Idle Heat Fine until 30-40mph..then cold

Mbietsch

New member
Jan 30, 2022
2
1
1973 Chevy K10 Step Side. I'm having issues with the heat. I know I have a small Coolant leak somewhere, but not sure where at this point. My issue is the heat in the truck works fine when at idle. As I increase speed to around 30-40mph the heat turns to cold...and I mean cold. Like the temperature of the outside temp. I would think if it was a heater core problem I would have the problem all the time. Anyone else had this problem? The system is full of coolant. Thanks!
 
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79c30parris

New member
Jan 30, 2022
1
1
Yeah it's installed and operating properly.Check you coolant level if it’s low the coolant will not circulate through the heater core also try letting it idle on an incline to see if there is an air pocket in the coolant system. An if you have a leak it will most likely present its self again until it’s fixed