We have a 2006 H3 with 120K miles. After replacing the water pump, it now overheats (redlines). The coolant boils. We've replaced the thermostat (twice!), the fan clutch, cleaned and flushed the radiator. Fresh coolant (red) and the problem continues. Our mechanic is out of ideas. The other little clue is that it cools down quickly with the heat turned on full blast, which is not fun since we live in Honduras. Ideas?

 

Sounds like you have a blockage in the water jacket. If it started after water pump replacement I’d start there.

 

A water pump is a man made part, man is far from perfect. Even brand new parts can be defective.

As BruceS said, I would start with the new water pump. If it is new, you should have a part warranty and could exchange it for a replacement. While the water pump is off, I'd suggest the mechanic look for any blockage to the engine block coolant passages and/or flush the engine block.

 

I will be doing some light trail driving tomorrow with an OBD-II reader to monitor the temperatures while driving. I plan on cleaning off the radiator as the video describes above this weekend and doing the test again in similar conditions.
It’s unlikely to change much, but why not try a cheap and potentially efficient fix. Thanks for the tip and link the the video. If I end up draining the system again I will definitely test the sensor.
Thanks again all!

 

I realize you are new to the scene. We frown on digging up OLD Threads, this one has already died its long ago life. READ: Old Threads/'Necro-Bumping'