How are reading the lower hose temp? Scanner? IR thermometer? Hand?

My scanner will read the sensor in the lower hose.

It's normal for the lower hose to be much cooler than the ECT/upper hose as it's the cooled water coming out of the radiator. It should be "quite warm" however.

The fan shouldn't kick on under normal conditions unless you are standing still for a good while or ambient is quite high.

What's your ambient temp?

also, there should be very little radiator flow until engine gets to operating temp and the tstat opens which it seems like that is working properly if the temp stops rising.

The values seem a little high but i don't remember what the m/n 62 motors' normal tstat temp is but 190 comes to mind that might be the optional low temp model.

My crazy car n55 runs at 228 cruising and 198 under load.

It sounds like tstat not opening fully and you're getting enough air-cooling from the blast of the aux fan on the block or the stop leak plugged the radiator.

If was my car with the symptoms you describe i would pull the lower hose (Clamp it close if you have enough length to do so to keep the water in the block) and see if the radiator drains quickly and add distilled water into the upper hose to flush the radiator. It should come out as fast as you can pour it in.

Forgive me if your engine doesn't have the same lower hose setup my inline six had. Which motor is in that car? I think it must be the n62.

–awr–

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)