It occurs to me that some of us are more experienced with engines, chasses, and house appliances, more than some other forum members.

So for your "pleasure", I submit a case study of a "situation" occurring on StaRV II. I have my troubleshooting agenda set, and have already a "suspect", but for those new to Mechanical Things I submit this situation for you to think through and post your analysis:

1. What you suspect could be the culprit?

2. What would you rule out?

3. What you would check first, second, and so forth, and why?

Situation:

Background: I got StaRV II 1/06. Shortly after getting it, I flushed the cooling system and installed DexCool 50-50% with distilled water. Dual 195°F thermostats and a Hi-Flow water pump were installed a few months later. The lower radiator hose was replaced with one from NAPA, although the one in place looked fine and felt limber. The NAPA hose has internal springs to prevent collapse at the bend, where the original was wire reinforced (bonded into the hose) its entire length.

In December '06, I installed a new engine, which also included the hi-flow pump and dual thermostats (180°F). The transmission still uses the radiator to cool it, but I installed a new external oil cooler with fan. New 50-50 DexCool was installed.

The tranny was rebuilt with heavy-duty components in April '08. A 2,200 mile round trip to NY produced none of the current symptoms, although ambient temps were typically 75-80°F.

Until recently, I could climb the 6%, 5-mile hill west of Chattanooga on I-29 with water temp never rising above 205°F, even in 95°F ambient. Accelerating onto the Interstates, the temp gage stayed on the minimum reading.

Current Issue: I first noticed temp going to 215°F (well within safe limits) climbing 8% hills in WV, with outside air at 82°F, but this persisted in 5-6% hills later. Accleration onto highways sees the temp gage climb also, sometimes approaching 205°F before I can back off having reached cruising speed. In all cases the temp is sluggish going back to the "normal" reading (compared to before), but it eventually does. Boost and EGT appear to respond normally.

So, what's happening here?

Rusty, is the fan mechanical, electric, hydraulic?
My first check would be to remove the radiator cap when the engine is cool and see if I could determine how much water flow I had. If I had good flow I would look for any kind of air blockage across the radiator. It sounds like it is running hotter than usual but not HOT.Is that right.
Nick

The fan is belt-driven, connected as it is to the water pump shaft. I got a bit of mud onto the back of StaRV II when attempting to pull it out of mud in Ohio, but there's very little on the radiator fins.

Well, my first check would be the radiator cap.
and or the lower radiator hose in unison. why?..
well being that you changed the lower hose with a
spring only in the bend and not fully reinforced as the old one was, and even though you have hi flow water pumps you still need to maintain a certain amount of pressure in the coolant system.
water flow and water pressure are two different things. could it be as you drive up a grade, the water pump pushes the water but not enough pressure is there causing a collapse of the lower hose momentarily, thus choking water flow through the system?? maybe..maybe not...or maybe the thermostats are too low of temps 180 vs 195?? or did the addition of the oil cooler with electric fan cause an offset of airflow within the engine compartment??..maybe....but the cheapest and first thing i would do is buy a new radiator cap,
with the proper pressure., it's the easiest thing to check....just a thought...or guess.lol..

ZIM

well i wouldnt clean the radiator with a pressure washer bent fins

I'd buy that Beaver and use this as a trade-in, or sell it to me.

My first guess is a dirty radiator. The rear ones can pick up a lot of dirt. Solution is to get a couple of spray cans of spray and wash (laundry) and thourly soak your radiator and then rinse it out.

Second guess might by transmission if it is slipping or the torque converter is not locking up.

I will eliminate the fan as at cruise speed it may not even be doing anything. The drag on the rear cap may be enough to pull the air thru the radiator.

And finally I have to assume you checked the radiator to make sure it was full. I was heating slightly and discovered I was down a little on anti-freeze.

I first checked the lower hose - a collapsing hose could produce the symptoms - and relearned that it's wire-reinforced its entire length. So that's ruled out.

Why did I check the lower hose first? Logic. It's the easiest thing to check.

BTW, there are no leaks in the system.

As Tim mentioned, residue from the old engine is ruled out, as the system was flushed, rinsed with distilled water, then six months later, flushed and rinsed again.

So, what to check next?

Maybe everythings OK, and the gauge and/or sender isn't telling the truth anymore?

Always worth suspecting! However, the gauge returns to normal when cruise speed has been established for awhile, or when idling for a time.

Anyone: What's my next step?

How bout since its been 2 year since ya put antifreeze in,how bout checking the strength of the antifreeze?...another guess...lol..

ZIM

A rational consideration - actually, the AF is only 20 months old (23K miles), and is DexCool, said to be good for 5 yrs./50,000 mi.

If you know that you have reasonable coolant flow and pressure, and a good radiator, I'd take a hard look at the thermostats. Is the engine still performing as expected? A problematic engine could be reflected in higher temps under load or even the trans.

I am wrestling with the same problem even though different engine transmission etc.

Couple of things:

As the radiator does in fact do some of the transmission cooling duties, there will be a "heat soak" issue, the heat as built during a climb will have to be dissipated and that will contribute to a longer then normal cool down period.

The only air thru the radiator will be by fan action, there is NO ram air or ducting effect in a diesel pusher. I have done extensive studies on mine with yarn tuffs and can directly see them with a video camera, If I lift and let idle at speed the tuffs show no air flow. Having said that, a major cause IMHO for cooling issues is the collection of hot air from in and around the engine bay and that hot air being blown thru a radiator, air from just above the road will be much hotter then air 3-5 feet above the road surface. Probably most of the air drawn into the engine compartment is coming off the road.

Any chance that the intercooler is leaking?

As these condition seem to be new, something is changing, Does the engine seem to have the same power and ability to climb these grades at the same speed as before?

Rear radiators tend to get crudded up and maybe you have air blockage. As has been stated, don't ever use a pressure washer to clean a radiator, I used a city water pressure and one of those small "fire nozzles" and succeeded in bending some fins over and that caused a leak ($1300 later---another story) I usually wash out the radiator after each trip but I have an additional problem that I have the turbo intercooler first, then the trans cooler second and then the radiator, so is it impossible to clean all of the stuff out of all of the fins that would block the air flow.

Ramblings, but all I can add for now.