Just been out today on a freeway type 60 mile cruise at about 60-70 mph.
It was VERY WINDY and a lot of drag on the truck was evident.
I wasn't towing anything.
Today I noticed that my temp gauge was moving from a needle thickness below half way, which is normal all the time for my 75,000 mile Hemi, to about 3/4 of the way to high, then back to just below 1/2 way again.
It was cycling between the two all the time, taking between about 3-4 minutes, between the lower and higher readings.
I've not noticed this on my Hemi before and whenever I've looked in the past, it was alway rock solid, one pointer thickness below 1/2 way.
Any ideas???

My oil is ok no emulsion etc, no loss in performance and no bubbles in the coolant.
I did have a coolant leak about three months ago and fixed it with a "stop leak" type radiator additive.
It was the typical Hemi radiator problem where the seems on the rad have a slight split.
The reading on the temp gauge was always at just below 1/2 way until today.
This is it's first longish run out since adding the "stop leak" stuff.
My thoughts are,
1) ?? Radiator blocking up.
2) ?? Stop leak is causing somthing.

I think the thermostat is OK, as the temp ranges from low-medium high then back to low. I' m thinking this signals that the thermostat is working.

Any help is appreciated

 

Or---it may be time for a new stat--just a thought--or the water pump is going--I like the stat idea first--its a lot cheaper.

 

Just changed out my termostat and put in a Mr Gasket 180 degree.
At the same time, I replaced my radiator as the old one had a small leak down one of the header sides.
I flushed out the system and replaced all the anti-freeze and used de-ionised water for the re-fill.
Whereby the truck used to have a temp of one needle width below halfway when it ran normally, which then progressed worryingly to halfway then over by 4 needle widths, and cycled between the two over a 4 minute period, I now have a Hemi which runs at a solid 1/4 of the gauge at all times.
I'm such a happy chap now that everythings running nice and cool!
Plus, I have the satisfaction of doing it all my self, saving a whopping amount of money.
I used Moe's performance for all my bits and he shipped them all to me in the UK in under a week.
Great service!
Al.

 

Stop leak is more of a quick fix to get home, not a permanent fix (I personally would never use it). Should fix the leak the right way, replace the failing component, then flush flush flush.