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Old 07-20-2019, 04:25 PM   #21
Skoolie
 
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Quote:
Originally Posted by Warthog View Post
I'm amazed that no one on the thread has suggested adding an auxiliary electric fan (or more than on) to increase cooling air flow. These are typically mounted in FRONT of the radiator, as they need no mechanical connection to the engine.
I don't think a fan makes any difference at highway speeds. You're not going to get more airflow than what comes through the grill at 60 mph.

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Old 07-20-2019, 05:32 PM   #22
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First... I am kind'a busy and did not read every post. But....

A useful trick as old as the hills to combat overheating... is to turn the interior heater on full blast max temp. And open the windows, yes! That heat must come from somewhere -- yup, from the engine.

Next trick:

Millicent has traveled over 65,000 miles to events, including a dozen Burns, coming from Northern California.
Climbing over Donner (the Sierra Nevadas) is hecka grade. And from Wadsworth to Gerlach kind'a sneaks up on you elevation-wise -- not to be taken lightly heat-wise.

I used to drive trucks for a living, and they used to have a manual switch for turning the radiator-fan on.
And I installed one in Millicent.

When climbing, pulling more heat out of the engine sooner cannot hurt. And when approaching a stop, cooling the engine down a tad -- especially the turbo bearings -- might be a good thing.

BUT.... THE BIG BENEFIT of switching the fan on when approaching a climb... turned out to be for the automatic transmission.

Still, this involves the engine's thermostat. The thermostat is at the top and front of the engine -- the last "stop" for the water before the radiator.
In a nut-shell, the thermostat opens when the water around the cylinder head becomes hot.

More precisely, the thermostat maintains a good-and-hot-but-not-too-hot temperature in the engine, by continuously adjusting the flow of water from the engine to the radiator as needed.
THAT takes care of the engine. We can think of this as the upstairs part of the system.

Now, let's look downstairs.
Aha... this is where the transmission cooler lives.
Different brands and engines and whatnot may vary, but on Millicent... the transmission cooler is a fluid-to-fluid heat exchanger that looks like a box with four pipes attached.

Pipe 1 is hot transmission fluid from the transmission.
Pipe 2 is cool transmission fluid returning to the transmission.

Let me skip to Pipe 4 -- so we arrive at the important part last.
Pipe 4 is engine water returning to the engine cooling system (which may include the cabin heaters).

Now, Pipe 3.... Pipe 3 is cool water coming from the bottom of the radiator.
THIS is the stuff that cools the transmission.

Remember... the cooling of the ENGINE is regulated by the thermostat -- the upstairs portion of the system.

But cooling of the transmission... is regulated -- to the extent we can control -- by the TEMPERATURE OF THE WATER COMING FROM THE BOTTOM OF THE RADIATOR.

And the temperature of that water is affected by... by... by...? ...the air flowing thru the radiator. The fan.

So, I flip the fan on at the first sight of uphill terrain ahead. This maximizes the ability of the system to cool the transmission.

The proof is on the transmission temp gauge:
When pulling a heavy load up a long steep hill without the manual fan switch, the transmission temp would climb alarmingly.
When turning the fan on at the bottom of the climb... the gauge stays safely in the green.

On my second bus, which has the AT545 transmission, I simply hooked up the fan to run all the time, and she did the trip to the Playa also in the green.

I'm at 4:00 and C this year. Elliot's Bicycle Service & Piano Lounge. Please stop by!
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Old 07-22-2019, 04:56 AM   #23
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There’s lots of great advice here. I am a diesel mechanic who maintains a small fleet of medium duty trucks mostly powered by Cat engines and Allison transmissions. Let me just say that airflow is key. The very first thing to do is clean the radiator, a/c condenser and intercooler. If your bus is front engine, remove the grille, then very carefully, unbolt the a/c condenser and move it to the side. If the intercooler is mounted in front of the radiator, remove it. I like to spray degreaser on the radiator fins then use a pressure washer to blast out the crud. There will be an amazing amount of dirt in there. The pressure washer won’t hurt the fins as long as you spray straight on and don’t get too close. Now reassemble the whole mess and go for a test drive. If this doesn’t cure your cooling problem, the next thing to look at is the cooling fan. If the coolant temp is running over 210 or so, the cooling fan should be absolutely screaming. If you have a thermal fan clutch, it may have gone bad or need to be adjusted. That’s another fairly simple, but time consuming process.
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Old 07-22-2019, 12:28 PM   #24
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Hear, hear. One of the first things they told us in Chrysler's auto mechanic school in Detroit many years ago was to remove any sort of bug screen the customer had installed in front of the radiator.
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Old 07-22-2019, 01:06 PM   #25
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Lot's of great insight and experience here.

Since i mounted the transmission cooler in my bus no more constant up and down.

The engine itself was not getting hot. Radiator, thermostat, etc, ls just fine.

Once I removed the added heat of the transmission, the engine happy happy happy.
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Old 07-25-2019, 09:08 AM   #26
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Excellent post Elliot, hope you're enjoying the burn.

On a lot of school buses, the only cooler is the oil to water cooler. And since there is no temp gauge on the bottom of the radiator, most people have no idea how hot or cold the water going into the engine actually is. In an ideal system, I feel that your radiator fan should kick on based off of your lower hose temp. That temp alone will tell you if the ram air of driving is cooling enough or if the fan needs engaged to provide more.
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Old 07-26-2019, 12:27 AM   #27
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A sensor for the fan, at the bottom of the radiator, is a splendid idea. Even better, include a transmission temperature sensor in the circuit.

Still better.... What I have in mind might take some clever electronics, but could also be done with two sets of several (maybe three or four in each set) sensors of different ratings -- call them steps -- cleverly wired.

Imagine....

As the transmission temperature begins to climb and trips its first step, the bottom radiator hose begins to drop its temperature a step in anticipation of still higher transmission heat.

Then, if the second transmission sensor trips (a step hotter), the radiator-bottom drops TWO steps in anticipation....

And so on.

Be glad you don't live in my head. You would never sleep either. LOL

Regarding oil-to-water....
The Cummins 5.9 has an engine-oil to water heat-exchanger (oil cooler) inside the engine block on the right-hand side. (Ask me how I discovered this. )
Now I want a sensor or two there also, for gauges on the instrument panel. There is probably something to be learned there also.
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Old 07-26-2019, 08:05 AM   #28
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I installed a Horton E450 clutch on my red bus.. I use an automated controller on it .. on at 205 off at 198, but I also did what elliott did and have a manual switch so i can turn it on..



I use it when I go down long grades in low gear it creates resistance.. I also turn it on when I start up a grade so Im ahead of the game.. the IHC split rad / turbo cooler is barely capable of cooling going up and down hills in hot weather...



-Christopher
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Old 07-26-2019, 12:41 PM   #29
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Good point, Christopher. A fan this size does require a number of horsepower to spin at 2,000 or more RPM, yes, and every bit helps on downgrades.
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