Rear brakes stuck

[guusvanloo]

Hi all,
My P5b hasn't run for years. Now the rear brakes are stuck. I removed the wheels trying to remove the drums but can't move them at all. Any tips please?
Thanks!
Guus (Belgium)

[enigmas]

Jan 7, 2024 9:12:38 GMT guusvanloo said:

Hi all,
My P5b hasn't run for years. Now the rear brakes are stuck. I removed the wheels trying to remove the drums but can't move them at all. Any tips please?
Thanks!
Guus (Belgium)

Well hopefully you didn't park the car outside, in the open air, on grass, for however long the car hasn't been used. If you did moisture and condensation will cause more issues than the drum brakes being locked up.

Freeing-up the Rear Drum Brakes:

1. Back off the rear brake shoe adjusters. This will relieve any residual clamping force that the shoes may be exerting on the brake drums.

2. Disconnect the rear hydraulic brake hose.
The inner liner can degrade over time and fail to release hydraulic pressure to the rear shoes. A faulty/aged brake hose will hydraulically lock the shoes against the brake drums.

3. If the shoes are still frozen to the brake drums after the above methods have been tried it may be time to use "heat" to release the bond between the drums and the brake shoes.

4. If you have access to a Propane or MAP gas torch heat the outside circumference of the brake drum evenly until it is quite hot. The brake drum should expand slightly to relieve the contact binding situation with the brake shoes.

[Phil Nottingham]

After loosening the adjuster right back use the inbuilt drum puller. This is one of the 3 drum retaining screws which need to be removed. Screw one into the threaded hole near the centre after oiling it. Use the right sized driver and tap the drum sides with a hide hammer hard while doing it

[MK IA Norway Viking]

I just went through the same exercise. In addition to loosening the brake shoes with the rear brake shoe adjusters (a big adjustable spanner / wrench is best, for the shape of the adjuster is square) undo the hand brake rod. If the hand brake has been activated when you parked the car (or since) the brake shoes will be stuck on the brake drum.

As Phil says, undo the 3 screws securing the brake drum and use a hammer to gently / medium force hammer onto the drum in various positions along the edge of the brake drum that face inwards.

Good luck in freeing up the brake drums.

PS - there is no flexi hose for the rear brakes. This is only for the front brake/caliper. The rear brakes have pipes and you are advised to replace these considering the age of the car and that it is rusty in the rear area.

[lagain]

While the brake pipes that run along the rear axle fix directly to the cylinders on the P5b there is a flexible hose from the body to the axle. That will need replacing. The most likely problem is that the connections will be difficult to undo which will mean replacing pipes.

[enigmas]

Jan 8, 2024 11:37:59 GMT MK IA Norway Viking said:

I just went through the same exercise. In addition to loosening the brake shoes with the rear brake shoe adjusters (a big adjustable spanner / wrench is best, for the shape of the adjuster is square) undo the hand brake rod. If the hand brake has been activated when you parked the car (or since) the brake shoes will be stuck on the brake drum.

As Phil says, undo the 3 screws securing the brake drum and use a hammer to gently / medium force hammer onto the drum in various positions along the edge of the brake drum that face inwards.

Good luck in freeing up the brake drums.

PS - there is no flexi hose for the rear brakes. This is only for the front brake/caliper. The rear brakes have pipes and you are advised to replace these considering the age of the car and that it is rusty in the rear area.

MK1A Norway Viking, unless the complete differential assembly is bolted solidly, rigidly and directly to the car's monocoque frame allowing no rear suspension movement at all, there has to be a flexible hydraulic line included in the hydraulic system to the rear brakes. An example of this would be the rear suspension of an E Type Jaguar with inboard rear brakes or similarly a De Dion rear suspension system as fitted to a Rover P6. Where both the differential carrier and rear brake assemblies are bolted directly to the body.

Consider also that on a P5 due to the rubber mounted front subframe, there is a "loop" incorporated in the hydraulic brake line as it transitions from the engine/trans subframe assembly rearwards to the body. Without the loop there'd be a possibility of fatigue fracturing the brake line due to the slight movement between the car's body and the front subframe. This possibility is further aggravated if the car has well worn and rotted subframe bushes.

[Mike’S-a-loon]

Absolutely, Vince. The single rear brake flexible hose connects close to the centreline of the rear axle to a T junction which joins solid pipes out to the rear cylinders.

Below the info for the part from Wadhams:

[MK IA Norway Viking]

It's correct that there is a flexi hose from the body on the right hand side in front of the rear axle. It's purpose is to take up rear axle movement without stressing a brake-pipe.

The talk on this thread was about removing the rear brake, and it was suggested there is a flexi hose arrangement - this is relevant only if the  flexi hose is showing signs of wear, but not to alleviate any brake-fluid pressure. 

Taking off the brake pipes from the brake cylinders could be a sensible thing to do if the objective is to ensure there is no pressure acting on the brake shoes. I believe removal of any brake fluid pressure should be done by disconnecting the brake pipe on each brake cylinders since it is the closest point to a (possible) sticking brake shoe.

[MK IA Norway Viking]

... should read brake DRUM

[enigmas]

For those that have never encountered a faulty brake hose.

The brake hose you see in the pictures below is from an MGB brake caliper. The inner lining of the hose has degraded to a point that it will not allow the brake fluid to flow back to the master cylinder once the brake pedal is released. Fluid will flow forward under hydraulic pressure, but the return of fluid during brake release is compromised.

To prove this, I removed the hose and attempted to pass a thin rod of TIG welding wire through the hoses internal liner. Under no amount of force would the wire pass through the hydraulic hose's internal liner.

An old degraded brake hose will maintain considerable residual pressure on either a brake caliper or a brake drum assembly. Hence the advice to disconnect the brake hose. Disconnecting a brake line union at the slave cylinder will relieve hydraulic pressure on a brake assembly but it won't resolve an issue that may stem from a degraded brake hose.

All components will eventually fail if not serviced, checked or replaced on occasion.





In the images directly below, both pistons are clamped yet cannot be forced under pressure of the clamps to return inside the caliper bores. Note that the hydraulic hose is still attached but one end is open to atmosphere. The cause is the constricted internal liner of the brake hose.