Crazy Engine Temps and no heat

[Metroplex]

I was driving on the highway at -20C for an hour, and half way through my trip I lost all cabin heat and my engine temp swung continuously from extreme heat to extreme cold. -20C and no heat is awful. Any thoughts or help would be great. Thanks.

 

[Bob Ayers]

Check your coolant level...

 

[Jspafford]

Stuck thermostat?

 

[MAKG]

Regardless of the problem (both issues above are plausible, though I tend to suspect Bob is right and you have a leak somewhere), you NOW may have a cracked head or two. Time for a leakdown test and a cooling system pressure test.

 

[Metroplex]

Coolant level is healthy