Coolant temp creeping to 218 on Fourth of July Pass, Cummins 450, is it my side radiator?

you're not worrying about nothing but you're not in trouble either. an ISL will run 210 to 215 on a long pull in heat all day and the fan is doing its job if you hear it. what got my attention is the change from last year. same engine, same hills, ten degrees hotter. that's almost always the air side, not the coolant side.

on your coach the charge air cooler sits in front of the radiator in a stack. dirt and road film and oily mist from the crankcase vent all land on the CAC first, then whatever gets past it packs into the radiator fins. you can look at the outside and it looks fine. shine a light from the engine side through the core and you'll see.

how to clean it without wrecking it: open the radiator door, spray a degreaser that's safe on aluminum from the engine side out, Simple Green or the purple stuff from the truck stop diluted, let it sit ten minutes, then rinse with a garden hose from the inside pushing out. no pressure washer, ever, you'll fold the fins flat and then you really have a problem. do it twice. a lot of guys find they've been hauling a quarter inch of grime around.

while you're back there, look at the fan clutch. the ones on these are mostly on/off, check that it actually engages when the engine's hot. the engine maker has the coolant and temp specs for your exact engine on cummins.com under the owner side, worth a look so you know where the warning lives.

Mesa here. everybody down here who lives on dirt roads or near farm fields has a dirty side radiator, and every July somebody's coach overheats on the climb out of Wickenburg. dale's right on the order. i'll add: cottonwood fluff. if you parked anywhere near a river in June it's in there.

adding this to the spring list. we spend January out on the dirt at Quartzsite and the La Posa south long term area is nothing but fine dust, the Forza must be packed. do you do this every year dale, or when the temps tell you

every spring if you winter in the desert, quartzsite. people who park on pavement can get away with every couple of years. look at it every oil change, which on these is once a year for most of you anyway, and write the climb temps down in the logbook on a hill you drive every year. that number is better than any light on the dash.