Y Type Brakes in OLD AGE.
Nothing on old cars is ever simple! For instance there are two completely different braking systems fitted to Y Types. First, read the workshop manual section ‘L’, ‘Brakes’ for your model. Sadly I have to add the following H&S, even though you will all know it! Ensure you chock a wheel when working on your car and that you use an axle stand in addition to a jack. Oil can affect your skin so please use a barrier cream. It is easier to loosen wheel nuts with the tyre on the ground, before you jack it up. Do not get any oil or grease onto the linings or the drum’s face.
The YA adopted the brakes from the TA, TB and TC. As these MGs were all about the same size, this was a logical thing to do and helps the spares supply problem. MG used Lockheed brake systems from the Morris parts bin, so the YA has almost identical brakes to the Morris Ten/4 Series ‘M’ and the van, Wolseley 10/4 and very similar brakes to the Morris Eight Series ‘E’.
The YB uses the brakes from the TD which are more modern. Other Nuffield cars using virtually identical brakes are the Wolseley 4/44, Morris MO Series, Riley Pathfinder and Wolseley 4/50 and 6/80. Brake drum sizes do differ as dose the design of the master cylinder, but the bits inside are the same.
(Whilst the YA/YT and YB look superficially the same, there are quite a few differences that will trap the unwary. There should be a mini-article on these pages showing what was different.)
That fitted to the YA and YT is a pre-war ‘single-leading-shoe’ drum brake system, which simply means that each front brake drum only has one brake cylinder with a piston either end; one is pushed on so that the drum actually ‘drags’ the leading shoe on harder, and the other ‘trails’ and is not as efficient. When driving backwards and braking, the shoes will of course, swap over their actions. The pistons inside the brake drum cylinders that force the shoes apart to operate them, are worked by hydraulic power. That is an oil (brake fluid) is used inside pipes to work the system from a ‘master cylinder’ worked by your foot pedal. This bigger ‘master’ cylinder is worked by the foot pedal which incorporates a reservoir. The oil used is a vegetable based oil and will remove paintwork in seconds, so be careful. If you do spill any, dilute it immediately with lots of water. You will need a workshop manual to work on this system, these notes are only for explanation and describing old-age faults.
STICKING BRAKES;- One very easily cured fault is the need to ‘ease’ the pistons in the wheel cylinders about every three years. Sitting unused in a damp garage over the winter often raises this one. The YA/YT cylinders are of cast iron and do not suffer as badly as the YB alloy ones do with corrosion. Because the seals are of an umbrella type, it is possible to remove the steel pistons without disturbing the hydraulics. The pistons ‘stick’ and hold the shoes against the drum, causing hot brakes, extra fuel consumption and wear. The cause is the dust inside the drum from the brake linings, moisture in the air and corrosion due to lack of use and a bit of dis-similar metal electrical corrosion. If you jack up a wheel and find it difficult to rotate that wheel, the bet is that the wheel cylinder pistons need cleaning; it is not ‘returning’ fully into its cylinder. Adjust the brakes away from the drum by using the big nut adjusters behind the back-plate (see diagram). Remove the drum, remove the shoes, DO NOT BREATH IN THE DUST as it may contain asbestos. I wear one of those little paper masks and use an old battery-powered car vacuum cleaner.
Modern bonded shoes are safe but if your linings are riveted on, they may well be old asbestos based ones. If you cannot get the shoes off the back-plate, you have forgotten to remove the circlip from the lower pivot. Put a rag over this circlip as you remove it with circlip pliers, they have a habit of pinging off into orbit.
Carefully prize out the piston and clean all that muck and rust from it. Carefully clean out the inside of the cylinder, use brake fluid on a rag in the cylinder but you might need emery cloth for the piston. Lubricating the piston and cylinder with SILICON grease, reassemble it all. Do not use WD40 or mineral based grease as this will rot the seal and contaminate the brake fluid. Work a little oil into the snail-cam adjusters. Getting the shoes over the cylinder needs some strength with that important spring. Do not forget the circlip. Remember there is a piston both ends of the cylinder. On the YA/YT the single brake shoe spring goes in front of the shoes. On the rear axle there is the complication of the handbrake cables, but careful study will help you. It has to be said the YA-YT handbrake system is far superior to the later YB system, as you will see. Refit the drum. Re-adjust the brakes using the big nuts on the back-plates until the drum locks, then ease off one ‘flat’. Check the drum spins easily.
If you carried out this little job properly, you did not need to touch the brake pedal. Silicon grease can be found at electrical tradesmen dealers. It is inert so will not affect the brake fluid. Even so, in about 3-4 years time you will need to do this again. As you are under the car, fill the handbrake cables full with grease using a pump-grease-gun, until it oozes out of the end, but keep grease off the linings. There is a nipple at the cable’s central point.
Where it all goes wrong is when you cannot get that piston out! Then you need to use the brake pedal to force it out. This means the seal will travel over the corroded/mucky part of the cylinder. Then it is adviseable to have a new set of 6 seals handy to fit and clean out all four cylinders (2 each on the front, one each at the rear). One piston will pop out using the brake pedal, the other will remain. This one can be pushed out from the now open other end. This also means you will have to bleed the brakes once they are all re-assembled! Watch out with that brake fluid. Bleeding the brakes requires two people, one to operate the pedal and top up the reservoir, the other to open and close the bleed nipples. That is when it really goes tits-up when the bleed nipple shears off…If your brakes cylinders are this bad, you may required new ones. But before you do that, it might be possible to get the sheared off bit out using things called ‘easy-outs’, available from any decent tool shop. They are twisted so when you force them into the old bleed nipple, they actually undo it.
And before you attempt any of this, read the Workshop Manual.
The brakes on the YB are completely different to the YA/YT other than in their drum’s internal diameter. Nothing is interchangeable. Whilst on the earlier cars the brake drums can be removed for servicing on their own, those on the YB are part and parcel of the wheel’s hub, so a puller will be required. That is, the wheel bearing and brake drum are a one piece casting. It will take twice as long to do our YB’s brakes! The twin-leading shoes of the front brakes means the YB stops better than a YA travelling forward, but not in reverse! Each brake shoe on the front wheels has its own brake cylinder and so both are ‘leading shoes’ and get a bit of ‘servo’ action by the drum’s rotation (see diagram). The shoes are held onto the back-plate by a small pyramid spring. To remove them, use pointed nose pliers, push in hard and turn 90 degrees and they will pop out. When refitting ensure they are locating into the slot behind the shoe, because if they fall out they will gouge great big grooves in your drums. DO NOT BREATH IN THE DUST.
The rear brakes are secured the same way but there is only one combined hydraulic/ handbrake-cable cylinder. There are two pistons inside this alloy casting, the innermost one is the normal one with an umbrella seal behind it. The outer one is operated by a little lever that the handbrake cable pulls. To permit the shoes to align themselves in the drum as they wear and to allow the handbrake to work both shoes, the whole cylinder slides in a big slot in the back-plate. This cylinder is often seized solid in the back-plate. Waggle it back and forth to free it and put a tiny amount of grease into the slot. From the back this slot is sealed with a rubber dust cover that is not very efficient, so add a bit of grease here. Whilst you have the grease gun handy, fill the handbrake cables full until grease oozes out of the cable end above the rear springs. There is a grease nipple at the cable’s centre point. Note how the YB’s handbrake system is nothing like that of the earlier cars.
The adjustment of the YB’s brakes is through a hole in the drum, using a ‘snail-cam’ worked by a screwdriver. If you fit the wheel with its hole over that of the brake drum’s, you can adjust the brakes without removing the wheel, just the hub cap (knave cap).
Like the YA the wheel cylinders stick after a while, but on the YB it is a lot worse. As above, loosen the wheel nuts AND in the YB’s case, after removing the split-pins, the front wheel bearing nuts and the rear axle half-shaft nut, then jack up the car and fit an axle stand (see photo). Note the LH front wheel has a wheel bearing nut with a LH thread, and the RH a (normal) RH thread. Both rear axle hub nuts are normal RH threads. Wind back the snail-cams to free the brake shoes, and using a puller, remove the hubs. The brake cylinders are cast aluminium alloy, the pistons are mild steel, the seal is synthetic rubber and the fluid a vegetable oil. This all adds up to quite a mixture of metals, and with the oil acting as an electrolyte, those steel pistons corrode easily (becoming the sacrificial anode). As on the YA the pistons can be removed without disturbing the seal. If the pistons will not come out, and do not lever them too hard or the spot-welded dust covers will break off, on the front ones you can secure one cylinder with a ‘G’ clamp to hold its piston in, whilst pushing the other out using the brake pedal. Take care not to go too far or the seal will pop out as well. To clean inside the cylinder, force the seal back with your thumb. The insides of the cylinder can be cleaned with a rag with brake fluid on it (keep that well away from any paintwork) on a screwdriver. The piston may need light cleaning with emery cloth. Lubricate all of this with silicon grease and re-assemble. Keep the grease off the brake linings. On the YB the two brake shoe springs go behind the shoes. Do not forget the snail-cams that live ontop of the pistons, they will be a pig to refit as well, especially if you fitted the shoes the wrong way around; the locating hollow goes over the wheel cylinder’s piston end. Refitting the pyramid springs is the opposite of removing; push their hooked end into the slot through the hole in the shoe, and turn 90 degree towards the outer edge of the back-plate.
Re-assemble the brake shoes, fitting the pyramid springs. Fit the drums and torque up the hub nuts and fit new split-pins; you have to align the slots in the castellated-nut with the hole in the stub axle/half-shaft. Adjust the snail-cams until the brakes lock, then come back one click. Check for free rotation of the wheel. On the rear brakes, check the handbrake cable is loose and not taught. Sometimes lazy owners adjust the rear brakes by winding up the two nuts on the handbrake lever in the car. If it is taught, loosen off these nuts and re-adjust the snail cams as above. Then adjust the handbrake lever’s nuts.
Warnings;- Note that some early YBs use 5/8”BSF front hub nuts and later ones UNF nuts. All YBs use UNF threads on their wheel nuts and some YAs. Most YA and YT use BSF wheel nuts. UNF nuts have a line of little circles on them to identify them. YA wheels will not fit a YB, the hole centres are different. The YB has a Nuffield Hypoid rear axle (all UNF nuts, see nut identity diagram below left.) where as the YA/YT uses a Morris Spiral-Bevel rear axle (all BSF nuts).
YA, YT and YB.
Check that the handbrake cable is not worn, the twisted wire cable will have broken strands (an Mot failure area). Check that the brake linings on the shoes have at least a millimeter of lining above the rivet heads, or if later bonded ones, they have about 1.5 millimeters thickness. If you get squealing brakes with new shoes, file off their leading edge with a 45 degree ‘lead-in’. Always test the brakes before you go for a run after working on them, it only takes a second as you pull away. Double-check you have tightened the wheel nuts. New shoes will require ‘bedding-in’ and may not feel very efficient for about 50-100 miles. Once bedded-in they will need adjusting again, (this is not a modern car with self-adjusting brakes!).
Article supplied by Neil Cairns.