Years ago, I went to a salvage yard and bought a used fuel tank off a junk truck, put it on one of the semi's and have been using it for a hydraulic tank for my wet kit, well after all these years today for some reason, the cap ended up missing, probably on some of the roughtest roads I've ever been on today, but then it dawned on me, if I recall it was off a foreign truck of some sort at the time. Well none I have around here fit it, it screws on like a smaller international or freightliner tank does but now I need a replacement cap. The first thing my local store asked was what trucks it off of and when I told them I couldn't remember things went down hill pretty quickly, after I told them probably foreign it ended even quicker. It didn't sound too promising as to getting a replacement cap from them. Is there any place one could get a replacement cap that screws on and might be a strange thread size or how to even measure the thread size to know what to even be looking for at all, I"ll admit all these years I've never lost a fuel tank cap before or ever needed one for that matter but I guess there's a first for everything. Any ideas would be appreciated, thanks in advance.
Perhaps a machine shop could measure the threads on the tank opening and make a cap with aluminum tubing or billet. If you did that have two of them made. That is almost a guarantee you won't ever lose it again.
In the mean time, an expanding rubber plug will probably buy you some time to find the right one: https://www.google.com/search?rlz=1...663.8j1.9.0...0.0.0..1c.1.17.serp.a7LVEbuBLDo
The threads on a lot of the tanks are like (or actually are) pipe threads. I just ordered a cap for an IH that is listed as a 2" but measures 2 5\16". I ordered a Velvac brand and their catalog descriptions show both nominal and actual measurement along with thread pitch. I ordered one from Ebay vendor yesterday because my supplier would have taken an extra week. Amazon.com shows a large number of caps also. Edit: Velvac also shows a couple of adapters to put a standard cap on some odd thread.
Every tap and die kit has a thread pitch gage. Just match up the threads on the gage to your tank and now you know the thread pitch. (May be metric if your tank is foreign) Now measure the outside diameter with a set of calipers and a machine shop or anyone good with a metal lathe should be able to make one up for you.
depending on how much pressure the tank will build up. I had a power up/down hydro tank system for my roll off and only used a valve cover breather cap. Only if it was overfilled with fluid would it come out from the cap. Most auto parts stores sell them. It's based on the id not the od so there is a little room to play with. Also have used a plumbers cap that you tighten up with a screw driver.
Thanks for the idea's, at least now I have options to work with, I've been so busy I haven't had time to worry about that truck, for a temporary fix while it sits on the jobsite in the rain, we took a plastic cap off of a 2.5 gallon jug and taped it on, at least it keeps the rain out while I figure out how to do it right.
Have you looked this tank over real close to see if there are any numbers on it? Many fuel tanks have a tag giving the capacity and often a part number. This could get you headed in the right direction. One more idea how about posting a picture maybe some one will recognize it!