Overheating

You should be able to see daylight thru radiator/ AC condenser/ oil cooler stack. If not, you may have accumulation in the space between them that is killing cooling capacity, and it may have been driven there by dealer's guy blasting the radiator (don't know if that was done) less than completely.

Dealer may have (though should not have) put in one of the cheazy aftermarket thermostats w/ only 0.8 sq. in. of flow area each (vs. almost double that for good ones). I got one of these over the counter at NAPA last week, and compared it to TDP article photos; I'm pretty sure I'd be overheating ASAP if I installed it. See what part # they show as installed (not proof that's what went in but better than somebody's word) & look @ one out of dealer stock to see you've got right tstat unit.
180 tstats, tho maybe a good idea, won't do anything for overheat like this (absent bogus stats per above); once stat is open- its open & flowing to extent it can so 180 or 195 would be open at these temps.
Based on description of driving vs. heat, I'm inclined to believe gauges you've got, & that heat is real. Likely either loss of cooling capacity @ radiator due to service process, or constriction on coolant path getting to radiator (stats, passages in heads/block, hoses or pump). if you're losing coolant, might be hose leak, head gasket or pinhole in radiator.

UC DAVIS might be onto something w/t-stats..the "flush" may have stirred up a big crud-ball and restricting flow...i would get your $ back on the resevoir,the resevoir doesnt hold the pressure..the pressure cap does....if you're 100 percent that you have boost give UC DAVIS post a good reading at...its probably going to end up being one of those easy things that can really mess things up...in realistic theory i would start "undoing" what the dealer did...good luck..i hope the DP solves this for you ;)

Another thought if shopping for service- I've got a great radiator shop in my neighborhood. They do hot rods, industrial radiators, & the usual consumer car stuff. They are the go to guys for race rigs. You've probably got one like them in the near vicinity. Most of these guys do whole cooling system work, not just servicing the radiator (stats, hoses, belts), but don't do much beyond cooling.

Don't your later trucks have only one MAP sensor for telling the computer what the elevation is? My truck has two (OBD I). I don't think this will turn on the SES because the computer thinks everything is fine. If the truck pulls good below the hills then the computer might not correct for the elevation changes? I think any reader will tell you what the elevation above sea level is, you might have to subtract 15 from the number to correct for the pressure at sea level.
If the dealer steamed out the radiator they might have bent the finns over. If the knuckle head saw silver he might have thought he was doing a great job and removing ALL debris when he was actually bending the fins over?

I HAVE NOTICED MY TRUCK RUNNING HOTTER THAN I WOULD LIKE TO SEE WHILE RUNNING THE AC. THIS SUNDAY WHILE HAULING ABOUT 6500LB IN 92 DEGREE TEMP WITH AC ON SHE WENT TO 210 AT 70MPH ON A GENTERL GRADE, I WAS WATCHING IT REAL CLOSE. I BACKED OFF AND THE FAN THEN HIT HARD LIKE AN AIRPLANE AND PULLED DOWN TO BELOW 200 AND I TURNED OFF THE AIR. THIS CONDITION SEEMS TO HAPPEN WITH THE AC ON. THE AC APPEARS TO RAISE THE TEMP BY 15 DEG IN HOT WEATHER. I THINK MY FAN DOESNT HIT AS EARLY AS IT SHOULD. FRANKLY I WOUULD NEVER LIKE TO SEE MY ENGINES OVER 205 DEG. DOES THIS SOUND RIGHT

I second on the t-stats. The only thing I would run is Robert Shaw brand Part #330-180 for your rig IIRC. They'll flow a ton more than a disc type t-stat.

One thing to check is the temp where your fan clutch is kicking in (if at all). Look at the front of it at the bi-metal spring. Is it covered with a 1/2 inch of grease and grime?

I noticed the EXACT same thing as Gary Page mentioned above. A/C on = 10 to 15 temp increase like right now. Since doing the dual thermostat cross over (w/RS 180 t-stats), new fan clutch and 21" composit DMAX fan conversion....things got WAY better.

I would REALLY recommend you get gauges. It's scary to think what EGT's you may be hitting if the water temp is pushing 260*! After having boost/egt gauges you'll never even consider driving a 6.5 by the coolant gauge!

If you ever find grease or oil on the front of the fan clutch it's toast.

I had the same problem on my 98 Suburban. I just bought a 21 in fan and fan clutch from Bill Heath and towed my 7500lb trailer in 90 degrees and A/C on and temp guage went up to 205/210 and fan clutch kicked in and went right down to 190 deg until I hit a hill again and same results. Before installing my tems went uo to 220 to 230 and then kicked down and stayed around 200. Excellent product!

I had the same problem on my 98 Suburban. I just bought a 21 in fan and fan clutch from Bill Heath and towed my 7500lb trailer in 90 degrees and A/C on and temp guage went up to 205/210 and fan clutch kicked in and went right down to 190 deg until I hit a hill again and same results. Before installing my tems went uo to 220 to 230 and then kicked down and stayed around 200. Excellent product!

these are all good sugestions, so let me add one more.
If the dealer's service tech got the ratio of antifreeze/water way, way off, this will affect the heat transfer rate. water has a much higher rate of heat transfer than "antifreeze". if the cooling sys contains too much anti-, higher cooling sys temps will result.

my opinion is: it worked fine before they worked on it, and now it runs hot.......something went wrong while your truck was in their hands.
Who posted "redo what they did", ? that gets my vote.

Here's another option: check the water pump flow and belt tension. It's not unknown for a water pump impeller to start disintegrating.

Airlocks can also cause overheating, but the GM cooling system is pretty good at self bleeding.

I too would put 100 bucks ;) that the antifreeze concentration is way too high. This will kill the cooling system capacity by half, lower the boiling point and will not provide the corrosion protection as it needs water to work.

Did anybody check it? :rolleyes:

Thanks again for your guys input. Have another appointment on Wednesday and again I am going to give them your posts and have them check each one of the issues out.

If you now have black smoke and you did not before like others check the waste gate control. Another thig if you are lacking power and if its boost related that can also cause the temps to be high because youare not pushing the same amount of air through the engine. The air helps keep it cool as well. When I jacked up my boost egt's came down which will in turn cause it not to heat up as much. All these mods are great but if you did not have a problem before there is know need to change anything. First get a boost gauge so you can see for sure what kind of boost you are producing. Check the anti freez concentration although I bet its fine. T stats by all means I would change those to Robert Shaws but I would use the 195*. I will get flamed for saying that I am sure but I have tower my 5th wheel all over the USA and have desided the 195* make the truck perform better than 180*. I am not alone on this as I beleive JK found the same thing. Not only that if you are having and over heating problem colded stats won't matter any away. Mine is a 95 and I have never had any over heating problem except when the fan clutch got weak.

Greg