Engine coolant temperature

2009 BMW 118I
190,000 MILES • 2.0L • 4 CYL • 2WD • AUTOMATIC
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VINAY NAIDOO
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  • 2 POSTS
Hi, i was under the impression radiator fan not working because my cluster showed 110 degrees Celsius when vehicle idling but fan was still off. Top radiator pipe was very hot and bottom pipe was warm when i checked. I purchased vehicle recently and put on machine nd diagnosed thermostat stuck in open position. On inspection noticed thermostat removed. I just had thermostat replaced. No codes at all on Icarsoft Pro diagnostic machine. I read a post on testing fan via coolant temperature sensor that's on radiator outlet pipe. Removed sensor , blocked pipe, ran engine and after a minute placed sensor in a cup of boiling water and fan turned on. Please note vehicle doesn't have a temperature gauge so I have to either plug in machine or use cluster code to open temperature readings. Is it normal for the engine to reach that temperature without fan coming on or is there a problem with wiring circuit ?
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Jul 9, 2021 at 1:17 AM
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JACOBANDNICKOLAS
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  • 110,175 POSTS
Hi,

The cooling system thermostat is designed to open fully at 195 degrees F (90 C). However, the fans will not usually actuate until the engine temp reaches between 107 and 110C.

If you allow it to continue running, will they turn on at that temperature? Take a look through this link:

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

Also, if you open the radiator when the engine is cold, does it appear to be clean inside? There could be a blockage as well.

Let me know.

Joe

Jul 9, 2021 at 10:05 PM
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VINAY NAIDOO
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Hi, thanks for the advice. Opened radiator when cold and it is clean inside. Took the car for a short drive and once back opened hood and noticed fan was running. Plugged in diagnostics tool and error shows up as temperature too high at coolant temperature sensor at radiator outlet. Felt pipe with hand and noticed it was warm but not as hot as top radiator hose. Cleared fault. Switched off vehicle and after 15 minutes started it again, plugged in diagnostic tool and noticed no fault codes showing. I will still be doing a total radiator flush and replace coolant as well and test further to confirm everything is running smoothly now. Will keep you informed.
Jul 10, 2021 at 6:35 AM
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JACOBANDNICKOLAS
  • CERTIFIED EXPERT
  • 110,175 POSTS
I think that is a good idea. My concern is the idea that the thermostat was removed when you purchased it. People usually do that because of an overheating issue.

Do what you mentioned, the flush. Here is a link that you may find helpful:

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

Keep in mind, it isn't odd for the upper and lower radiator hoses to feel different as far as temperature. The radiator is cooling the antifreeze.

Let me know if the flush helps or if you have other questions. Also, take a look through this link. Don't be alarmed when you see the title. LOL, I want you to do a couple of checks related to a bad head gasket.

https://www.2carpros.com/articles/head-gasket-blown-test

I'm just suggesting the basic tests in the link because a blown head gasket can cause overheating as well.

Let me know what I can do to help.

Take care,

Joe
Jul 10, 2021 at 9:19 PM