A week ago I was driving on the interstate and my truck all the sudden went into limp mode so I pulled over to find out that the water pump was leaking coolant and that all the coolant was somehow forced into my overflow tank(more so than usual, about 3/4 full when it usually is barely 1/4 full). So I drained the radiator, replaced the water pump, filled it back up with dexcool and took it out and right when I got back to my apartment it started making a funny noise in park(kinda like it did when it overheated a week ago), so I popped the hood to find the coolant again all in the overflow tank. Coolant is not leaking out anywhere either.

I sat there for about 5 minutes to see if it did anything with the truck off and eventually all the coolant in the overflow tank started to go back into the radiator and I could hear and feel coolant going through the upper radiator hose.


I've never heard or seen of this happening and was hoping some of y'all could help me out. I was thinking it might could be a bad thermostat, but I really have no idea.

Any help would be greatly appreciated

 

It could just be air locked from after you changing out the water pump.. Always a good idea to change thermostat when changing water pump.. I change a water pump & stat on a 5.3 & it took for ever to get the air out & to get the stat to open..

Is the heater inside working normal?

 

When I blew a head gasket the compression in that cylinder leaked into the coolant passage and pressurized the cooling system driving coolant into the reservoir. Maybe you have a bad head gasket or a cracked head. Check your compression. Hope it is something else.

Check for proper circulation and potential air lock first of course.

 

If the engine were overheating the coolant would first go to the overflow as it expands, filling the overflow, then it would go out of the overflow hose and on to the ground. If you had an air pocket after changing the water pump, this could be the case.