[iZ4vel]

My Z4 hadn't been run for about a year since it was involved in a minor front end accident.. Being that it sat for so long, I wanted to flush the all the fluids in the car (antifreeze was due for change too), I poured some coolant flush into the expansion tank, filled up the the rest of the system with tap water. Let the car run for about 15 minutes to get to temperature. Its usually 55*F out here in AZ right now so I knew it shouldn't have taken that long to warm up but it did. Before this flush I remember my car would heat to normal operating temp in about 5 minutes and my fan and thermostat would turn on when the needle went past half way, which it would do every so often. I allowed the car to stay on, hoping that it would go past the middle mark on the temp gauge but no matter what I tried, revving in park, a/c full blast, heater full blast, nothing made the needle move past half temp not the gauge, this meant the fan never turned on and the thermostat never opened. My fear here is that the engine temperature is actually wayyy hotter than the needle on the temp gauge is demonstrating.

Upper hose from expansion tank is always hot, I mean it gets extremely hot, but the lower hose the left side of the radiator is always cool to the touch.

1st thing I suspected was the coolant/oil temp sensor that's located on the cylinder head was bad and wasn't registering the temp correctly. Replaced it with a brand new part. Didn't help anything, needle still stuck at halfway.

2nd thing I suspected was that my thermostat was stuck open and therefore the car was taking so long to get to normal operating temp. Replaced that with brand new thermostat, again needle not moving past halfway, fan not turning on, and thermostat still not opening.

3rd thing I suspected was that the temp gauge needle was stuck and couldn't go past half way, I disconnected the coolant/oil temp sensor while the Z4 was running (cold engine) and that shot the needle into the boiling hot range where it actually turns on the red light, so I know the needle in the instrument cluster temp gauge isn't stuck and unable to go past half way.

UPDATE: I replaced lower hose coolant temp sensor with new part from autozone just now, again, top hose got extremely hot, lower hose cool to touch, cooling fan did not start, and needle did NOT go past exactly halfway.

All coolant/oil temperature sensors have been replaced, currently have pure distiller water in the system.


Could this be a computer issue? I have no check engine codes...

ANY ideas guys?? Thanks for the help in advance!