Engine running hot - sustained temps between 206 and 216. Need to troubleshoot.

[AdventureBuddies]

Scangauge reads "normal temps" around town 190 +/-. However, while driving on the freeway it climbs into the 200s and with any sustained incline, temps quickly go to the 220s.

I monitored it closely in Death Valley this weekend. Here's what I observed with ambient temps in the high 90s, truck is built and weighs around 6800lbs and has a Maggiolina on top:

1 - 218 to 229 leaving the valley (that's 50mph, 2200ish rpm, 3300ft of gradual elevation gain.

2 - once over the pass, temps dropped reletively quickly to 200 +/-.

3 - on flat (occasional slight up or down) temps hovered between 216 and 222.

4 - A/C cuts out when Scngauge reads 222 and comes back on at 216.

5 - temps reach 220-226 on every sustained uphill, even when they are not steep - basically it gets hot any time the engine is under load.

6 - Once over the Cajon Pass and driving in normal ambient temps (around 80) temp never dropped below 200.

So, I obviously have a heat issue. Here's the relevant PM I've done:

New thermostat, radiator, blue hub fan clutch (not modified), all belts and hoses, water pump, 50/50 green coolant, and evac and refill A/C freon (A/C works fine)

I didn't have the Scangauge before doing all that work but I believe I was having the same problem because the A/C cut out on me- so don't think I caused the problem with the PM.

Obviously the first two things to do are check for correct thermostat operation and mod the fan clutch. But from everything I've read, modding the fan clutch might knock off 5 deg - not enough to get me in the normal range. So, I'm at a loss on what to check next.

Is it possible that I have a bad temp sensor and that's it's giving the computer the wrong temps?

[john_eckels]

Assuming you used OEM parts, the usual things that cause this problem have been replaced. Has your truck been flushed recently? There may be a flow restriction inside the engine. When I had my bad thermostat, there was a temperature difference of 75 to 100 degrees F between the inlet and outlet hoses on the radiator. If you use an infrared thermometer to measure these 2 points you may get an idea if the radiator is doing is job properly.

[HomersCanyonero]

This is a conundrum. You essentially have a brand new cooling system, yet you are running way too hot as far as the computer is concerned.

You need to verify that you are in fact running hot.

Other than that...I have no idea what your problem might be.

[elhombre]

Sure sounds like your radiator is not up to the job. Have you driven through mud or possibly have something stuck in between the A/C coils and the radiator? I would say that your sensor is working fine because the A/C cut-off switch is independent of the temperature sending unit and the numbers seem correct. When your A/C cuts out, you should hear the rad. fan getting after it. If you don't, the fan clutch isn't working right.