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Munga brakes binding help!


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Hi all, I’ve recently purchased a lovely Munga 8 which has undergone a full but economical restoration over the last decade or so. Overhauled engine running sweet and new brakes all round. After about 10 minutes of driving the brakes are getting so hot that they are binding to the point where I can’t really drive. I’ve taken the drums off and the pads, pistons, hoses etc are all brand new. I’ve backed off the pads to the minimum setting yet they still bind after a few minutes of driving. When cold, you can spin the wheel freely but when hot they are impossible to turn by hand. 
has anyone had this issue with their MV and what was your fix? 
many thanks, MikeB9BC6354-B5B5-424D-8E4B-127C16140EF5.jpeg.3348acc950dea2eb51ae820adbf0ce30.jpeg

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I assume all 4 brakes are binding.  It seems as if brake fluid is being pumped to the brakes but not returning.  In addition to Richard's suggestions, check Flexi hoses common to all 4 wheels.  Internal failure can happen (and has happened to me) in this way. Easily checked by pumping brakes till they bind then crack brake end of Flexi hose and see if they release. Clearly bleed properly before going on road.  Good luck. Toby

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Thanks guys, I will attempt these fixes tomorrow and report back. I’ve had a few people recommend that I sand off a tiny bit off each pad as when I put the drums back on there is always a slight abrasive sound. Baring in mind that they are wound in to their minimum setting. When cold it’s not enough friction to restrict movement by hand by any means, but I’m guessing when it gets hot it’s all expanding to cause the binding? Can this sort of light friction cause this?? 
I am liking the idea of the fluid not returning to the master effectively because when the brakes start binding up, I notice the pedal won’t depress very far at all. Does this symptom make sense to you guys? 
cheers, Mike 

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Hi all, I’ve checked the master cylinder and it’s all clean and not overfilled. The breather hole is clear and the fluid return hole is clear. The munga is cold and the brake pedal moves a good three inches with increasing pressure, when released I can see a little spurt of fluid as it returns rapidly to the master cylinder reservoir. So I can only presume all is well in this department. 
I will carry out Toby’s last suggestion about cracking each brake end hose when brakes depressed so see if it releases. After that I can only think it’s a case of taking a tiny bit off of each pad to gain the desired clearance from the drum and then re set to grab at a decent pedal position. 
Please keep the suggestions coming. Many thanks, Mike 
 

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The brakes should not be binding that quickly through heat.  If I understand correctly, then they are OK from cold, but bind after a small amount of use, hence searching for a one way valve type of effect. Besides, a hot drum ought to expand out more than in.  Have you checked the old shoes and done a size comparison?

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One more possible check to make, with out driving if you pump the brakes do they lock up?  What I'm looking for does it have self-adjusters and did they get mixed up?    Just looking for something unusual that would explain the problem.

As TJSB suggested looking for a one way valve effect, I've had this happen with flexible brake lines from two different causes internal failure and from being sharply bent.  As someone else suggested the test for this is backing off a bleed screw when the brakes are locked up.  If the brakes release then cause is in the hoses, line or master cylinder.

Keep us posted on what you find.

 

PS I've had this happen out of the blue with a late model regular car.

 

 

 

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Hi all, sorry for the delay in updating you. So I took her for a short drive and predictably the brakes bound up so I immediately jacked her up and cracked a bleed nipple and all four wheel simultaneously freed up! So I checked the lines (all of which are new) for sharp bends and fluid none. I can’t find any one way valves either. 
however the master cylinder push rod was set very far in so I undid the locking nut and wound it back out about an inch which seems to have made a big difference. I wonder if the piston wasn’t moving back enough to allow fluid to return as fast as it gets sent down the outlets? I only had a very short window to carry out a test drive so couldn’t really get a true representation but I’ll go for another tomorrow and hopefully she rolls freely. 
thank you all so much for the advice so far!

cheers, Mike 

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1 hour ago, Mike Maddams said:

Hi all, sorry for the delay in updating you. So I took her for a short drive and predictably the brakes bound up so I immediately jacked her up and cracked a bleed nipple and all four wheel simultaneously freed up! So I checked the lines (all of which are new) for sharp bends and fluid none. I can’t find any one way valves either. 
however the master cylinder push rod was set very far in so I undid the locking nut and wound it back out about an inch which seems to have made a big difference. I wonder if the piston wasn’t moving back enough to allow fluid to return as fast as it gets sent down the outlets? I only had a very short window to carry out a test drive so couldn’t really get a true representation but I’ll go for another tomorrow and hopefully she rolls freely. 
thank you all so much for the advice so far!

cheers, Mike 

The pushrod should generally have a small clearance of approx 3mm or so

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Displacement of the master cylinder pushrod is worth investigation , as you said. Especially since you said that all four brakes freed off when you cracked a bleed nipple.

Edited by John F
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Hey chaps, so I took her for a good drive to a neighbouring village this evening and all was good with the brakes. No binding that I could tell and I’m so pleased. I’m not saying I’m out of the woods with this one as I’m sure there will be something I have to deal with but as a runner to the local pub, she’s a goodun! I’ll chuck some fuel in the Jerry can and go for a longer drive as soon as I can and then we’ll really know if the issue has been resolved. Until then, thank you all for the support and I couldn’t have done it with you all. 
kindest regards, Mike 

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Hi Mike, In MUNGA practice it often happens that the brake hoses swell. The force on the pedal is enough to generate the brake pressure, but it reverses very slowly or hardly at all. The result is this Brake drum gets hot. However, this will not usually be the case on all 4 wheels at the same time! That would be a very big coincidence.
If all the wheels get hot after a short drive and several braking processes, the brake fluid will no longer flow back into the master brake cylinder. The adjustment rod is screwed in too far.

So see page 42 repair manual, for example on the DVD from the MUNGA IG on c://Munga-Doku/Repair-Manual/Repair-Manual.htm

If none of this helps, please try the following... Driving for a while without braking - what happens then? I hope I translated it clearly.

Ullrich

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I had the same problems about 15 years ago. It was also the master cilinder piston blocking the return port.

 

About your jerrycan....be sure there isn't rust or debris in there or you may clog your carb.

 

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Indeed I have found the cylinder position  to the the issue, after winding it out I’ve not had one single issue and the braking is still effective. 
 

thanks for the advice on debris in the can, I have been as careful as possible to check the inside and it seems ok. I am however always looking for even cleaner Jerry cans. 
 

cheers, Mike 

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