Well it happen again. Got cold here in Missouri and my brake fluid drained out of the master cylinder. I am going ahead to mount the master cylinder on the firewall. A friend gave me a power booster and master cylinder for disc brakes. I was wondering if it can be hooked up to drum brakes front and rear. I do not have the funds to put disc on the front. I do not want to have to put extra holes in the fire wall to mount just a master cylinder then have to put the holes to mount the booster.

 

Are you saying the fluid drains out of your master cyl. in the original location when it gets cold?

 

Obviously, you have a bad master cylinder. They don't all leak out when it gets cold. Replacing it with a new one will be the cheapest and easiest thing to do. And no, you can't use a disc brake master with drum brakes (unless you add a 15lb check valve on each of the front brake lines).
Chuck

 

Yes when it gets cold the fluid leaks out. I have not been able to see where it is leaking though. Last year when it did this I just filled it back up and bled the brakes. They were find all summer.

 

I have a 46 Merc with the same brake Master Cyl. the ford trucks use. In 3 years and 9,000 miles have not added a drop. So cold is not a issue. It is in a unheated shop and I drive it off and on all winter.
It has to be a leak someplace, connected perhaps with the change in temperature, causing something to shrink in the system..If there is a leak it has to show up someplace. I am betting a wheel cyl or line connection bleeding over time since your not driving it as much, if at all in the colder weather.
I have a underfloor M/C on my 55 and even tho it is newer it doesn't leak a drop and doesn't have check valves. I have disk/drum configuration.
So out of the two vehicles I drive with underfloor M/C no issues with leaks on either one. I am also in Missouri and both are in a unheated shop.
Good luck finding your leak.
Larry

 

The stock masters at napa are reasonable.

 

Has to be something with the cold weather because I checked it on a regular basis all summer long and did not have to add any. I am putting the master cylinder on the firewall because eventually I want power disc brakes. The under the floor setup pushes the master cylinder back and you no longer can check it through the stock observation hole in the floor board. Plus I feel it will be easier to set everything up(ie porportioning valve, etc).

 

It is not uncommon for older farm trucks to set through the winter and the wheel cyls leak. In warm weather or when using them somewhat often no problem. New wheel cylinders or rebuilding them eliminates the problem.
I think what happens is the rubber cups get hard with age and more so when cold and don't seal well.
A new master cyl or a rebuild if the cylinder bore is smooth should solve your problem.

edit
If you plan to do power later anyway and want things not under the floor I understand that.