Failed MOT - Rear Brakes

[936cbpminor]

Failed MOT on both rear brakes. Station says it is almost although they are not there!
Good pedal they say so no leakage. All metal and flexi pipes changed for last year MOT and it passed with flying colours. Front brakes excellent and pass easily (no pull to one side)
Now I have taken road wheels off and drums. slight dampness between drum and hub assembly.
and there is a whiff of EP90 there does not appear to be any dripping.
There single countersunk screw that holds the hub which I managed to get a tightening turn out of!!
Now do I assume that the gasket axle shaft (DIF150) and/or oil seal hub (DIF149) could have failed?
The gasket seems easy enough to replace but what about oil seal?
The purpose of the oil seal is self explanatory but is the gasket a belt and braces second seal?
I appreciate if it is any or all of these it will be a decontamination of drum plus new shoes.
There does not appear to be any hydraulic oil leak.
Any help appreciated.

[bmcecosse]

Check if the pistons are moving when you pull the handbrake - and when you press the pedal. Are the shoes actually 'wet' with oil? There is a drain hole in the backplate - make sure it is clear on each side. The tightness of the single screw is not important - the wheel studs clamp it all together.

[936cbpminor]

Hi bmcecosse. Many thanks for your help here.
I have done as you suggested. The handbrake operates the pistons and, although uneven as the MOT station said, do lock the drums. Now the foot pedal whilst offering resistance does not lock the drums. The pedal does feel good i.e. not spongy and does lock hard. MOT report says front brakes are excellent. So it seems that fluid is going to the rear but not enough to actually lock the brakes on. They all do free when you release. Could it be they are so far out of adjustment on the snail?
To answer your other questions the shoes are not wet and the hole in the backplate is clear. As an aside, is it worth leaving the gasket alone?

[bmcecosse]

Yes -leave the gasket alone... So to the old problem of rear brake adjustment ... first slacken off the cables at the lever - then adjust up the brakes on the snails - does the footbrake hold them now? If so - lightly tighten the cables again to put the lever where you like it. Over-tightened cables prevent the internal hydraulic cylinder moving... Of course - it may have got stuck there, but you can only try!

[mike.perry]

The rear brake operates a piston which in turn pushes up on the top piston which is the one operated by the hand brake so it could be that the hydraulic piston is not operating as it should.
Check that the handbrake lever on the piston is operating freely, push on the lever agaist the pressure of the brake pedal. Also check that the handbrake cable is working properly, apply oil or grease to the inner cable where it emerges from the outer cable.
With one drum removed press hard on the brake pedal which may free the piston. If all else fails buy a new cylinder.
The set screws are there to retain the half shaft and brake drums, they are not there to tighten the drums, this can be done with a couple of wheel nuts

[936cbpminor]

bmcecosse and Mike.Perry - both, thank you for your knowledge here. I shall be out on the weekend and do just this. I may have unwittingly caused myself the problem by overadjustment of the handbrake. Anyway, I shall set to.
At the moment rain stops play in 'Sunny South' - not as the Southern Railway would have you believe for the sunshine - Sorry bmcecosse, a Bluebell Railway fan here as well!!

[bmcecosse]

Some of the Bluebell lads come up to Bo'ness each year and 'run' our trains for us...but I've not made it down to the Bluebell..

[mike.perry]

The handbrake should be released and the cables slack when the brakes are adjusted.
After adjusting the hydraulic brake circuit fit the wheels and jack the rear wheels clear of the ground.
Apply the handbrake and check that both wheels are locked. Release the handbrake one notch and check the wheels have equal resistance. Adjust the handbrake cables if necessary.
The rear brakes should now be in balance for the brake test

[bmcecosse]

And the handbrake should lock the wheels at 20 mph on a dry road.

[936cbpminor]

Big thank you to bmcecosse and Mike Perry.
A half hour spent under you guidance and the car stops like a good 'un.
Handbrake is balanced and just peachy.
Thanks for your help.
Mr MOT Man - over to you!!!!!

[bmcecosse]

Good job - and Good Luck!