Hello, 

 

     First time posting. I have looked around quite extensively but have not been able to pinpoint a similar topic. I have a 1985 GL wagon that runs great. Everything was working great until two days ago. I had not driven it for a week and a half because I was out of town. The temperature hear in Colorado was below 20 and as low as -10 for most of this time. Now once it gets warmed up to operating temp the heater does not work. The hoses going into the heater core are not particularly warm and when I squeeze them there doesn't seem to be anything in them. It will also start to over heat but then go back to normal temp occasionally. I checked coolant level and filled to maximum. Has anyone else experienced this or have any insight? I plan on getting a block heater soon but have a feeling that won't change much except for ease of starting. Any help is appreciated. Thanks, Noah.

Sounds like low coolant. Check the coolant when the car is warm and the heat is cold. The thermostat must be open to allow you to fill the coolant completely and burp out the air bubbles. Try filling the block by the upper radiator hose. 

 

Also, observe if there are bubbles coming out of the radiator or overflow tank while running, as this could be a sigh nof failing head gaskets where exhaust gas is pushed into the radiator forcing coolant out of the overflow.

I was able to get more coolant in that way. Thanks! No bubble thankfully! It also starts really rough in the cold. Besides a block heater, any suggestions that would help starting on those -10 degree days?

What weight of oil is in it right now? You should run 5W30 when it's going to be consistently below freezing for a good while.

Now that the coolant is full, be on the lookout for leaks. Perhaps you had a leak that leaked out enough to stop, causing low coolant. One thing to suspect is the skinny hose between the thermostat and the top of the block. Just a suggestion, it is as likely as is not likely. 

I am planning on changing the oil tomorrow. Running 10W-30 right now will make the change though. I will check around for leaks. Thanks guys.

Good luck on that oil change; isn't your high in Colorado for tomorrow a single digit number? 

Yessir, haha just finished changing it actually. Did the diffs while I was at it. Fingers are hurting a little bit. 0 degrees in Fort Collins.