95 K3500 runs hot in hot weather

[94GMC2500]

My 95 has a good stock radiator, it's about 2 years old, dual thermostats, late water pump with screw on fan clutch, Hayden 2840 fan clutch, late 6.5 fan, 180 degree T stats. It will stay about 180 degrees towing our camper with outside temp up to about 80 degrees. This weekend I pulled the camper when it was a little over 90 degrees and water temp ran 210 to 215 degrees and wouldn't drop when sitting and idling. The trans temp gets up there on hot days too. The fan clutch is a little over a year old and comes in at a pretty low temp and I can hear the fan on cooler days. I don't hear the fan roar on real hot days though. Will the fan clutch not spin the fan it the temp gets to high? Would the Hayden 2886 fan clutch work better? Also my truck don't have that baffle thing under the front of the truck that goes from behind the bumper down to the crossmember. Could the affect the cooling? I think some of the problem is the hot air can't get out from under the hood fast enough. The stack is clean.

[DmaxMaverick]

Revisit your thermostats. It/they control the fan clutch (if the clutch is working right, regardless of model number). 215F is well below any alarm temp, so if you can keep it there, it's fine. Problems happen when it runs well above that and you can't control it.

[Robyn]

Another thing to take a look at.

Plug in a decent scan tool and compare the temp it shows to what the gauge shows....

The actual engine temp may be different.

The gauges on these are not always perfect ...As Maverick mentioned the temps you are seeing are not alarming....
20-30 degree variation in gauge readings can be common.....And a 1995 rig has seen a lot of wiggles on that temp gauge.

Try replacing the temp gauge sender with a NEW AC DELCO part....see what shakes.

Stay away from the aftermarket stuff....

[94GMC2500]

I am sure if it pulled a hill it would have climbed more than 215 degrees. I have read that restricting the bypass helps it cool better, is that true? I have a heat gun I can aim at thermostat housing to see how it compares to the gauge. I don’t have a decent obd1 scanner, I don’t know anyone who does.

[DmaxMaverick]

The problem isn't how hot it gets, so much as how it's controlled. 215F as an operating temp is OK. Pulling a grade and seeing 230F is OK. What happens after is important. As long as it's able to limit the upper temp, and control it after a workout, it's OK. As Robyn said, the gages aren't that accurate, so should be used for tracking trends more than actual empirical data. The senders aren't that costly or difficult to replace, so the easiest remedy is to just replace them, if they aren't confirmed accurate or are very new. Gages and senders get tired with use, and become less accurate as time passes. If you are hearing the fan clutch engage, then the thermostat(s) are working. If you are concerned the temp is too high when that happens, replace the thermostats. Use only OEM or Robert-Shaw stats, at the temp you want. Off-brand stats don't work as well. If you can't find them locally, www.kennedydiesel.com (http://www.kennedydiesel.com) has them.

[More Power]

....I don't hear the fan roar on real hot days though...

That's the problem... If you have a water pump with a screw-on fan-clutch you can use the early Duramax fan-clutch and a 21" 9-blade composite fan.

Here's a link to a page that discusses what these 6.5's are capable of (regarding cooling and other stuff) when set up correctly.

https://www.thedieselpage.com/finale.htm

Here's an excerpt from that piece:

During the Ohio trip, we encountered ambient temperatures of up to 105° Fahrenheit. Whether towing uphill, downhill, on the flats or while crossing the Continental Divide, the engine temperature gauge never exceeded 205°.

Where I-90 crosses the continental divide (Pipestone Pass) has miles of 6% grade from either direction.