Forum Discussion

maillemaker's avatar
maillemaker
Explorer
Jun 11, 2018

Can anyone tell me what this coolant line is for?

I have a 1990 Winnebago Warrior RV built on a Ford E350 van. There are, of course, two bypass lines that come off of the water pump and manifold. Normally, these would route to the heater core. O...
jplante4's avatar
jplante4
Explorer II
Jun 11, 2018
Looks like a bypass for when the heater valve is shut. If the heater is fed directly off the water pump, when the thermostat is closed and the heater valve is closed, there's no flow through the pump, causing it to cavitate and heat up.

Just a guess.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,344 PostsLatest Activity: Dec 26, 2025