I started my truck today and let it run for about 5-10 minutes because it is 10 below zero today. On the way home my temperature gauge read around 190-200 and I noticed that everytime I let off the throttle from 45mph the temperature gauge would drop to about 140. Is this normal? If not what is wrong with it. It's a 2003 chevy silverado 1500.

  • Normal operating temp is about 195 degrees. Is the coolant overflow/expansion tank at the normal level? And is it clean or muddy looking? – mikes Jan 9 '15 at 4:47
  • I meant it stays around 200 and drops to around 140ish.the coolent is low. The message just came acrossed my driver information screen.the coolent looks normal to me. It's red in color. – bobby Jan 9 '15 at 6:10
  • @bobby ... could you please edit your question with the correct numbers then? It is very confusing as it is. The question implies a huge issue, while your comment not so much of an issue. Please help us to understand so we can give you the correct answer. – Pᴀᴜʟsᴛᴇʀ2 Jan 9 '15 at 12:09

My first thought is a defective thermostat. If by low, you mean the over flow tank is near empty you need to bring it at least close to the normal level. Recheck it over several days. The other possibility is an air pocket. When the air pocket settles in the area of the temp sensor the gauge drops. This is due to air being a poor conductor of heat. This is more likely if the overflow tank emptied due to a small leak that went unnoticed.

  • Does that also mean that the heat will inermittintaly blow out cool air as well? – bobby Jan 10 '15 at 4:27

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