Another Aux fan question- '01 3.0 Coupe

[ixlr08]

I am considering doing the fan delete to my new to me, 01 3.0 coupe w/M54 engine and I am trying to verify my Aux fan is working correctly. I have read numerous threads on this issue, but different engines get mixed into the thread and creates confusion. I removed the fan to do the serpentine belts and I have not replaced it yet. RealOEM indicates I should have the 91/99C temp switch. If I turn on the AC, the fan goes on and off, low speed, when the AC compressor does. If I jumper the pins on the temp switch connector, I can get both the low and high speeds to work on the Aux fan. BUT, when I just let the engine idle and heat up, I am using INPA to monitor the temp, I let the temp get to 105C(221F) and the fan has not come on yet. This seems to me to be an issue with the switch, but I wanted to verify before I go any further. Or should I let the temp go higher before I get concerned? If so... how high?

Thank you,

[danomite]

The radiator temp switch is monitoring the temps of the coolant on the cold side of the radiator...INPA is showing you the coolant temps in the engine at the temp sensor located in the back (see: firewall side) of the cylinder head. Do not confuse the temps! The "safe/normal" operating range (as per BMW) for our cars is up to 115C. If you're getting anywhere near that, and the aux fan isn't triggering, then you have an issue.

If you've verified that the radiator switch is in working order, and the fan is operating in both high and low modes, then overheating issues could be stemming from a defective thermostat...although I believe our T-stats fail in the 'open' position (which would mean you have something else going on...like a leak).

Randy should be able to answer this in his sleep. LOL.

[328 Power 04]

Ya, he's going to say you have air in your cooling system, or radiator.

[ixlr08]

The radiator temp switch is monitoring the temps of the coolant on the cold side of the radiator...INPA is showing you the coolant temps in the engine at the temp sensor located in the back (see: firewall side) of the cylinder head. Do not confuse the temps! The "safe/normal" operating range (as per BMW) for our cars is up to 115C. If you're getting anywhere near that, and the aux fan isn't triggering, then you have an issue.

If you've verified that the radiator switch is in working order, and the fan is operating in both high and low modes, then overheating issues could be stemming from a defective thermostat...although I believe our T-stats fail in the 'open' position (which would mean you have something else going on...like a leak).

Thank you for info on the location differences between radiator temp fan switch and engine coolant temp sensor. I will have to see if I can find a way to monitor the temp of the fan switch. I wonder if my IR temp gun would be accurate enough? I will have to give that a try.
I don't know if the switch is working or not, that is my question. But from your information about 115C being within BMW's normal range and I only let it run until it got to 105C, then it sounds like I need to let it run hotter to verify the operation of the switch.
Presently the car is not overheating, I am just trying to verify the aux fan is working correctly before I decide about going "fan delete".

[ixlr08]

With the help of the info in this thread it looks like I have answered my question, at least as far as the fan low speed functionality is concerned. I tried to measure the body temp of the fan switch thinking that would give me a good idea of if and where the switch was coming on. But the body seems to be a good deal cooler than the radiator temp so I gave up on that. I used INPA to measure the engine coolant temp and I used a thermocouple to measure the radiator temp. I put the T/C on the top of the 'cool' side of the radiator, gently shoved it down the hole in the top on the far right side and the fins held it in place. I let the engine idle until it got hot, when coolant temp read 106C and the radiator T/C read 100C, the fan came on low. The fan ran until the T/C read 66C and coolant temp read 99C. I let this cycle continue for 5 cycles and it was consistent. Based on this, as long as my Scangauge reading doesn't go above 225F, I will consider things okay. 106C=223F.
Based on these results, I will proceed cautiously with the fan delete and not put the fan back on now that the serpentine belts have been changed.