The Stovebolt Site Forums The Shop Area Interiors Brake Master Cylinder Access

I insulated the floor of my ‘54 3100 today. (It should be noted that my truck has a replacement repro floor.)
I wondered how to deal with the brake cylinder access.
Given the fact that the access hold is only about 2” in diameter I really don’t think I can remove and replace the cylinder top and retaining clip through it, so I’m thinking I’m going to have to perform that maintenance from underneath the truck.

Is my 2” access hole typical of the original? Do you 3100 guys usually work through the floor, or is it pretty common to go underneath?

I sure wish that master cylinder was on the firewall!

You can't add fluid from underneath.

The hole should be 3" in diameter, which is large enough to put a socket wrench on the cover and remove it.

Socket wrench? My master has the common retainer clip over the top.

Did someone replace it it with a dual reservoir unit?

Here's mine and its location under the floor.

Affirmative.

I'm surprised that whoever made the swap didn't relocate it to the firewall.

I don't know how it would be possible to check the fluid level or add fluid from under the truck, though.

Guess I’m going to find out if it’s possible. There is some clearance between the floor and the cylinder top.
I’m also going to look into that relocation.

There's no way you'll be able to look down into the reservoir from under the truck unless they lowered it.

You'll probably need to add fluid through the hole in the floor with a turkey baster.

It is not a big deal to increase the size of the hole in the floor or make a new one, when I switched to a split master last year on my 46 I had to make a new hole 4” further back from the original, just cut a hole 1/2” smaller than you want, take a hammer and work around the hole gently tapping the edge over to create a 1/4” flange at 90 degrees, I used a SS plate with center screw from plumbing supply (clean out wall cover) to seal it.
I could have made hole same as orig and used another orig plug but I wanted big enough for my hand to fit᠁
In the pic u can see the hole and the cover next to it.
Electricians have knock out seals in various sizes, plumbers have stainless clean out wall access covers᠁..to each trade his own᠁᠁

Chuck

Nice work Hank(s) ,
What tool did you use to cut that hole?
I wish I had had the foresight to perform that modification during the main project.

How about installing a reservoir under the hood and modifying the MC cap to connect a hose between the two. That way you fill and monitor the level from up above

I cut the hole with a (wait for it) hole saw, since I’m a retired boiler/ plbg contractor I have big sizes sitting around.

Chuck

You can go the hanging pedal route. There are plenty of companies making kits. You can go with a remote reservoir kit. You can also, with some difficulty, service the master from underneath with a turkey baster style tool that has a hole attached. You will have to use a mirror or your fingers to feel how high the level is. Probably why I went with a see through reservoir bowl on my Model A.

On my first truck, I found a weld in/bolt in flappy door that stayed under my rug. You can get them with lock cylinders if you're feeling fancy. McMaster Carr has those things listed in their catalog. I believe under "access door." Get it as big or as small as you want.

Do you have a right hand drive truck? That is the only way I can make sense of that picture...

LOL, I thought the same thing at first, then I saw the steering wheel and column at the bottom of the pic. It's taken from inside. Also there's the hanging pedal.
So the master cylinder is under the dash - real easy to get to.
Inspection mirror?

What’s a hanging pedal?

Pedal hangs from a bar under the dash instead of going through a hole in the floor.

That picture is an example, from my Model A roadster, of a plastic reservoir so you can see the level at a glance. There is no rule book that says you have to use an integrated metal bowl master. That type of master would work under the floor of a truck, inside the firewall of a truck, or on the firewall in the engine compartment. It just so happens I wanted a clean firewall on my Roadster, so the assembly went inside my cowl. Everything is a tight fit, but doable. If anyone wishes, I have 2-3 examples around here of a remote reservoir, master cylinder systems.

My '51 has a hanging pedal system with a master in the engine compartment.

I've done the OEM master location before and I'm no longer a fan of it.

The picture is now pretty clear.
For background, my project was originally planned to span 1 winter, that of 2020/2021. As usually happens, mission creep set in ; the project grew like The Blob in the old Steve McQueen movie. As the project ground into early 2022 it was decided that my truck would be on the scene of my daughter’s June wedding as the “getaway car”. Seemed like there was plenty of time᠁. Things happened quickly after that. I remember selecting the reproduction ,original pedal looking dual cylinder brake assembly, never giving a thought about maintenance. I first drove the truck last October (it was static display at the country wedding) , haven’t given hard consideration to that access until I insulated the floor a couple days ago. So here we are.

If I had to do it over again I’d probably go hanging pedal w/ the rest of the gear in the engine compartment. At this point I’m not inclined to tear out the new cylinder that is in the original location and functioning well. I think I can pop the retainers from beneath the truck , check and fill from the top , (turkey baster) , then go back below to reset the clips. Not an attractive prospect. I clearly need to cut a larger access port. Boats have lots of those ; there are near-flush press fit covers for those , like the one in the deck of my powerboat that gives me access to the fuel tank sending unit.

Man oh man , it would have been easier to address this at the proper time. This is what I get for
a) being in a hurry
b) thinking it would be cool to have the old style pedal in my heavily modified truck.
Live and learn.

Thanks again to this crew for giving yet another crash course. I guess a project of this nature is never really done.

I like a clean firewall. I cut a bigger hole for access on my dual master cylinder for 52 panel. In 7 years I think I checked it once. I never regretted leaving it under the floorboard. I think you'll like it in the long run.

Clean firewall᠁
I did move my battery, but at least that is a tidy geometric box. I agree that I do not want any more gear in there.

Part of the joy of owning such a vehicle is it’s simplicity.

Alvin has it. Unless you have an issue, leaks in the system, putting tons of brake usage on your brakes, you really only need to check the master on your regularly scheduled PM and will probably need to top it off rarely. Usually, that'll be the time that you fund out you misplaced the turkey baster filling tool.

Agreed.
Existing mechanisms will remain in place. They ain’t broke so I won’t fix ‘em.

My setup is very stock under the floor with access via the 3" hole under the rubber floor mat. It has been 2-3 years since I've checked my fluid level. This thread is a good reminder.