Prior to current long road trip, I had auto repair shop flush and replace the engine coolant in my camper van (Class B motorhome) built on a 1990 Dodge B250 with 5.2L engine. Engine has 147,000 hours.

Temperature gauge has "C" line (low), "H" line (high), and four intermediate lines. No degree numbers.

On moderate up and down grades, I can hold 65 MPH and the temperature gauge varies from the first intermediate indicator line to the second intermediate indicator line.

When I am going up a long 6% uphill grade (mountain pass, etc.), I disable the Overdrive and push the gas pedal down to maintain as much speed as possible, but van slows down to about 45 MPH. She is pretty heavily loaded, probably near the GVWR. The temperature gauge indicator rises to between the 3rd and 4th lines. It is getting hot in there. If I don't let up on the gas a little, I think the temperature would keep rising but I don't want to chance overheating.

When I'm going down the mountain grade, not needing any gas pedal, the temperature drops to just below the first intermediate indicator line (just above the "C" line).

What could be the problem(s)?

Thanks,
Mike

 

It doesn't sound like a problem, just normal operation.

If the temp is bothering you, try a water wetter.

220 temps are not uncommon when really ******* a van.

 

It is not as if a radiator flush restores 100% performance back to the cooling system. A flush requirement is more a sign of neglected normal maintenance.

 

It's either a sticky thermostat or a weak radiator. To fix the problem you'll be replacing one or both.

 

a nascar"3 row" radiator is in order