temp gauge goes down when heater turned on

[pbonsalb]

I would expect “turning on a second radiator” albeit a small one, to drop the temp. It’s an age old trick for an overheating car — turn the heat on full.

[Beamerdreamer07]

I would expect “turning on a second radiator” albeit a small one, to drop the temp. It’s an age old trick for an overheating car — turn the heat on full.

But what is to keep the temp steady even with the air on full blast driving down the road? This makes no sense to me lol it's frustrating. 🤬 the only thing I can think is there isn't enough coolant. I just looked again and the stick didnt pop out of the coolant tank. So it may just be a little low. May have been a lot of air in the system and it finally worked it's way out and just need to top off. I'll try that tomorrow and see if anything changes. Just hoping I dont have to replace the thermostat again. That's a pain in the a@#. It's a E83 so its located in a blind spot basically on the lower left corner of the engine

[pbonsalb]

I don’t know the E83 but is it a self bleeding system with tank higher than highest coolant passage or is it low mount like in the E36 that requires a bleeding process? A system not fully bled will cause problems. The proper stick reading may change depending on whether coolant is hot or cold. Some thermostats have an air hole that should be placed at the top. Others just have a jiggle pin and I don’t think orientation matters. I assume it’s not possible to install the thermostat backwards.

[Beamerdreamer07]

I don’t know the E83 but is it a self bleeding system with tank higher than highest coolant passage or is it low mount like in the E36 that requires a bleeding process? A system not fully bled will cause problems. The proper stick reading may change depending on whether coolant is hot or cold. Some thermostats have an air hole that should be placed at the top. Others just have a jiggle pin and I don’t think orientation matters. I assume it’s not possible to install the thermostat backwards.

I pulled the cap off, or screwed you could say, right after I started the car last night for work. The stick didnt pop up at all and I know for sure it was cold. (20 degrees out) so I should probably assume that it had air in it and it worked itself out. The thermostat has 3 maybe 4 coolant lines that go into it and from it. Only one way to put it in. The thermostat housing then bolts to the water pump. Dumbest engineering ever lol. But the tank is higher than the rest of the coolant lines and radiator. At least the cap is for sure. I just got home so I'll let it cool down and check it out this afternoon. It's just crazy that the temp drops damn near as soon as I turn the blower motor on. And like I said I'll have the blower on the lowest setting driving down the road and it will just drop the temp faster than crap. I assume that when you turn it to heat and activate the blower motor it activates a switch that allows coolant into the heater core and so the rush of what amount of coolant I do have in there drops the temperature due to air in the lines maybe...idk I'll def check it out like I said though.

[pbonsalb]

I hope you don’t have a warped cracked head from a past overheat. Many years ago I had a different car that would exhibit what you are describing and it had a cracked head.

But it seems like you are running too cold, not hot, and a warped or cracked head would cause an overheat.

[Beamerdreamer07]

I hope you don’t have a warped cracked head from a past overheat. Many years ago I had a different car that would exhibit what you are describing and it had a cracked head.

But it seems like you are running too cold, not hot, and a warped or cracked head would cause an overheat.

Yeah I dont think that's my case here. At least I hope not. It's never over heated on me or gotten close.

[arda5445]

I'm having the same problem. Have you found any solutions?