My mechanic is stumped...heater problem and more...

My husband asked the same question because he suspected it might have been the computer module. I think the mechanic told him they had scanned it but it didn't show anything which I thought was kind of odd. Usually, when they scan it for the codes, it will give you some indication of where the problem originates from. I'll have to check with my husband and see if he ever got a definitive answer on that. I couldn't tell where it was leaking from...will have to wait for daylight to see if we can tell where it's coming from. You'd think if the coolant reservoir was leaking they would have noticed that when they replaced the reservoir cap.

Thanks to you both...very helpful and it makes perfect sense! I know just enough about the inner workings of an engine to make me dangerous and it can be overwhelming, but this was really helpful. Thanks again!

UPDATE...My husband just reminded me, because I forgot:) , that the thermostat has already been replaced too as well as the coolant reservoir...they noticed it was cracked so they replaced it and the reservoir cap. Also (Tom), back to your response...It was blowing cool air when I last brought it home from the shop...it was heating ok when I left the shop and by the time I got home, it was only blowing cool air...it ran fine, just no heat. Since the last visit it seems heat is working fine. Since it has been SO COLD here in VA, I let the truck warm up a good while before I drive it, but then after driving it for a few miles the temp gauge shows its overheating and the oil light and SES light comes on. Once I restarted it and headed for home, the heat was working just fine, just the SES light on but still losing coolant from somewhere. Considering that I forgot about the t-stat being replaced already, could it still be the water pump?

Main place to start is find the leak place. Loose hose, ect.

Low/no coolant level means no heat, takes coolant to have heat, its leaking out so no heat after it leaked out.

A lot of shops today are just parts changers, know little about how to diagnose issues. If their smart phone dos not detect the issue for them they have to replace parts until they stumble on to the failed part or issue. Your experiencing what many others do too, the on-board computer does not tell all, someone still has to know what to do with any information the computer may give, but in your case it does not tell you a thing so tell those workers at the shop to locate the leak first before going to the next part to replace. Get the owner of the shop out the warm chair in the office.

After all the over-heating I would be concerned about the head gaskets blowing, but need the original issue fixed first or too before believing it was just head gaskets if that is the next item on the shops order of repairs for you, something caused it to start to blow head gaskets in the first place if they are blown by now..