Hi, ok, so here is what happened. I forgot to close the cap of the hole where you fill the motor oil and drove the bus for 60 miles before realising this. Could that have caused the tube to melt?
Yes the tube was plastic, hard plastic.
The engine is a Cummins 8.3l rear engine in a Thomas mvp bus. He motor still turns on when I turn on the ignition. I haven't driven it yet, because I don't know if the oil level is good.
Thanks for your replies so far.