Cheers everyone,

just got back from a 1000 mile road trip, everything was fine with my truck.
But today I did some work (replaced some control arms and ball joints), when driving home I had the OBD live data on my screen.
I noticed the coolant temperature rising up to 108°C / 226°F while driving along (20/30mph). I never noticed such high temperatures.
I kept driving as I was close to my home. Temperatures were dropping again then, down to 94°C/201°F. I let it idle in my driveway and temperature was stead at 94C/201F.
Is this anything to worry about? Maybe the thermostat giving up?
Only things I changed recently is the drive belt with the tensioner.

Thanks a lot!!

 

If you started with a cold engine, that isn't unusual.

 

Yeah, started cold like 3 miles before that.
What is the reason for that?
And thank you for always answering the questions, even if they are somewhat stupid sometimes.
I am really happy about that!

 

No such thing as a stupid question here.

There is probably some law of thermodynamics that would explain it, but, damned if I know what it is. It's just behavior I am used to seeing. If it runs hot like that for longer than a few minutes though, I would be tempted to swap the thermostat. I don't think its necessary yet at this point though.

 

OK, maybe it happened before and I just didn't notice. But will now keep an eye on it for sure.
Thanks for the explanations!

Have a great day and many greetings from Germany

 

I nearly forgot about it, but today I noticed the gauge going up and down again and checked via OBD.
So, no real matter how I'm driving, temperature goes from 92°C/198°F to about 104°C/219°F and back down.
Even when going steady at 60mph.
I think I haven't had that before?!
So it seems like the thermostat is not operating like it should?

 

They aren't really expensive, could just replace it, see if anything changes. (no "safety stats" though, those are guaranteed to fail.)

 

Yeah, maybe that's the best idea. Will have to change over my coolant anyway, so can do it all together then.
Will a "Gates" thermostat with 203°F be fine? Like " GATES34053S " ?

 

If that is the stock temp, then sure. Gates generally has a pretty good rep.

 

How long does it take to change?