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  #1  
Old 02-01-2026, 10:50 AM
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Odd question...

Today's temperature was 32.5c and in stop and go traffic (max 25kph down to 5-6kph) my intake temp slowly climbed to 68c, but my coolant temp went from 103c down to 93c. After 10km I was driving at 140+ and coolant went back to 103c and intake dropped to 44c.

Can anyone think of a reason for such drastic changes? I could understand coolant dropping and a slight rise in intake temperatures with no load on the engine, but I'm concerned about some sort of electrical gremlin and if I have zero clue where it would be that screwed with those two sensors.

Thoughts? Ideas?

Thanks!

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Old 02-01-2026, 11:54 AM
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Slow driving will bring up intake temp that's normal.

Cold temp can/will drop if the fan kicks on and the DME opens the thermostat.

On my n55, the map tstat is far more active than my m54 and I suspect m/n62 but those values would not surprise me at all.


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Old 02-03-2026, 10:29 PM
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Quote:
Originally Posted by andrewwynn View Post
Slow driving will bring up intake temp that's normal.

Cold temp can/will drop if the fan kicks on and the DME opens the thermostat.

On my n55, the map tstat is far more active than my m54 and I suspect m/n62 but those values would not surprise me at all.


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I agree about the temperature rising, but never that high (at these low air temps) and never watched it climb like an elevator. That's why I am worried it is something in the system.

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Old 02-03-2026, 11:29 PM
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Bad clutch on the main fan would cause the symptoms


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Old 02-04-2026, 12:37 AM
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Quote:
Originally Posted by andrewwynn View Post
Bad clutch on the main fan would cause the symptoms


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Simple test to find out. Stick a rolled up magazine or newspaper in the fan while running. If the clutch is bad the fan will stop.
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Old 02-04-2026, 01:32 AM
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True on fan test, but my coolant temp dropped 10c at the same time.
Just something else to confuse me and will probably be some strange crap that will bite me in the ass at a most in-opportune time.

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Old 02-04-2026, 01:44 AM
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Originally Posted by EODguy View Post
True on fan test, but my coolant temp dropped 10c at the same time.
Just something else to confuse me and will probably be some strange crap that will bite me in the ass at a most in-opportune time.

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Could the aux fan have kicked on?
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Old 02-04-2026, 04:24 AM
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Quote:
Originally Posted by Fifty150hs View Post
Could the aux fan have kicked on?
Nope, I don't have an Aux fan installed... Crazy right? Especially with temperatures over here, yet my max temp (coolant) is 105c.

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Old 02-04-2026, 07:54 AM
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Is it possible that the thermostat map cooling activated due to high intake air temp and deliberately lowered the coolant temp?

This characteristic map is determined by the following factors:

*Engine load
*Engine speed
*Vehicle speed
*Intake temperature
*Coolant temperature
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Old 02-04-2026, 08:01 AM
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Quote:
Originally Posted by Clavurion View Post
Is it possible that the thermostat map cooling activated due to high intake air temp and deliberately lowered the coolant temp?



This characteristic map is determined by the following factors:



*Engine load

*Engine speed

*Vehicle speed

*Intake temperature

*Coolant temperature
Now that's a distinct possibility and since I have a Gulf edition, the map settings could be crazy in their values...

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