2006 Chevy Colorado Overheating

I have a 2006 Chevy Colorado, 5 cylinder, automatic, 4wheel drive with 62,700mi. 1st problem occurred in 2013 new thermostat was replaced then in 2015 temp. gage shows overheating problem again. All diagnostic problems have been analyzed by mechanic and nothing further could be done. Mechanic suggests to take truck to dealer. The temp. reading still shows above normal operation and the engine compartment has signs of overheating also. If the truck driven on uphill range the temp. goes higher I refuse to drive in this condition which will surely ruin the entire engine. Need your helpful advice to determine what is wrong. Thank you

Hmm. A “mechanic” who can’t figure out an overheating problem. Is there a big tree in his backyard? Most common problem with these overheating is the fan clutch.

You are correct to be concerned about driving the truck with an overheating problem present. First off, if it starts to overheat, slow down and see if you can cool it off a bit by turning on the passenger compartment heater to max. Not a fun thing to do this time of the year, but folks have saved their engines by doing this.

Next you want to be sure it is actually overheating. Suggest to buy one of those laser-IR thermometers, the kind where you shine a light where you want to measure. Then compare the reading you get on the top radiator hose compared with the dash gauge. Maybe you just got a flaky sending unit is all for the gauge.

If you determine you actually have an overheating problem – and if the car was working correctly you wouldn’t, so there is some kind of problem here – here’s the likely causes:

  • Radiator cap defunct
  • Air bubble in cooling system
  • Low coolant
  • Wrong water/coolant mixture
  • Radiator cooling fan not spinning fast enough, or not spinning, bad flan clutch
  • The transmission is overheating for some reason
  • Ignition timing too retarded – check at several rpms at least to 3K, not just at idle.
  • Radiator is clogged, or fins are bent blocking air flow
  • Compromised head gasket
  • Thermostat problem
  • Water pump problem
  • Coolant passageway(s) are gunked up
  • Rubber coolant hose(s) are collapsing

If I had this problem w/my Corolla, what’s the first thing I’d do? hmm … well, I’d see what the laser temp meter showed at various points in the cooling system, including the two hoses that go through the fire wall for the passenger compartment heater. If nothing unusual showed up, I’d remove the top radiator hose and run the engine from cold, at idle, and see if the thermostat was fully opening. When that happens, lots of water will start pouring out of that hose. Not just a little bit, it should be like you turned the garden hose on full force. And that water should be very hot.