Diesel heater tank cap not tightening

A few weeks ago, I stuck my head into the hatch at the front of our camper trailer, and noticed there was a fair bit of diesel spilt on the plywood, from our diesel heater tank. I wasn’t entirely surprised with the tracks we’d been on, and the silly shaped tank, but put my hand in anyway, just to check the lid was tight.

It wasn’t, and I gave it a nip up, only to feel it get completely loose, and then it wouldn’t tighten at all. Ugh!

I undid the strap holding the tank in, and slid it out, carefully removing the cap, and lifting it up. To my surprise, a small amount of blue coloured diesel tipped out, and quickly diluted into the tank. Puzzled, I sat there wondering what on earth had just happened.

I quickly realised that the diesel must have reacted with the plastics (no doubt the cheapest material possible used in our Chinese Diesel heater), and was causing it to not tighten up. I played with it some more, and worked out that if I removed the internal cap and one way valve, the lid would work.

Diesel heater tank cap
Our diesel heater cap lost the ability to tighten up

I had a few options then; let it leak, remove the one way valve (and it would leak for sure), or try and modify it. I chose the last option, and trimmed the internal section down to a point where it wasn’t holding the cap up anymore, and it tightened up.

A few weeks later though, I opened the hatch again, and saw the diesel level down a bit lower, and we’d not used the heater since. Apprehensively, I reached in and found the lid loose again, and this time it was doing it even without the centre piece removed.

I’ve heard of this happening before, and suspect we’ll end up getting a different tank, but tried thread tape first (which didn’t work), and then I got some of the chux dish washing cloth cut to size, wrapped around the thread and tightened up, which seemed to hold. I threw a cable tie on for good measure (just in case it came loose), and called it a day.

I’ll try and find another cap, but we probably need to get a different tank!

EDIT – this is still going strong a year later, with a cable tie on it. The blue lid is clearly not suitable for diesel, and its gotten even looser, but so far its not a major problem. We’ll replace it with something else when we our big lap of Australia finishes.

Diesel heater diesel tank
These diesel heater tanks often have issues with the lids

Apparently though, this is a really common option, and after the time I spent mounting this tank I feel a bit annoyed. Fortunately, the tank is mounted in a non sealed hatch at the front of the camper and a small amount of diesel spilling really doesn’t matter much at all.

We really loved (and realistically, needed) our diesel heater in the Victorian High Country, and wouldn’t go around Australia with kids without one, and so the tank needs replacing and life will go on.

Have you had this happen to you?

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