I’m freezing on my morning commute

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Joined: Thu Nov 12, 2020 9:47 pm

I’m freezing on my morning commute

Unread post by WBH » Thu Nov 12, 2020 10:08 pm

I have a 2003 K2500 Duramax that barely gets warm in the winter. You have to drive this truck about an hour before it will get warm enough to be comfortable. I have had this truck for about 10 years and it has been this way since I bought it. The engine temperature rises to about 165, but rarely gets warmer.

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Location: Oregon

Re: I’m freezing on my morning commute

Unread post by carriedi » Sat Nov 14, 2020 2:12 am

Engine temp at 165F is a little low but it should be hot enough to be able to transfer heat through the heater core. With the engine at it's normal running temperature, check the two coolant hoses that go through the firewall for the heater. Are they both hot? One hot and one not? If you have anything except "both hot" then the heater core my be plugged or partially plugged up. If both hoses are hot then the blend door in the heater system may be messed up.

I use a thermal imager to look at the two heater hoses to tell me what they are showing as far as heat goes. If I see one hose hot (that would be the engine side) and the other side cold or a lot colder (that would be the return side) I hook up a cooling system flush machine to back-flush the heater core. I usually hook up to just the heater core and back-flush for half an hour. Afterwards the heater core will usually work again. Put the heat on hot. Blow through the vents. close off the side vents if you can so the air comes out the middle vents. Put the fan on low. You should get heat at 135F or higher.

thermostat specs say the the thermostat should start to open at 188f and should be full open at 206f. Any where between is good. So even if the running temp is around 185F that should be okay. 165 is a little low but without using a scanner to get a digital read out the gauge may be off a little. You could replace the thermostats to see if that raises the base heat temperature. But, even 165F should be enough to get heat from the heater core. So, check the coolant hoses to the heater core.

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