Leaking water pump replaced. Now no heat and overheating?


Asked by Mar 28, 2015 at 07:10 PM about the 2004 Chevrolet Express

Question type: Maintenance & Repair

My 2004 Chevy express 3500 box truck was leaking water out of what appeared to be
the water pump. I purchased a new pump and thermostat. After replacing the pump and
filling the radiator I started engine to come up to temp. Never seemed like stat opened,
water level only went down slowly. After engine temp started climbing over normal I
turned on heater and no heat at all, just cold air.  With engine climbing above operating
temp I was thinking new stat is no good but with no heat I'm wondering if something

3 Answers


Just by taking a wild stab at it, I would guess that you have a TON of air in the system. If there is enough air in the system, it basically becomes vapor locked, especially in the newer engines. Best way maybe to remedy this would be to take the thermostat back out, fill the block VERY slowly with antifreeze where the stat goes until its full, put the top radiator hose back on the stat housing, then fill the hose just enough that you wont spill it everywhere when hooking it bck up to the radiator, then fill the radiator VERY slowly also. That should do the trick. They also make thermostats that are guaranteed not to stick closed if your worried about that. Hope this helps

3 of 3 people found this helpful.

Thank you. That makes sense. I will give that a try.

1 of 1 people found this helpful.

What TY said is correct . I experienced same problem. I took the hoses off. Filled as much as I can slowly with coolant . Started the van. Let idle with few revs all is good

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