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Originally posted by MWrench:
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 transmission is indeed cooled by the radiator, but recall I transferred engine oil cooling to an external cooler with a fan. This should reduce the load on the radiator.

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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.

True enough, but the history is that the radiator is robust enough to handle the engine coolant and transmission.

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Any chance that the intercooler is leaking?

No chance at all. Ain't got no IC...

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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?

Engine performance is unchanged. Plenty of power, and EGT and boost are normal.

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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.

I clean the radiator with a mild detergent and a hose nozzle before long excursions. I don't use a pressure washer on anything.

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Ramblings, but all I can add for now.

That's what I'm looking for - I set this out as an exercise in thought for those forum members who aren't particularly mechanically inclined, as an exercise in thinking things through...

Just came back from the harbor, river has finally let us in and the coasties are opening the river for the recreational boaters. Cottonwood lint is thick. We may be several weeks, possibly a month behind those southeren locales you have been transiting. I remember cutting hay and loading up the radiator with pollen, dust and lint. What is the chance you have picked up such accumulations plus the occasional bug(s) down in the lower part of the lower 48?
I still like the IR thermometer gun, maybe it's just playing with the laser dot.

edit: Just posted, see you posted as I wrote. Ignore lint collecting radiator.
Get IR temp gun and have a good time.

Good reading on your "Test" so here's my suggestion: In my Regency Barth installed heat blankets on the exhaust manifolds, the turbo risers, and exhaust pipe all the way to the muffler. The build up of heat in the engine compartment is substantial under load and these blankets make a huge difference. If you have blankets check them closely - this requires removing the safety wire that holds them on and looking for burned through area on the inside. That's where I found my leaks in the exhaust risers. If you don't have such you might think about getting some. Mine were originally made by Advanced Thermal Products (http://www.atpwrap.com/) and after replacing them then engine compartment stays clean and cool. Without them the temp rises quickly under load and then subsides once back to cruising.

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I remember cutting hay and loading up the radiator with pollen, dust and lint. What is the chance you have picked up such accumulations plus the occasional bug(s) down in the lower part of the lower 48?

Dust/crud has never been a problem, and this is after many trips to the Nebraska Star Party. Dust does accumulate on the radiator, but its reserve capacity is so great that I've never noticed a performance hit.


My engine compartment is quite expansive and open compared to Regencies'. The only thermal blanket is where the A/C lines run somewhat close to the turbo hot side, only wrapping those lines.

The engine compartment stays relatively cool because, practically speaking, the engine almost sits out in the open.

Tomorrow, I go to Step #2, which I believe is the most likely cause. Someone here has mentioned it - what is that next step? .

even amongst the professional mechanics you will get different answers as to the next step...
and many more from us shadetrees, maybe a few leftfielders too, depending on how much was drank from the keg..

the KEG, the KEG - I need the KEG!!!

Otherwise, I'll have to use my judgement in proceeding...

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Originally posted by Rusty:
Tomorrow, I go to Step #2, which I believe is the most likely cause. Someone here has mentioned it - what is that next step? .

This is interesting Rusty. I am having a hard time not responding to this post.

Oh, wait, I just responded.

I like the post. This is turning out to be a great little excersize.

You haven't done anything like put a full width mudflap across the back under the bumper by chance? This is a good way to retain engine heat.

General Motors on their buses put a full width mudflap just behind the rear wheels. This also created a small vacumn pocket that pulled a lot of heat out of the engine compartment.

You could follow the path some shops do and just start replacing things until you get it right (and of course charge for all of it). The cause of the problem could be related to many of the suspected items listed above. No one here really knows, and we won't until you start narrowing down the likely culprits.

Step #2 was to have been to pull and test the thermostats; I drained 2 gals. coolant from the system, and then...see below!:

Q. How does one test thermostats?

However, I now believe the engine temp issue IS NOT cooling system related. I found something today, on which repairs are almost done, that I believe caused the problem.

What could it be?

You'd have to heat them in a controlled environment and observe their performance.

Something is generating more heat than it should? Is the turbo cooled? Bad temp sending unit?

Restricted air source (intake) or exhaust. ??!!

Testing thermostats - Put 'em in a pan of cold water with your wife's candy thermometer. Turn the stove on & watch the thermostats. When they start to open, take a reading on the candy thermometer. Let them fully open before you turn take 'em off the heat.

It ain't rocket science but its close enough for gummint work, & you can tell if they're working properly.

Easier to put the IR temp gun on the housing and watch for the opening. For $75 to $100 it is a tool too useful not to have in your tool kit.
http://www.grainger.com/Grainger/items/4XX07
Now that you have taken them out the "olroy method" is best.

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Originally posted by ccctimtation:
Easier to put the IR temp gun on the housing and watch for the opening.

Easier yet to put a couple of fingers on the housing. You will easily detect the temp rise when the thermostat opens. My thermostat has a couple of holes drilled in it, so the opening is not as dramatic, but is still detectable.

Admittedly, a Raytek is more accurate, but I can't find mine. And the few thermostat failures I have experienced or know about were dramatic enough that accuracy was not important.