DEF filler cap stuck? won't budge

[eternam]

Thanks again everybody. I was finally able to get the cap for the active tank off. It was on there extremely tight. The tech or whoever owned the vehicle before screwed it on waaaaay too tight. I had to use a piece of rubber and warm up the engine for a while to get it to budge. The passive one came off without a problem.

[Ozer]

Good to hear. Since we are on this topic, how much do you guys fill the tanks? Allowed amount or till the lines are full and no more fluid can be put in?

I filled mine all the way till no more can be put in and after 2 weeks i started getting the DEF temp sensor issues, wondering if i overfilled or if its just a coincidence

[Doug Huffman]

What indicates the allowed amount?

I know that on my recent dealer's service department fill, both tanks were pressure filled until the excess squirted all over the engine compartment. Then the deleted let me, the customer, see the mess.

I intend that I be the only one to refill my DEF and that never again is a nozzle-hose-pump-tank head rig used. I suspect that the impulse pressure - water hammer - is damaging the plastic tanks.