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Old 07-20-2022, 10:46 AM   #1
Mini-Skoolie
 
Join Date: May 2021
Location: WA
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Year: 1994
Coachwork: AmTran
Chassis: International 3800
Engine: International DT408
DT408 Overheating diagnosis

Hey all! I have a 94 AmTran Genesis with a mechanical DT408 (necked down DT466), MT643, in a flat nose 36' body.

I'm posting just to ask if anyone can point me in a direction to diagnosing some overheating issues I'm having (or perceived). I'm no stranger to vehicle repair and love to DIY, but the lack of body/motor support/forums of similar problems has left me lost.

Fan/clutch/rad pic from the rear: https://imgur.com/a/pddPsyY

Only on hot days in the summer climbing hills will my gauge climb to dangerous numbers, my understanding is to not run over 220 so thereabouts is where I pull over. When I do, I notice little airflow which makes me think fan clutch, and it takes a significant amount of time to cool down to push up the hill a bit higher (10min+). I figured maybe there was bad airflow through the stupid split rad/IC, so I've blasted it with water to help clear out any debris/bugs collected. The radiator used to have a small crack which I brazed and JB Welded over the braze for good measure (my first time brazing...). It seems to be holding well, no leaks, but it could point to other rad issues. My understanding is if the system can't build pressure, the coolant won't flow, is that right?

It's not like I'm climbing mountain passes with a loaded bus, I'm talking a couple miles at 5% grade in an empty, stripped bus.

Is there any good way to diagnose the problem that doesn't involve throwing parts at it?

Fan/clutch/rad pic from the rear: https://imgur.com/a/pddPsyY

Are there any "quick fixes" such as forcing the clutch to always be engaged for the short term?

Being a flat nose, does that mean significant pre-work to even get to the fan clutch? Rad/bumper have to be removed?

Does anyone have any suggestions on repair manuals that would be more specific to my bus body? I don't even know where to start to take things apart other than start turning bolts and hope for the best!

Thank you in advance so much, any comments welcome.

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Old 07-23-2022, 01:05 PM   #2
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reach out to EWO1 on here i think he may be your best shot for manuals.
have you added an auxilliary trans cooler?
if not even if the fan clutch is working would help.
do you know that your thermostat is opening all the way.
many of my heavy tow/haul vehicles i have went out of the way to pull the thermostat for the summer months and put it back in on some of them for the winter time.
fan clutch , thermostat, and tranny cooler and or even changing to a full rad. after the tranny cooler.
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Old 07-23-2022, 01:31 PM   #3
Mini-Skoolie
 
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Thanks for the tips Jolly Roger!

No I've not done any engine/drivetrain modifications. Do you ask because it would add cooling to the engine rad? Trans temps have been solidly low - according to the dummy gauge.

I just bought a replacement thermostat and rad cap I am going to install and test today.
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Old 07-23-2022, 02:28 PM   #4
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separating the tranny and rad will make a big difference even keeping the split radiator. and a separate tranny cooler
i dont really trust any dash gauges but i own things from the 70's and up to 21.
i love everything until y2k/2000.
what the hell were they thinking?
oh yeah emissions ****?
we are still there?
i will keep vehicles that dont require computers.
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Old 07-23-2022, 09:10 PM   #5
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an experiment...

move the hose from the windshield washer bottle so that you can spray water down the front of the radiator..... You are going to use the spray to help take heat out of the cooling system. try this on the road on one of those hills that puts a little stress on the cooling system.

If you see significant drop in temperatures.... I would have to say you are or have lost air flow. That means fan clutch and or junk in the cooling fins and or loss of cooling fins.

I have seen cases from road salt areas where all the little copper cooling fins are just gone... only the tubes left, no fins.

adding transmission oil cooler.... I think I would make the transmission oil go through the add on cooler first, then through engine coolant heat exchanger, then return to the transmission. Why? In very cold weather you can add some heat into the transmission oil. Engine oil, transmission oil, hydraulic oils work much better 120 degrees to 200 degrees. Oil too cold makes life kinda rough on the pumps. Too hot can break the oil down so that it does not lubricate like it needs to. Too cold and engine oil can have a difficult time getting to all the places it needs to.

I invite others to correct me if you think this is not well advised.

william
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Old 07-23-2022, 10:30 PM   #6
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the MT643 doesnt make near the heat the AT545 does.. the fan should definitely be ripping fast at 215-220.. kit-masters will have the clutch for that..



dont bolt the fan clutch to full-time.. . even fully engaged, fan clutches have some degree of slip and are designed to hit a maximum speed regulated by centrifigul force.. if you bolt the clutch you can over-speed the fan blade.. and yes ive had a fan fly apaert before on a car and its not a fun experience.., it did FAR MORE damage than just the blade ...
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Old 07-24-2022, 05:29 PM   #7
Mini-Skoolie
 
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Thank you everyone for all the advice so far!

I got the engine hot and did some testing based on various advice I've gotten:

Thermostat block temp:


Top of rad max temp:


Rad outlet temp (145):


Seemed like there was quite a lot of air moving through the rad, enough to suck a piece of paper against the winter louvers firmly. I still wouldn't say it was "roaring" like an airplane taking off though, but maybe I'm just deaf.

Turned it off hot (~195°) and moved the fan blades. I could push them with effort and they didn't freewheel spin at all no matter how hard I tried.

I replaced the radiator cap as the old one was who knows how old, and said "replace when changing coolant"

I haven't had a chance to test if I'm still Overheating as I couldn't get it hot enough stationary at 2k rpm, but based on all the troubleshooting info all the wonderful skoolie peeps have imparted on me, the only logical idea I can come up with is reduced flow, either the thermostat not opening all the way, or maybe water pump not pumping as much as it should.

Ideas/thoughts?
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Old 07-24-2022, 06:09 PM   #8
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Just by what you have posted, id say the fan is slipping. I couldn't open your pictures. Does this have an air operated fan clutch? If so, you could unplug the solenoid that feeds air to the clutch fan and see if it turns faster. Mine was worn out and constantly slipping. Same symptoms you are having. I'm with Cadillackid in that the fan should be ripping at 220 degrees.and moving some serious air
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Old 07-24-2022, 06:15 PM   #9
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Quote:
Originally Posted by SKOOL-E-O View Post
Just by what you have posted, id say the fan is slipping. I couldn't open your pictures. Does this have an air operated fan clutch? If so, you could unplug the solenoid that feeds air to the clutch fan and see if it turns faster. Mine was worn out and constantly slipping. Same symptoms you are having. I'm with Cadillackid in that the fan should be ripping at 220 degrees.and moving some serious air



viscous fan clutches never engage to a solid engagement. . and the minute you shut the engine off the fluid moves around so trying to judge resistance in this manner isnrt a good test... in my case i located an electronic remote sensor in the air stream on the rad side of the split and watched my air temp in the cab... knowing the clutch was set factory at 195-200 AIR TEMP (according to IH).. and noting i was pushing 210 degree air and the fan was still spinning about 300-600 RPM i new I had an issue..


unless the clutch has visibly leaked its fluid out (you'll see it).. then they almost always still work at minimum speed which at idle will keep the engine more than cool... even on a high idle as its stil a No-load run.. when you are getting hot your engine load fasctor is probably close to or at 100%.. at idle even with A/C its usually at like 18-23%
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Old 07-24-2022, 07:30 PM   #10
Mini-Skoolie
 
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Quote:
Originally Posted by SKOOL-E-O View Post
Just by what you have posted, id say the fan is slipping. I couldn't open your pictures. Does this have an air operated fan clutch?
No, it looks like a viscous clutch to me with no electrical or air connections to it, but I'm not 100% confident there isn't some alternative routing for air I don't see.
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Old 07-24-2022, 07:40 PM   #11
Mini-Skoolie
 
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Quote:
Originally Posted by cadillackid View Post
viscous fan clutches never engage to a solid engagement. . and the minute you shut the engine off the fluid moves around so trying to judge resistance in this manner isnrt a good test...
Ah dang okay, I was going off a suggestion from another forum there.

Quote:
Originally Posted by cadillackid View Post
in my case i located an electronic remote sensor in the air stream on the rad side of the split and watched my air temp in the cab... knowing the clutch was set factory at 195-200 AIR TEMP (according to IH).. and noting i was pushing 210 degree air and the fan was still spinning about 300-600 RPM i new I had an issue..
So like one of those little outdoor temp sensors with the wire and probe? And you put the probe between radiator and clutch? I like this idea!

Quote:
Originally Posted by cadillackid View Post
unless the clutch has visibly leaked its fluid out (you'll see it).. then they almost always still work at minimum speed which at idle will keep the engine more than cool... even on a high idle as its stil a No-load run.. when you are getting hot your engine load fasctor is probably close to or at 100%.. at idle even with A/C its usually at like 18-23%
That's good to know, I figured parked wasn't enough load to hit overheating. Do you have any advice on knowing what rpm the fan is spinning? It sure looked like it was ripping and lots of wind, but didn't sound like crazy over the sound of the engine.
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Old 07-24-2022, 09:39 PM   #12
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Quote:
Originally Posted by Phreqq View Post
It sure looked like it was ripping and lots of wind, but didn't sound like crazy over the sound of the engine.
When it comes on you shouldn't have any doubt about whether it came on or not.
Around two years ago I had a similar issue with a Dt466E and a 545. I replaced everything I could related to the engine cooling. Post mortem on the radiator showed clogged tubes which didn't allow for proper coolant flow when the trans temp was factored in. Except for a leak in the drivers heater it's been fine.
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Old 07-25-2022, 07:52 AM   #13
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Quote:
Originally Posted by Phreqq View Post
Ah dang okay, I was going off a suggestion from another forum there.



So like one of those little outdoor temp sensors with the wire and probe? And you put the probe between radiator and clutch? I like this idea!



That's good to know, I figured parked wasn't enough load to hit overheating. Do you have any advice on knowing what rpm the fan is spinning? It sure looked like it was ripping and lots of wind, but didn't sound like crazy over the sound of the engine.

often on a Working fan clutch they will go into full engagement mode when you first start the vehicle.. theres no mistaking it.. if you have the hood open and run the RPM up to 2000 .. you will definitely know the fan is there!! mine runs for the first minute or so i start the engine.. then it quiets off as the fan blade goes down to its minimum speed.. I dont know if i can take a video of the fan roar without windo noise i nthe mike or not.. i can try..
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Old 07-25-2022, 08:33 AM   #14
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The difference in air movement between engaged and not is substantial. Like CK said, it will be engaged for 10-30 seconds at startup, so start it up, rev it up to 2k rpm, and if the fan "noise" doesn't change after running a few minutes, you can count on your clutch very likely being bad.

Also, viscous will never fully lock, it will also never fully unlock. Something like 25%-95% applied, that window depending on the duty cycle of the clutch. A lot of viscous clutches I see are bad, and people don't know it, because going down the road unloaded on flat highway doesn't require any fan. The ram air from travel is enough cooling.

If you can't see in the radiator to look at tube condition, remove the upper hose and use a bore scope. Being 20+ years old there's a good chance you have an issue, and those split radiator/cac units are the worst when it comes to overheating.
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Old 07-25-2022, 08:36 AM   #15
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IMO, you can't test a viscous clutch with the engine off. It has to be running. I reference this video a lot to people asking how to test it, as it's short and to the point.

Even if the clutch is "disengaged" you shouldn't be able to stop the fan.
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Old 07-25-2022, 10:52 AM   #16
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Quote:
Originally Posted by Jolly Roger bus 223 View Post
reach out to EWO1 on here i think he may be your best shot for manuals.
have you added an auxilliary trans cooler?
if not even if the fan clutch is working would help.
do you know that your thermostat is opening all the way.
many of my heavy tow/haul vehicles i have went out of the way to pull the thermostat for the summer months and put it back in on some of them for the winter time.
fan clutch , thermostat, and tranny cooler and or even changing to a full rad. after the tranny cooler.
I found this service manual.. I hope it contains enough info for you to get the job done!

SERVICE MANUAL SECTION - S12043 - 2012
RADIATOR / COOLING SYSTEM SERVICE MANUAL
Model: RE Bus with Side-Mounted Cooling Package
Attached Files
File Type: pdf 01 - (2012) Radiator & Cooling System (S12043).pdf (1.21 MB, 3 views)
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