m35 master cylinder compensation port

[7-ton Rolex]

Good Luck 7ton

Take apart and clean out or replace defective parts.

Thank You !!

 

[rustystud]

When I read the part about "removing it" I had assumed he meant eliminating the hole to remove the problem. Now since there is debris in the system it needs to be cleaned out.

Also I forgot to add last night that if this hole has not caused problems for the last 3 to 4 decades, it is not the problem now. The problem is gunk in the system like I said earlier.
Did you replace all the flexible hoses when you did your brake system ? They can rot from the inside out. Leaving small particles of rubber to clog small orifices. There is four flexible hoses on the Deuce. Three on the front axle and one on the tandem system. All should be replaced. They only last for about 10 years according to most all brake parts manufactures. Of course most vehicles still have the original ones installed.
But getting back to the original question, I would never modify an original brake part unless I knew absolutely that it was defective. Even then I would most likely just replace it. The liability doing such a thing would be horrendous if you ever got into an accident.

 

[7-ton Rolex]

yes I did ,royal brass and hose made them for me they are a half an hour from me but seems to me that the hoses are pretty far downstream from the master cylinder but they have been changed incidentally the right rear wheel cylinder would make a slight hum when I backed up after I did my brakes and found out the steel brake line was full of gunk so I replaced the steel lines as well ,it will throw you through the windshield now but every couple of months the small hole will squirt to the side when you take the cap off and the pedal is hard and after I clean it out it makes a vertical fountain when you barely push down on the pedal with your hand I am going to take it off and drill it out maybe this evening ,then I'm going to tackle the lip seals in my air pack to stop the fluid loss through the slobber tube I'm thinking about putting an O ring inside the lip to strengthen the actual lip so it will have more force against the bore ,anyone done this to theirs I need your thoughts please ,I have the short airpack.thank you guy's

 

[rustystud]

yes I did ,royal brass and hose made them for me they are a half an hour from me but seems to me that the hoses are pretty far downstream from the master cylinder but they have been changed incidentally the right rear wheel cylinder would make a slight hum when I backed up after I did my brakes and found out the steel brake line was full of gunk so I replaced the steel lines as well ,it will throw you through the windshield now but every couple of months the small hole will squirt to the side when you take the cap off and the pedal is hard and after I clean it out it makes a vertical fountain when you barely push down on the pedal with your hand I am going to take it off and drill it out maybe this evening ,then I'm going to tackle the lip seals in my air pack to stop the fluid loss through the slobber tube I'm thinking about putting an O ring inside the lip to strengthen the actual lip so it will have more force against the bore ,anyone done this to theirs I need your thoughts please ,I have the short airpack.thank you guy's

I would not touch the master cylinder yet. I believe you have a problem with the linkage or airpack. Do you have dual airpacks ? Check the linkage going to the master cylinder. If your brakes are not fully adjusted the "throw" of the linkage can be too much. Sometimes this can cause the linkage rod to fall-out of the center of the master cylinder and catch the side of the master cylinder bore.
I would check all this before modifing anything in the master cylinder. Like I said before, if it worked fine previously then something else is causing the problem. Not the hole size of the compensation hole.
Now about the "slobber" tube leaking. You probably do need to rebuild your airpack or airpacks.
This should have been done with your brake rebuild. There is a member here that sells the rebuild kit for the short style airpack. I've forgotten his name but it ends with "Monkey:. Like "Army Monkey" or something like that. Sorry but my mind is not what it was remembering names anymore. I can remember how to rebuild a Allison MT42 transmission from back in the 70's, but I forget what I've eaten for breakfast !

 

[7-ton Rolex]

I would not touch the master cylinder yet. I believe you have a problem with the linkage or airpack. Do you have dual airpacks ? Check the linkage going to the master cylinder. If your brakes are not fully adjusted the "throw" of the linkage can be too much. Sometimes this can cause the linkage rod to fall-out of the center of the master cylinder and catch the side of the master cylinder bore.
I would check all this before modifing anything in the master cylinder. Like I said before, if it worked fine previously then something else is causing the problem. Not the hole size of the compensation hole.
Now about the "slobber" tube leaking. You probably do need to rebuild your airpack or airpacks.
This should have been done with your brake rebuild. There is a member here that sells the rebuild kit for the short style airpack. I've forgotten his name but it ends with "Monkey:. Like "Army Monkey" or something like that. Sorry but my mind is not what it was remembering names anymore. I can remember how to rebuild a Allison MT42 transmission from back in the 70's, but I forget what I've eaten for breakfast !

lol don't feel bad I am 57 and somehow have developed insomnia it's not to bad until I wake up my wife with the air compressor or start grinding steel and then there's trouble my truck is a 71 m35a2 it has one airpack and is the short style and it was rebuilt by me and it was before I joined SS I looked on this site and found the info needed to rebuild it ,when I took it apart it was clean and the parts looked new but I went ahead and rebuilt it anyway, now the lip seals were the problem and still are ,when I took it apart the fluid side was the same direction as the air side and I thought thats it !! because the exploded view showed the lips going in opposite directions or away from each other but it still works it's way through the tube after I rebuilt it ,like I said it has great brakes and I added a remote reservoir to it and mounted it on the firewall so I can keep an eye on it .thank you and the others for the knowledge and help.