The MGA With An Attitude

At 05:56 AM 12/17/04 -0700, Phil McCormick wrote:
".... left rear break drum. It is stuck on and won't come off the break shoes. .... Will heat help?"

Heat is a last resort. Start with the simple things first.

Plan A:   If the drum is worn it can have a ridge inside at the open edge hanging onto the shoes. You need to rotate the drum until the access hole in the outer face lines up with a large slotted screw in the adjuster. This will be slightly below the horizontal centerline at the back. Rotate adjuster screw anti-clockwise (click, click, click) until it hits solid stop, possibly as much as 1/2 to 3/4 turn. This will allow the shoes to retract to clear the wear ridge so the drum can be removed.

Plan B:   If the drum turns freely but will not release from the center studs, be sure you remove the two flat head retaining screws. If it doesn't come off immediately with a good solid pull, try a little shock from the back. Catch the flange on the edge of the drum with a flat end punch, pointing the punch generally outward away from the centerline of the car, and give it a good whack with a two pound hammer (lots of weight and inertia but not too much speed). If it doesn't pop loose immediately, don't overdo the effort, as you might break the thin flange off the drum. Simply breaking off a piece of the dust flange is generally not detrimental to function of the brake drum, as long as you don't crack or deform the inside friction surface.

brake drum puller Plan C:   If that doesn't break it loose immediately, you may need a brake drum puller. This tool looks like a large but light duty three leg gear puller see here:
JC Whitney brake drum puller
Eastwood Products brake drum puller

brake drum puller Hook this on the flange of the drum at three equally spaced points, with the center screw pressing on the center of the disk wheel axle flange or inside the center of the wire wheel hub. Tighten the manual screw to pull the tool tight. This will pull the drum shell outward, slightly deforming the outer flat face of the drum with a spring type preload. Do not over torque the puller tool, or you run a risk of permanently deforming the drum. Use strong wrist action on the screw, or a very short wrench if it your wrist is weak. Do NOT use a big wrench as shown in the second picture. Also do NOT strike it hard from the back as is implied by position of the hammer in that picture. The puller tool should be pulled up moderately tight, and you should be able to rotate the drum and axle shaft with the tool attached.

With the puller tightened up snug, use a two pound hammer to strike the drum radially inward (gently) as near as possible in line with the plane of the outer face. This will put a solid inward radial shock on the flat face of the drum with very little stress on the outer shell. Just don't hit the center of the outer shell or the thin dust flange. Keep the impact in a radial direction at the outside shoulder of the drum. This is intended to shock the center guide hole and/or the holes around the studs in the radial direction to break it loose from the pilot diameter or from the studs. This will work even if there is zero clearance in the pilot diameter, if it is held with rust, or even if it has a slight interference fit. The impact will break the drum loose from the pilot diameter, forcing it ever so slightly radially. Rotate the drum in 1/3 turn increments, continuing to strike it radially with the heavy hammer. The center pilot will eventually (perhaps gradually) let loose and allow the preloaded center of the drum to spring outward. Sometimes it lets loose with a bang, sometimes only a little at a time, but this should always work with a little patience. If not, then you may have to think about applying heat to the face of the drum, but I have never seen one stuck that tight.

Plan D:   If the car was parked for a long time with the hand brake applied, the shoes can be stuck so it will not rotate at all. First check that the cable is not stuck. Lower the hand lever to relax the cable. get under the car at the back, just at the rear side of the axle housing. Grab the cable jacket (not the bare cable) and pull hard to one side. This should pull the center cable tight at the end(s) without pulling at the front. Another good sideways yank should pull the cable out at the output end, so when you let go of the jacket the cable will have slack near the brake backing plate. Check to see that the lever will move. Push it back toward the backing plate if it sticks. Check to see if the wheel (brake drum) will rotate. If it will rotate, revert to Plan A.

Plan E:   If you have slack in the cable, but the drum is still stuck and will not rotate, then the shoes are likely stuck to the drum. When the adjuster access hole is not aligned with the adjuster cam, there is a high probability that it is aligned with part of the flat web of a brake shoe. If so, then start by inserting a fat punch and give at a good whack with a hammer. That may break the one shoe away from the drum. If that works then the drum may turn a little before the other shoe hits mechanical stops. You may need to hit it pretty hard. The drum will flex a little, but the backing plate will flex farther and easier, so a good whack on the shoe should break it loose from the drum. Put lug nuts on the wheel studs to prevent damage to the threads. Try a long lever between the studs to rotate the drum by force. If it works, revert to Plan A.

Plan F:   If you're still stumped at that point, things get a little more desperate. Remove the nuts (on backing plate) from the "abutment" opposite the slave cylinder. Give the studs a little tap to pop the abutment loose from the backing plate. This will allow the top ends of the shoes to pull away from the backing plate when you pull on the drum. Get a drum puller snugged up on the drum (if you have one). Insert a BIG screwdriver between the drum and the backing plate near the abutment and pry them apart a bit. Maybe give the abutment studs a little tap again if it hasn't broken loose from the backing plate yet.

As you pull the drum the backing plate will come under tension at the slave cylinder, but not at the abutment. This will put a load on the end of the shoe contacting the slave cylinder while allowing the opposite end of the shoe to move away from the backing plate. A drum puller can help here as it can keep a firm and even tension on the drum. Give the accessible shoe a shot with the punch through the adjuster access hole again. That gives a shock to the backing plate separate from the drum. Use a heavy hammer, about 2 pounds, to give a moderate thump to the brake drum, same as if you were trying to free the drum from the hub. Hit it in a radial direction on the edge near the front in line with the face flange. Do not hit the flange on the open edge of the drum. Give it a good solid rap and repeat in various places around the drum. With luck the combination of tension, imbalanced pull on the shoes, and shock in various directions might break it loose. At the very least it should break the drum loose from the hub. If it works, revert to Plan A.

Plan G:   With cable loose but drum stuck tight and will not turn. Put the wheels and tires on the car. Lift the rear with a wheeled floor jack under the differential, and haul it out to a place where you have a few car lengths of space ahead of the car. Get a helper or two. Push the car forward as fast as you can within a distance of several feet, and drop the jack as quickly as possible while it's still moving. With luck the weight and inertia of the car may turn the tires to break the drum loose from the shoes. With an advance assumption that this will work, be fully prepared to stop the forward motion of the car when it rolls. Someone in the driver's seat may hit the brake pedal (if it has hydraulic function). Do not depend on the hand brake working. If nothing else, you and the helper(s) may have to stop the roll by hand, so be advised not to do this on a steep grade unless someone is in the seat with hands on the steering wheel and having plenty of roll out distance. If this works, revert to Plan A.

Plan H:   If this does not work, and the drum is still stuck to the shoes, you may be into the realm of innovation and creativity, which may depend on your experience and tools at hand. If you are going to apply heat to the brake drum, do it in a well ventilated area and have a fire extinguisher handy. Leather gloves are also a good idea. You will need to heat the drum evenly all the way around at once. Being a large part you will need a large torch. A single hand bottle propane torch likely won't do it. Two or three propane torches used simultaneously might work. One oxy-acetylene torch with a large tip works best, but keep moving the torch around the drum to heat it evenly all around the outside. By the time you get the drum anywhere near red hot the shoe lining material would likely be smoking profusely. That should be more than enough to get the shoes to let loose from the drum. Use this in conjunction with Plan E (long lever to rotate). Then let it cool and revert to Plan A.

Plan I:   If all else fails, use the oxy-acetylene torch to cut the brake drum into about four pie shape sections and knock it loose from the shoes with a heavy hammer. This is followed by cooling, cleaning, painting, and the purchase of all new mounting hardware and shoes, maybe a new slave cylinder, and of course a new brake drum. We all hope it never has to go as far as Plan I.

Plan J:   This is one of the slickest tricks, but only works on front drums of an MGA 1500. If the shoes are stuck to the drum, and the drum will not turn with any force, and you cannot get the adjuster to budge, there is still a way to disassembly. Disconnect the hydraulic lines. Take the bolts out of the brake cylinders, and tap them through the backing plate. The drum will come off with the shoes, springs, cylinders etc. Once off it is easy to get the internal parts loosened and removed.

Addendum, January 10, 2010:

Plan K:   Recall the first note at top of page, "Heat is a last resort". I should have mentioned that penetrating oil might help if the drum is stuck on the center pilot diameter. The follow up comment is, do not use an open flame torch in conjunction with penetrating oil (fire hazard).

Now I have another note from Dan Voigt in Gladstone ND. He suggests:
"One old slick trick that really works is simple soapy water mixture. Unstuck my basket case rear drum in 5 minutes (I barely touched it). I use on rusty bolts, hinges, tires stuck to rims, use for drilling steel. It's cheap, it works, and no oily mess".

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