Master Cylinder Issue

[fkowalski1942]

All,
I´m having a strange issue on my M35 brake system... i dont know if my problem is the Airpack or the MC...

My question is, the vent hole inside the MC aparently are drilled, and comparing from pics here on Steel Soldiers this hole is 0.02" only... is there any problem if this hole is bigger? I seems to be a 2mm hole +/-...

Best Regards
Felipe

 

[frank8003]

Is this M35 2C?

 

[dmetalmiki]

There would be a vent pipe coming out there so if it is missing there would be a larger threaded hole. I have my secondary 'top up' cylinder from the cab going into mine.

 

[fkowalski1942]

Heres a picture of my MC

 

[fkowalski1942]

 

[fkowalski1942]

Here is a picture of a MC that i found here on Steel Soldiers, note the difference from the size of the vent hole

 

[fkowalski1942]

Also, the rubber cup aparently is blocking about 75% of the hole... is this correct?

 

[rustystud]

You have other problems besides the vent hole. You have some major rust issues ! There should not be any rust in the master cylinder. Your bores could be rusted also, so you need to take this unit apart and see what is going on here.

 

[frank8003]

maybe this will lead to a fix?
One should replace that MC

Did you removed the splash plate from the underside of the MC cap as suggested in the Ross write-up?


The vent tube port of the master cylinder fill plug is
threaded for 1/8-inch NPT. Below the vent port is a
splash plate that prevents fluid from splashing up into
the vent tube. This must be removed for the new fluid
reservoir system to operate properly. Use a punch to
knock it out.
• Install the 90° elbow into the 1/8-inch NPT port of the
fill plug.
• Reinstall the fill port plug into the master cylinder.
The vent tube port of the master cylinder fill plug is
threaded for 1/8-inch NPT.

From http://www.roscommonequipmentcenter.com/page34.html
Easy Access Brake Fluid Reservoir for Military 6x6’s
Roscommon Equipment Center
National Association of State Foresters
in Cooperation with
Michigan’s Forest Fire Experiment Station see newsnote #17

 

[jbayer]

So, the OP is calling this a vent hole, but it appears to be in the bottom of the MC, looking in through the cap opening. Looks like the fluid ports to me, supply and return from the the piston.

 

[Recovry4x4]

That is a compensating port. It allows fluid to re-enter the reservoir after release of the brakes.Either way, your master cylinder requires servicing, rebuilt or replaced. Brake components are critical on a deuce, do it absolutely right.

 

[fkowalski1942]

I decided to replace the master cylinder, theres a lot rust inside it and probably inside of all other components of the brake system too, time to check everything.... Im just curious about the larger hole of the compensating port, why 0.02" hole on the first type and 1,5mm hole on the second

 

[Ratchetop]

I will check that and let you know what I find.
Thank you

 

[Big Al UK]

Hi

I am replacing the Brake Master cylinder on my M35 a2 1958 any tips and advice how, what to do or not to do, it is very rusty on the outside been spraying the bolts with wd 40 to help worried about the pipe breaking when trying to undo it. I have a new unit to drop in.

Al

 

[fkowalski1942]

Theres four 9/16" bolts on the body of the master cylinder, one of these gives a headache to remove....
To remove the pipe use a 1/2" wrench and be careful avoiding strip the hex nut... to install this nut again first thread with your fingers and use the wrench just for the final torque.
I hope you can understand my bad english...

I will be 150 miles from you in January, let me know if you need anything. i have some spare brake lines and brake pipe nuts around.
Regards

 

[Big Al UK]

Theres four 9/16" bolts on the body of the master cylinder, one of these gives a headache to remove....
To remove the pipe use a 1/2" wrench and be careful avoiding strip the hex nut... to install this nut again first thread with your fingers and use the wrench just for the final torque.
I hope you can understand my bad english...

I will be 150 miles from you in January, let me know if you need anything. i have some spare brake lines and brake pipe nuts around.
Regards

Thank you will be in touch if I need any thing looking to do it over the next few weeks I hope but work is getting in the way !