wearing internal surface in the drum and its outer edge. Don’t be tempted by solutions that involve skimming the drum and shimming the adjusters. The only real answer is to obtain new drums. As they are the same as those fitted to the MGA 1500, this is not as difficult as you might imagine. New drums are not cheap but as far as I am concerned, the brakes are one area where economy is the least of considerations and safety is worth every penny invested.

Worn shoes can be replaced with new. Again, commonality of parts with the far more numerous MGA makes this easy and relatively cheap. You may have to exchange your old shoes. When the car was manufactured, brake linings were usually riveted to the shoe but now it is far more common for them to be bonded, which has the advantage that more lining is available for the braking process. Stick to good quality known brands (see above comment about investing in staying alive).

If you find a leaking wheel cylinder, then, here again, replacement is the best bet.


Any dismantling of the brake hydraulics means that the system will need to be bled. This is the rather gruesome term for the process whereby all air is expelled from the hydraulic lines. This is important because air will compress under pressure whereas fluid will not. Any air in the system will cause a vague or spongy feel at the pedal. The workshop manual describes the traditional bleeding method but I swear by the “one-man” kits like the Eezibleed, especially the type that uses air pressure from a tyre to push the fluid through the system. Take care: a lot of fluid moves under pressure and if the reservoir runs out you will push air into the system and you’ll have to start all over again. However hard I try, I always manage to spill fluid so I put down a dust-sheet or newspapers.


Apart from being topped up at service intervals, the master cylinder needs no interim maintenance but eventually it will start to leak, generally because the internal rubbers begin to perish and wear. More frequent top-ups are a clue to a more significant loss of fluid. A disadvantage of the way the Magnette is assembled is that the push-rod side of the master cylinder is obscured from view. This means that leakage from the bores is not casually observed. One has to go looking for it. This involves grovelling in the driver’s footwell and looking up to where the push-rods pass through the bulkhead. In extreme cases you may see drips on the carpet first. A probe with the fingers will also detect any fluid emerging from round the push-rods.

Removal of the master-cylinder is relatively easy. Use a syringe or something similar to remove as much fluid as possible from the reservoir. Take care because it is corrosive on paint-work. Once the brake lines have been detached, the dual-cylinder body is held by only two large through-bolts. As you withdraw it forward, the push-rods will be pulled from their location on the piston. There are two rubber gaiters too, so try to catch them before they disappear under the car.

An initial clean-up can be done with methylated spirits (wood alcohol). The top and end plates are removed and if the gaskets are in good shape they can be reused as they are not under pressure. However, most service kits contain new ones. As you remove the end plate, the pistons will normally pop out under spring pressure.  Under the piston is a dished washer, which will normally drop out under gravity or can be hooked out with a piece of wire. If the springs with their rubber seals won’t drop out of their own accord, it may be necessary to use the wire again. In the bore serving the brakes, there is an additional set of components under the spring. These provide additional control of the fluid flow in and out of the bore. With the spring should come a small metal piece shaped like a top-hat. It may also bring with it a rubber cup.  If it does not the cup will need hooking out along with a rubber ring that fits snugly at the bottom of the bore. The latter is the fiddly bit.

Inspect both bores. If they are badly worn or pitted, then the cylinders will need to be over-bored and sleeved with stainless steel. This is a job for a specialist machine-shop. If there is not too much wear or damage, a light honing will be sufficient to get them back to good condition. You will need a small honing device with two or three stones. Use lots of lubrication: brake fluid works fine. As long as only a tiny amount of surface metal is removed, the rubber components have enough spread to compensate for it.

If the body is rusty and the reservoir sludged up, the casting can be blast cleaned but be sure to mask off the bores. Paint the casting immediately or the rust will start again. There should be small holes in the bottom of the reservoir, one for each bore. This is how the fluid in is fed into the system.

Absolute cleanliness is necessary during reassembly and only brake fluid should be used for final cleaning but keep it off any new paint on the casting body. Take care to replace the extra valve components in the correct bore. It is the one on the right, looking down the bores. The pistons will protrude from the bores until pushed into position by the replacement of the end-plate.

Before replacing the master cylinder in the car, test its operation. Put fluid in the reservoir and work the pistons. The new rubber will make them stiff to start with but after a few strokes, fluid should be emerging from the tapped end holes.See the separate article about dealing with new components that stick and do not move freely. On the clutch side, the fluid will be sucked back in on the return stroke, but on the brake side, the non-return components should stop back-flow.

On reassembly into the car, the push rods need to be eased back through the end plate whilst holding their corrugated boots in position. Once the hydraulic connections have been remade, the system can be bled. With new rubbers, it can sometimes take a while for fluid to flow into the system. This is where a pressurised bleed kit can pay dividends because the pressure overcomes the reluctance of the rubbers.

Do not over-fill the reservoir or you risk spillage of fluid through the air bleed hole in the lid.

Naturally, after any brake work, a gentle road test is advisable in conditions where the brakes can be tested under increasing amounts of pedal pressure until you are satisfied that all is well and the system is leak-free.


When everything else is checked and OK, re-check the free movement at the pedal. Using hand pressure, the pedal should move about ½ “ down before you feel the pressure of the master cylinder piston. Adjust with a spanner using the hexagons  on the push-rod.

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