2001 chevy s10 2.2 will not reach normal operating temp. First noticed when defroster was blowing cold. Replaced thermostat with Stant superstat with no change whatsoever. Coolant level is normal. Out of ideas, please help.

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    What does the temp gauge show? – Moab Apr 7 '18 at 21:06
  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Apr 7 '18 at 22:59

First Check the heater valve is working and opening to allow the hot coolant through.

Second check to see if the heater matrix (a small radiator) is blocked.

Either of these could be the cause or even a blocked pipe. It could also be a failing or failed water pump, but it should have shown signs of overheating...

I have assumed that the new thermostst is functioning correctly - perhaps testing it would be a good idea...

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  • the temperature gauge indicates midway between 100 and 210, approximately 160F. I am considering having the radiator shop flush out the dexcool and replacing it with the green stuff. I did not test the new stat. – balatro Apr 8 '18 at 0:47
  • What is the temperature specifications of the new thermostat? If too low, the whole cooling system may be held at a too-low temperature. – DavidSupportsMonica Oct 11 '19 at 14:38
  • @David “what are...” – Solar Mike Oct 11 '19 at 15:52
  • @SolarMike Is my comment unclear? Thermostats (at least in the old days...) used to come in several temperatures. Here, the OP would want to determine that a) the thermo has the right specs, and b) that it's opening at the right temperature, and not at a lower temperature than expected. – DavidSupportsMonica Oct 11 '19 at 16:14
  • @David what are the temperature specifications or what is the temperature specification... usually a range though and they are not very precise in my experience. Best electric fan control I ever had was when i used a cylinder stat (from a hot water tank) on the bottom hose... – Solar Mike Oct 11 '19 at 16:46

I noticed that you mentioned Dexcool in your comment to solar Mike's answer. There is a known issue with Dexcool turning to a kind of sludge or mud after many years of use in a cooling system. This could easily clogged up something like a radiator core. Just do a Google search for Dexcool sludge or Dexcool mud. You may want to check your cooling system to see if it needs to be flushed here is a good Guide to the subject :


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  • Could you quote the relevant parts of that article, in case it goes down, so we have the resource here still too? – Cullub Jun 14 '19 at 0:43

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