What have you CHANGED on your cooling system?
The 98 D1 got a looking into using a probe camera. We found the INSIDE of the radiator was CLEAN almost looking new. We went to the 180 stat and Royal Purple Water Wetter. ALSO burped the air 3 times including the heater. There are 100% all new hoses. The results where 182 to 194 NO A/C 195 to 202 (1) A/C on and 201 to 208 with (2) A/C units on. This has rear air.
With the HIGHER temp than you I am think SLEEVE damage. The P38 got a rebuilt engine and 100% new cooling system it it NEVER gets above 194 with the Air on and about 202 in traffic.
Is your engine rebuilt or the original one untouched?
PS the temp gauge on the 98 NEVER gets above 9:00 at ANY TIME so is the UG just TO good and playing with our minds?

 

I replaced my fan clutch with the Chevy one from the tech section 2? years ago, original radiator, all original engine.
I replaced all the coolant hoses when I got the truck back in '07, I also replaced the t-stat at that same time.
I change my coolant every 2 years, thats all I do.
In my opinion your trucks temps are fine.
My temp gauge never goes past 9:00 either.
The UG is a fun tool, I dont spend to much time watching it anymore, it is part of my gauge scan but only for the engine temp and RPM.

 

Mr. George,

Did your snake camera get all the way to the bottom of the radiator? If the lower rows are restricted, they will measure cooler than upper rows with an infrared thermometer. Could be buildup inside, not on ends where camera would see.

I drove mine with 180F yesterday 180-183 with air on (single) at 55-60 mph. It will get to 187 sometimes at 70 mph. So either coolant sensor could be out of range slightly, or radiator is not keeping up with the heat load. Maybe some cooling system ports inside engine need flush as well. Hopefully no grease on fan belt making water pump turn slower. Good water pump - BP Utah has some after market ones with larger bronze impeller)?

While Spike is correct that temps are in acceptable range for the engine, they are above what I would expect for your 180F; you may want to re-visit the radiator. Obviously temps warmer at extended idle and slow traffic. Might also check refrigerant levels in AC system, high head pressure could translate into more heat than expected.

And certainly there will be variation between individual trucks. My oldie has a rodded out radiator, a used water pump, a chevy fan clutch, and an oversized fan. Fan may make more of a difference at slow speeds. But at freeway speed, the 50 mph breeze is way more cubic feet per minute than the fan.

Also, you and I both know it will be warmer this summer is this part of the world. Augusta or Macon usually have the highest temp in the state in the summer. Pix shows that my gauge reading vs OBDII port, your results might vary.

 

Camera went to the BOTTOM on the vent plug side and into the hose side. We drained the system down and took a SECOND look and the darn thing looks new on a color camera. Also on that page is the 1996 truck I will be parting out. http://www.leathercarebyleatherique....previous-photo

 

i would be willing to bet that there is some tolerance stackup between the old wiring and old sensors that it would be difficult to compare one to another and expect much closer results.

if spike is seeing 199 peak and youre seeing 202, thats a difference of less than 2%, which seems damn good considering...

 

But Spike has a 195 F stat and George has a 180F stat.

 

the plot thickens

 

I have a 180 stat and sometimes the temp nearly reaches 200 before rapidly dropping to 177-180.

 

the plot thickens indeed...

my next hypothesis -
there has been much ado about thermostat variability as of late on the RROC boards, and some have found "out of the box" variations on new parts of fairly significant margins. 10%? probably not quite... but my guess is if george tested his 180F tstat there might be some lag time there before its fully opened.

and by tested i mean removed from car for testing in a pot of water, not testing with a heat gun in the car.

 

Yes I know about that since our 1978 SS2 was a tea kettle when we got it. Stat was STUCK shut. Never did any damage since it was watched like a hawk when we first got it after losing an engine in a 1971 SS1.