I looked at a few other posts before deciding to post but everyone I looked at had 'low/no coolant' in there somewhere. So I felt making my own would be better.

So my R53 is fine when driving.
When idle for more than 3-5 minutes my temp gauge peaks just enough to turn the high fan on. As soon as I drive it will either go down slowly or it'll jump down half way and then slowly come back up.
Coolant level is good with no leaks and my heat works fine at all times.

What do I need to be looking for to solve this?

 

Sounds like the low speed fan isn't coming on. If you turn the ac on the low speed fav should come on. Common problem unfortunately.

Nik

 

You wouldn't happen to have a scangauge or something similar world you? Low fan comes on at 222. Both at 235. Mine will start up after a few minutes idling like at the drive thru but go off shortly after.

 

I'll have to listen for low-fan.
I think it comes on but I can't be certain. I'll let you know this afternoon though.

No scangauge. I have chrono pack though. Not that it tells your exact temp but it kinda helps. It's a gradual crawl into the 230s and then it kicks on. I never go up to 250 and beyond.

 

The low speed fan is very quiet....that is WHY the first sign of failure is you start hearing the high-speed fan kicking on....
Let the car idle in your driveway with the hood open for a bit after a drive home.... And check to see if the fan is coming on....
While the high-speed sounds like a airplane or lawnmower reving up....the low speed is about as quiet as the car ..just a muted hush....
The high-speed fan is a last chance of the car that prevent overheating...in normal use you should NEVER hear it unless is it blazing hot and you have very little airflow....like stuck in traffic on a 100°+ day or you drive a canyon road hard and stopped at a rest stop....
So I'd bet 90+% that is your issue....
Other options are not as pretty, simple or cheap to fix if you coolant level is good.

 

P.S.
The fan should go from off....to low speed... To hi...then to low....mataining temp when idling on a hit day, not moving...
If it cycles on/off to high-speed....the resistor is burnt out on the fan...

 

Alright so I got in a good 20 miles of drive time. It's 85*.

When the AC was on my car went from loud to louder.
And without the AC it was still loud.
I know high kicked on but I don't think I heard low.

How hard is it to replace the resistor?

 

I've got the chrono as well, I monitor everything with a scangauge though. Under normal operation the needle sits at noon and moves up maybe a needle width before the low speed fan comes on. If you're getting up to 230+ the low probably isn't coming on. High comes on at 235f. If the fan is coming on at low and not able to keep things in line it could be something like a dying water pump, or possible sticking thermostat.

 

er....open the hood and look......be sure. lol

 

Recheck shows spinning only in jet mode. D:
Do you happen to know what the average lifespan is of the resistor?

 

Not long enough...lol...
Many OEM ones were failing in 30-40,000 miles....
My solution was to get a TYC branded aftermarket one (exact fit) for about (was $85 when I did mine) $100, and swap it out.
Rockauto.com had the best prices about 6 years ago when I did mine...
The resistor mod usually request the fan be removed or you hack the cars wiring up to do the change....

 

Figures.
Would it be easier to just replace the whole assembly?