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Old 01-03-2017, 09:56 AM   #1
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Viscous fan clutch? DT466E 3800 dognose

I was coming back from New Year's camping trip yesterday and noticed the coolant temp starting to climb higher than usual. (I have a scanguage connected so at least I'm getting an accurate number) I started to get a little worried as it got closer to 220 and I could not hear the fan engage like it normally does... I slowed down a bit, took back roads and was able to keep it below 220 and make it home.

Here's the question: are those things notorious for just going out? Is there anything I can adjust/fix on it or does it just need to be replaced.

Second question - is the replacement of it fairly easy?

Thanks in Advance!!

John
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Old 01-03-2017, 10:08 AM   #2
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IIRC
when cold you can turn it by hand but "stiff".
Fan and the hub where blades are attached, not the part that the belt rides in.
Over time the shaft seal leaks and when the fluid leaks out it gets easy to turn fan by hand. Virtually no effort needed to move it.

I have same engine and chassis so I can look later tonight to see how difficult.
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Old 01-03-2017, 10:36 AM   #3
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just went out and checked - engine cold - fan turns pretty easily, doesn't have too much resistance on it. Also looks like there is some crud around the shaft like a small leak. I bet the clutch is shot.

Thanks!

John
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Old 01-03-2017, 02:47 PM   #4
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Year: 1991
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Chassis: International 3800
Engine: DTA360 / MT643
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viscous fan clutches... theres a few "issues" on internationals with them..

1. yes they can "just quit".. or they seem to take longer and longer to engage over time. so the engine creeps hotter..

2. they measure the AIR temperature from the radiator and NOT the coolant temperature.. so if you have any type of coolant flow issue or clogged radiator fins. the first thing that will happen is the fan wont run because the air temperature from the radiator is not high enough to engage it..

3. IHC SPlit radiator design doesnt help things... typically your turbo air is cooler than radiator air which keeps the fan clutch more towards disengage... esp when its cooler outside.. if your rad fins are clogged but your turbo fins are not.. even worse..

4. if your clutch has an exposed temperature coil (which many do) that coil cazn get covered / caked in dirt over the years. insulating it from the heat - raising engagement temperatures...

How I fixed mine.

1. I took the fan off and pulled the shroud back and cleaned my radiator fins.. (INSIDE OUT... the dirt is brought in from the front so blowit back out the front..).. I used high pressure shop air nozzle and then a garden hose and then shop air.. I didnt want to bend the fins or risk it with power washer....

2. I replaced the clutch with a part from kit-masters.. call your IHC dealer, give them the VIN, tell them you are looking for fan clutch.. they will give you a price.. ask the OEM part number, and then kit-masters can cross reference the IHC OEM part number..

3. what you will get is (hopefully) a thermal viscous clutch with an adjustable coil. (when you call kit-masters go through support and ask them what temperature its set at from their factory)... I reset the temperature down to 150 (2 notches from the factory 170).. on my DT-360.. now my fan engages fully when my coolant temp is close to that 185 point.. ive seen it go to 190 when it was a cooler day and I was pulling a hill... your mileage may vary with the DT-466..

4. I put the clutch on not by disassembling everything under the hood like the book says but by separating the fan from the clutch before unbolting the clutch.. on the DT-360 it was 4 bolts for the clutch to engine.., on the T-444E it uses a fan clutch wrench (I have the wrench set for those.. not sure what the 466 has)..

I slipped the clutch out, replaced it and put it back together without having to take anything else apart.. on my T-444E I had to remove the serp belt for a little clearance..


hope this helps

I have 2 happy cool-running busses after replacing those clutches on both..

-Christopher
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Old 01-03-2017, 02:52 PM   #5
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The guy I got my bus from said he noticed it was running warmer than usual. He welded the fan solid & has never ran warm since.

Just a option.
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Old 01-03-2017, 03:51 PM   #6
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Thank you, Christopher!! I will give it a clean first and see what that does and keep you posted!

BigDavid - That's a thought too! Probably lose some precious MPG's though... ;)


John
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Old 01-03-2017, 06:28 PM   #7
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Quote:
Originally Posted by BigDavid View Post
The guy I got my bus from said he noticed it was running warmer than usual. He welded the fan solid & has never ran warm since.

Just a option.
Thank you because as i was reading this i began to wonder why have a clutch at all?
I think i recall that engines perform better if brought up to temp, which would be tricky in winter but at least does not risk damage in summer.

Good to know an alternative exists.
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Old 01-03-2017, 07:44 PM   #8
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As far as mpg goes, I calculated I got 11.89 coming back from Mississippi to Georgia. I need to put a few tanks in to really get a accurate number.
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Old 01-03-2017, 09:03 PM   #9
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welding the fan clutch on a newer bus can be done however some implications.. on a big engine not likely to make a huge deal in fuel economy.. but the fan blades generally arent balanced for the full RPM of the engine... even when a fan clutch is fully engaged the blade is not spinning at the full RPM of the pulley.. so the bearing on whatever its attached is likely life-shortened..

your fan blade may also not be rated at the full engine RPM which means it could fly apart... that will usually destroy the radiator, the shroud, and often before you can shut down the engine it will bus the shafty or vibrate so hard it will shear the bolts..

secondly is even with a thermostat these biusses have a fair amount of coolant bleed to the radiator to keep the system from trapping air. so in cold weather your engine will have trouble making temperature esp if you idle at all..( alas why school busses have the pretty covers over the grill in winter.. ) or are like my DEV which has a fancy temperature cointrolled louver shutter that closes in winter.. (that I forgot to plug in the wire and so did me no good on my last trip to the great north)..


the belt - if your belt becomes even the slightest bit loose it will slip and break...

my suggestion? fix the clutch or buy a fan designed to be a straight run fan.. (yes you can buy fan blades that are designed to run at full engine speed for long periods of time..)
-Christopher
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Old 01-03-2017, 09:42 PM   #10
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Dump the hydraulics and go electric.
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