I’m seeing some interesting fluctuations in my coolant temps via my ScanGauge II that I *think* are I higher than I used to see. I did a search, but didn’t see anything that talked about fluctuations or the rate of fluctuation, so apologies if this has already been covered.

My “normal” behavior is to fluctuate between 200 to 207 over about a 10/12 second period while on the highway – i.e. start at 200, rise to 207 after 10 sec and then drop to 200. Lather, rinse, repeat. In traffic I see a similar pattern only the temps tend to go higher (usually to around 215 or so). I seem to recall that the temp was much more stable on the highway – usually hovering between 198-200.
Hard to tell on the highway, but it would seem that the fan is constantly working. Seems a little odd to me.

Is this normal behavior? Anyone else see something similar?

 

My coolant temps fluctuated 40-50 degrees depending on temps and traffic conditions. It's normal, and there's nothing you can do unless you run your AC all the time.

This is exactly why all coolant gauges in modern cars are "Dummy" and completely worthless. Because people freak out if they see it moving around.

 

Thanks Rusty
Yeah, I do get a bit paranoid – having had the car catch fire due to the PS pump shorting, having the whole shebang replaced, and then overheating 3 months later ‘cos the new PS fan failed *and* the dealer didn’t carry out the TSB to separate the PS fan from the rad fan, I’m a little twitchy when it comes to cooling!

 

that explains why mine never changes after getting up to temp, chrono pack, but tbf my oil moves a lot when i give it some beans, so one out 2 aint bad

 

I had heard the same about the gauges being "dummy", but I have noticed that mine (oil, coolant) do flunctuate slightly during normal conditions. But I guess the ScanGauge would be the best thing to use for accuracy.

 

IIRC the chrono oil gauge is real. On most modern cars coolant gauges are configured for a "Range" to indicate nominal operating temperature. Aka, anything from about 170 degrees up to 240+ doesn't move the gauge at all from the middle. Lower than 170 and the gauge is lower, (when the car is warming up). Higher than 240 and the gauge will start creeping up.

I have Navi on my car so I don't have any gauge at all, just a light. I've seen my temps go as high as 252 or so in traffic with no coolant light on the car. Most coolant systems will boil at 265 or so.

Scangauge II would be a good investment, not only for the coolant temps but for other gauges as well.

 

I have attached a file that shows a graph of my R50 coolant temp. The range is 222.8f to 204f. this is all while idling. On the R50 the fan comes on at 105c (221f and goes off at 101c (213f) this is by design. If the car is moving, depending on the speed the temp may not get that high.