I have a 2007 C4500 2WD with a Chariot Hauler bed installed in Elkhart Indiana, truck has 5000K miles on it. Recently, last two fill ups, the transfer tank (98 gal) is leaking fuel which is splashing/spraying up on the rear window and on the bed. Problem seems to occur when the tank is full, and does not seem to be related to running the transfer pump. A quick look at the connections didn't reveal anything obvious to cause this issue. Any on had the same type of problem? Thanks.

Mine leaks when it is really full and the heat expands the fuel.
The cap on mine is also supposed to be vented but when you take it off to refill it you had better turn your head cause there is alot of pressure coming out of it.
Hope that helps.

I would replace the cap.

I would replace the cap.
i would start there, but the fuel does expand. dont fill to the very top

i would start there, but the fuel does expand. dont fill to the very top

Wiser words never spoken.

The problem, it seems is a faulty weld on the top of the tank, which has cracked. Leaks like a sieve. However, chariot conversions have been great, a new tank is on it's way.

I had a tank from weather guard that did that once. Had to fill it up with water before I welded it. No air space no explosion!

I tried to buy a new cap for mine but could not get one unless I bought the whole neck assembly.
Oh well we built it ourselves using the title 49 specs and I have all the paper work put together to back it including pressure testing.
Cap still leaks though.
Specs for DOT are (can't remember the mils) but 3-4 drops a minute?
I figured no leaks but in the title 49 stuff is states the amount of leakage allowed.