04 silverado 117k temp'ing up then correcting itself.
Typically my 04 silverado v8 5.3L with 117k miles usually warms up to about 210 (or slightly less than 1/2 the gauge) and holds the temp. Lately, it has been temping up to over 210, then falling back down and holding them temp. This worries me because its a-typical behavior and in the past i have heard from a mechanic (while i owned a diff car that had over heating probs) that you want your car to temp up and hold a temp. no fluctuations. This worries me as it has just started happening (with no other issue to blame) and i dont want it to persist.
I should add that i have not had the vehicle's 100k mile service yet (plugs, wires, coolant flush, etc. have NOT been done, i cannot afford it and dont want to do a coolant flush myself lest i make the situation worse) but that made no difference in the 100k-115k interim, so why now would the truck begin to temp up then go back down and hold? God forbid it one day does not hold its temp and actually over heats. Are there any fail-safes in place that will save me from smoking the motor if it does decide not to hold its temp and actually over heat? I can only guess that it temp'ing up then going back down and holding is from the radiator kicking in but it never did this in the past.
Also im going to be taking a closer look at this problem so that I can accurately describe it better. The over heat (if you can call it that) only appears to happen on the first start of the day, subsequent cold starts (like the 2nd start after an 8hr work day) do not seem to have this over-heat-then-steady problem as the 1st start of the day has. And it also only appears to happen on "colder" days, as hot days dont seem to affect it (this is only my hunch and i cannot confirm this 100%)
Anyways, any help is gladly appreciated.