Your 5 ton, The spring brake tank and RUST - My M936

[Mullaney]

Well, in the grand scheme of things I can't say that it surprised me when I found a little spot of rust was the problem... I have had an ongoing battle with the stuff! I had a persistent air leak that sounded like it was under the drivers side step. There is a wad of air lines in the "box" in front of the air cleaner. With the truck running to build air - finding it was next to impossible. So, I attached shop air to the front left glad-hand.

Crawled under the truck and started poking around and found the source. Over the years, my 1984 model M936 had gathered dirt and road salt and general crud that laid on the metal plate (picture below) and it eventually ate through the metal on the air tank.

Thanks to simp5782 I have a replacement tank on the way! He also suggested using Prune Spray on the bottom of the new tank and the plate too. Should protect it and keep this from happening again.



Anybody looking for a new project - or something to do to your truck - this might be worth the effort. All it took was a 9/16 wrench and socket to pop off the plate under the step. A 3/8 socket removes the nuts on the u-Bolts on the tank and the plate will be on the ground. If yours looks like mine, some scraping, cleaning and painting might be a good investment in time.

 

[m715mike]

Wow, thanks for the post!

That’s not the first place I’d check for an air leak. Now I’ll have to look at my M936.

 

[Mullaney]

Wow, thanks for the post!

That’s not the first place I’d check for an air leak. Now I’ll have to look at my M936.

It wasn't for me either, but with the truck off and "shop air" plugged into the truck - it made finding the source a lot easier.

What surprised me was the design. A "metal tank" bolted down onto a "metal plate" with two U-Bolts. No rubber bumpers, no cushion at all. Obviously it was a pretty solid design because she was 35+ before the problem showed itself.

I think it is definitely worth a quick inspection for everybody. Fairly easy. It you see crud piled between the tank and the plate - you WILL eventually have the problem I have (had). That second image above has a screwdriver pointing to the problem area...

 

[Hamrick907]

I think I will take a look at mine as well.

 

[Crf450x]

That’s interesting. I went to look at mine and it is against 2 small vertical pieces on my m923, totally different setup.

 

[Mullaney]

That’s interesting. I went to look at mine and it is against 2 small vertical pieces on my m923, totally different setup.

Strange. I know that on the 40's vintage duces I have worked on, the mounting is a little different too. A lot of them have something that looks like a muffler clamp that the tank sits on.

All the same - finding that (factory mounting) tank on the horizontal metal plate - and rusted through was a somewhat scary thing to see.

 

[71DeuceAK]

Thanks for sharing! Sounds like a common issue.