Cadillac Repair: Heater Not Working in 1993 Cadillac Sedan DeVille, coolant level, coolant systems

Question
The heater in our 1993 Cadillac Sedan DeVille has stopped working (air flows properly but no heat).  Upon checking the coolant level, we found that it was down significantly (approx. 3 quarts).  Since then we have filled the car with coolant, including the resevoir, but still no heat.  1. Can the operation of the system without proper coolant level cause a lingering lack of heat even after the coolant level is restored?  2. Is there a "reset" option available to restore the heater function once the coolant is replenished?  3. Can you offer any guidance on troubleshoot and/or repairing this in general?  Seems quite coincidental that the heater stopped working and the coolant level was down substantially.  Thank you for your help in advance.

Answer
Hello,

For years coolant systems in vehicles have been a closed system. If you are down on coolant, heating problems will occur. I would be very concerned as to engine damage because Northstars do not react well over heating. I would be concerned as to where 3 quarts of coolant went--very concerned!!

I would suggest figuring out where the coolant has gone. To do this, go to a service center that has a pressure tester. I have one in my garage. The radiator is filled to the top and the pressure tester is pumped to 15 pounds. Then wait to see where the coolant is leaking from. These northstars are known for leaking intake manifolds and bad head gaskets.

You need to find the leak first. As far as the heat, its very possible that you may have a air bubble or a bad heater control valve in the engine.

Get the engine looked at first!

Rob