Help - Hot rear drums

[Bluesnailman]

Well, dont know the answer to the problem, but the answer to the photo is that yes, those are the one way valves that are fitted to drum brake circuit. I have them still fitted to my rear brakes though a servo and dont have your issues.

you could try your local motor factor and get a same thread connector and substitute these for something without a one way valve, and then you'd know. looks like a right chore though...

 

[sparkywig]

Those valves have to be fitted to drum brake circuits as they need some residual pressure in the system to work efficiently.
You can remove them if you have discs fitted though.

 

[Moseley]

Have you changed the springs in the rear drums? I wonder if now that you've confirmed the MC and hoses seem to be in good condition that you've gone full circle back to what you originally thought it could be - weak springs? Maybe they just don't have quite enough tension to overcome the one-way valve spring + the other hydraulic resistance. I know from fitting my rear shoes recently that it takes some real strength to pull the shoes into their location slots on the star adjusters as the springs are so stiff. How do yours feel when assembling the shoes?


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[markevo30]

Those valves have to be fitted to drum brake circuits as they need some residual pressure in the system to work efficiently.
You can remove them if you have discs fitted though.

Thanks Sparkywig. I've now read up on the residual pressure valves and you're right, they are required. They keep about 10psi of pressure In the system which primes the hydraulics keeping the shoes close to the drums which reduces pedal travel and improves the 'feel'. As there's no spring to counter this pressure when discs are fitted the valves should be removed otherwise the pads will drag on the discs.

 

[markevo30]

Have you changed the springs in the rear drums? I wonder if now that you've confirmed the MC and hoses seem to be in good condition that you've gone full circle back to what you originally thought it could be - weak springs? Maybe they just don't have quite enough tension to overcome the one-way valve spring + the other hydraulic resistance. I know from fitting my rear shoes recently that it takes some real strength to pull the shoes into their location slots on the star adjusters as the springs are so stiff. How do yours feel when assembling the shoes?


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No, I've not replaced the springs. Having done a lot more reading on the subject I'm starting to think that there's nothing wrong with the hydraulics. I was just about to tear out the guts of the residual pressure valves to try and cure the problem. I imagine this would have helped but it wouldn't have solved the initial issue. I'll order a spring kit today and give it a try.

 

[bluebay]

Had a very similar problem on my rear drums,after fitting new rear shoes they would bind after a couple of miles and get too hot to touch,if I cracked the bleed nipple they would free off.
Did all the checks you have including fitting new master cylinder,brake cylinders,re piped brake line to rear plus new braided flexi hoses,still had problem.Finally I got the grinder out and took a couple of mm off of the new shoes just on the face which pushes onto the pistons.so it appears when I set the brakes by adjusting the star wheels I could not of had enough clearance.Not had a problem since.That was a couple of years ago.Took me about a month of changing things and then trying it to get to that point though.
Phil.

 

[markevo30]

Thanks Phil.

I'm catching some rays in Menorca at the moment (still checking the forum though :msn4: ) but much to my wife's disgust I changed the springs the night before the flight and managed to get a short test run in and it seemed a little better. I'll give it a proper run when I'm back in Blighty. If it's still running hot I may give your suggestion a go as I'm running out of ideas.

Mark