M52A2 brake problems

[German 5ton owner]

My Truck has brake problems and i dont know how to get this solved. 2 weeks ago i parked my truck for a paint job. After that i drove it out and the brakes applied full. The truck didnt move at all.
I thought this could only be the Hydrovac. thats why i changed the hydrovac and bleed the hole brake system.
After that i started the truck again. First the brakes worked but after reaching full air pressure the brakes applied completely again. All 6 wheelbrakes are applied. The brake only releases if i open the drain valve under the air pressure tanks.
The service side glad hand is ok and it vents.
What could be the reason for this porblems?
Did anyone ever had a problem like this?

 

[M543A2]

If you look down into the bottom of the master cylinder you will see two holes, one larger and one smaller. Check to see that both holes are open with a wire, torch tip cleaner, etc. The small hole being blocked caused this problem for us.
Regards Marti

 

[vtdeucedriver]

What did you find with this?

 

[German 5ton owner]

Today i istalled a new master cylinder. Now almost the hole Service brake system is new. Every wheel brake cylinder is new and also the airpack. After starting the engine everything is fine. But if I apply the brakes more than one time they do not release at all. The problem ist the same like before.
I just dont know what this could be. Whar is the task of the air governor? Could this be the reason?
Or are their other valves which could cause this??

 

[NDT]

The vented glad hand cover is in the front, correct?

 

[German 5ton owner]

Yes. I took it off. An it works.

 

[vtdeucedriver]

Yes. I took it off. An it works.

As in the brakes work?

 

[Robo McDuff]

Did you manage to find out what the problem was? There are several threads on M39 (the M5x series trucks) 5-ton brakes running right now. I am starting to work again on my M51A2, lost my oil.

I am not sure a problem in the air system could cause this.

Different question: I am restoring an M51A2 here in the Czech Republic, about 250-300 km from you. Where did you buy the Dot 5 hydraulic oil and the new parts? Would be could to know an alternative source, most of my stuff has to come from Reomie in the Netherlands. The Dot 5 here is very expensive, something like 16 EUR for 375 ml!

Do you knwo anything about the history of your truck?

Finally,

 

[73m819]

Did you VERIFY that the piston in the M/C goes all the back, sometimes a new m/c will need the linkage adjusted, WITHOUT the engine running, (no air) does the brakes release after being applied, if they do then the problem is in the airpack or the vented gladhand, could have a mud dobber nest in the gladhand / pipe or your new airpack is bad, that is not unheard of.

 

[German 5ton owner]

@Robo MC Duff. Yes i found out the problems that caused this. it was a mixture of everything including the compressor..^^