DT466 and MT643 Questions

[bigskypc50]

Toke my bus out for a drive the other day (second time in 6 months I have had on the interstate) on a 160 mile round trip to home depot. Just a test run and also to keep everything lubed up and running well from sitting around.

Also got the bus weighed at the local cat scale, steer is 10180 and drive is 13480 for a total of 23660 holly crap that's a big bus!

Overall it did very well, but I have few questions.

1: Is this normal shifting for a MT-643?
https://goo.gl/photos/EXRJeGBYsQSAmfAM8

2:How hot is too hot for a DT466? On flat roads and normal driving the bus is doing 60MPH at 2200RPM and won't budge from 180 degrees, but on long hills like a 6% grade for quite a few miles almost pedal to the floor doing 45MPH, I will see the temp gauge start to go up, On the dash when the needle was half way over "2" in 210 I was worried, next hill it was between the 2 and 1 in "210" I slowed down and downshifted into "3" and it held there until the top of the hill, the bus will very quickly got rid of the heat and settle back down to 180. The temp gauge is bit confusing I see the line for 210 is in the 0, I assume anything between the 180 line and 210 line is normal? What's the proper way to baby the DT466 up hills?

3. I noticed the voltage gauge is jumping around it will fall to just above 12 volts and bounce right back up to 14V, it will do that maybe once or twice a min I hope it's not the Alt the service records say it was already replaced to the tune of 800 bucks. It's 175Amp it says.

[cadillackid]

if you have a Bosch type alternator, it is designed to run in SI or single wire mode.. in single wire mode, it has no way to sense true system voltage, so from what I understand, the alternator shuts off for an instant every so often to "check" system voltage.. and then turns back on.. this has been doing this on my DEV bus ever since i got it and I did lose an alternator, put the same type on and it does the same. when I tested it with a Sense wire this operation didnt occur..

when your bus was nearing 210 did you hear the roar of an engine fan? if not, id begin to suspect the fan clutch could be bad...

-Christopher

[EastCoastCB]

Sounds normal to me. My bus has a 466/643 and yours sounds like it behaves the same as mine.
I bought it in KY. On the way home it stayed just under 180 on the gauge.
We hit monteagle in TN (6% grade) and the temp went up into the low 200 range.
Pulled over at the top and let it idle for twenty mins and it stayed at 180 the entire way home to FL.

[bigskypc50]

Thanks guys for the feedback super helpful, I don't remember the roar of the fan on the long runs up hill (but there is a lot of road noise ect), but I do remember the roar of the fan when I pulled off the interstate got weighted and went to get back on, I could hear that fan. It seems total random when kicks in or not. I honestly don't hear it that much.

Glad to know everything is normal, as most of us never drove a school bus in my life and have not ridden on one for 20 years.

[cadillackid]

the fan is somewhat "random" unless you are lucky and have an electronic fan clutch (mosrt dont), there is a little spring coil in the center of the fan clutch.. it measures the temoperature of the air coming from the radiator.. so the coolant heats up and warms the air that the fan is in contact with which will rotate that spring xoil and cause the fan to spin.. the fan spins, the air cools, and the clutch disengages.. at road speed its less likelyt for the fan to engage although when working correctly, it will when thinks get hot enough..

if you shut the bus off for awhile and restart it, the clutch almost always engages for the first couple minutes to distribute that fluid inside the clutch.. it also tends to run more at lower speeds as there is less air coming into the radiator so thigns are hotter..

its not really random but it kind of seems like that.
-Christopher

[Busmanmoab]

gotta chime in on this one . Im having the same issue. On my 9 liter i replaced the spendy fan clutch with a new one. So when you are driving and the temp. hits 190-200 you should hear a notable difference in the fan noise ( very loud like a train) until the temp goes back down. this is the visco clutch engaging the fan i e spinning faster. So my dt4666 with the same tranny when i pulled hills last week in hot weather goes silent not good! At International they call for all old dt466 to be upgraded (1200$ in parts) to a Horten electronic fan clutch, to spendy. So Brent (my parts guy at IH ) went in the back and found something that fits ( only $500 :[ ) , Im gonna put it in today or tomorrow I will let you know how it works. P S yesterday 103, today102 degrees perfect weather to test the cooling system! And if anyone needs to know the joyus removal procedure let me know (get ready for sweat and bloody knuckles) If it works ill show you the part number and some pics, if not i will hang my head in shame and sell the dog to make back the $500 !

[Tango]

Have to admit, I like Chris's fix. Drill a hole and bolt that sucker so it turns full time. Like the price too.

[cadillackid]

I don't advocate it as a perm fix but if it means I can stay in the saddle with my AC on by god the drill is comin out
Christopher

[cadillackid]

Originally Posted by Busmanmoab

gotta chime in on this one . Im having the same issue. On my 9 liter i replaced the spendy fan clutch with a new one. So when you are driving and the temp. hits 190-200 you should hear a notable difference in the fan noise ( very loud like a train) until the temp goes back down. this is the visco clutch engaging the fan i e spinning faster. So my dt4666 with the same tranny when i pulled hills last week in hot weather goes silent not good! At International they call for all old dt466 to be upgraded (1200$ in parts) to a Horten electronic fan clutch, to spendy. So Brent (my parts guy at IH ) went in the back and found something that fits ( only $500 :[ ) , Im gonna put it in today or tomorrow I will let you know how it works. P S yesterday 103, today102 degrees perfect weather to test the cooling system! And if anyone needs to know the joyus removal procedure let me know (get ready for sweat and bloody knuckles) If it works ill show you the part number and some pics, if not i will hang my head in shame and sell the dog to make back the $500 !

I bought my horton EC-450 fan clutch on fleabay new in the box for about 250.. then used a dakota digital fan contrioller.. now I have full control over the fan.. either first by coolant temp or I can click the manual button and spin it all the time if I choose..
I have thread here where i detailed the install
-Christopher

[chev49]

on the long interstate hills such as eastern oregon, or past salt lake, when my cat engine gets up to about 200, I just slow down a little. I have never stopped to let the thing cool off. My detroits ran same temp range.

[cadillackid]

here is where I started in my thread about my Horton EC-450 upgrade.. well worth it!

http://www.skoolie.net/forums/f18/go...-15124-20.html

[Busmanmoab]

Originally Posted by cadillackid

I bought my horton EC-450 fan clutch on fleabay new in the box for about 250.. then used a dakota digital fan contrioller.. now I have full control over the fan.. either first by coolant temp or I can click the manual button and spin it all the time if I choose..
I have thread here where i detailed the install
-Christopher

wow what a great deal ! way to go ! I didn't see this old post of yours i wish i did i would have gone this route !

[cadillackid]

Originally Posted by Busmanmoab

wow what a great deal ! way to go ! I didn't see this old post of yours i wish i did i would have gone this route !

it definitely helped... I still had a temp of 216 or so when I was running at 70 MPH in 103 degree F florida weather.. cant wait to see how it acts now that I'll have the locked and overdrive transmission.
-Christopher

[Robin97396]

Having your radiator cleaned thourally should have helped a lot too. In combinatuion with the lockup transmission I'd guess you just ended your overheating issues.

[cadillackid]

Originally Posted by Robin97396

Having your radiator cleaned thourally should have helped a lot too. In combinatuion with the lockup transmission I'd guess you just ended your overheating issues.

doing my cooling system upgrades definitely made a huge difference.. of course part of that was clean the rad.. ive also done some reading on school bus fleet and a trucker board that the aftermarket replacement radiators everyone uses for these 444E's dont work as good as the real navistar part.. not sure if there are differences in the cores, maybe the materials its made from? but of course 95% of the time people install the aftermarket (which mine is) because its cheaper..

my AT545 trans never ran hot.. everyone says AT545's make tons of heat so if mine wasnt running hot.. then that heat was going into my radiator cooling loops...
-Christopher

[Robin97396]

I've taken my 545 over the mountains where I consider it to be a real test. Long steep pulls in first and second. I was actually pleasantly surprised at the way it descends steep hills, especially after all the smack talk about how they freewheel.

So far as I can tell my radiator is good. My fan is another question mark, and it's not exactly accessible anyway. It does come on sometimes, so I'm going to leave it at that until there's a problem.

I'm still hoping to see you put a 1545 in your other bus. How cool is that? A 545 with a locker and PTO. Think about putting a generator motor on the PTO.

[Versatile]

Originally Posted by Tango

Have to admit, I like Chris's fix. Drill a hole and bolt that sucker so it turns full time. Like the price too.

I missed that part. Where is it at? thanks

[cadillackid]

Originally Posted by Robin97396

I've taken my 545 over the mountains where I consider it to be a real test. Long steep pulls in first and second. I was actually pleasantly surprised at the way it descends steep hills, especially after all the smack talk about how they freewheel.

So far as I can tell my radiator is good. My fan is another question mark, and it's not exactly accessible anyway. It does come on sometimes, so I'm going to leave it at that until there's a problem.

I'm still hoping to see you put a 1545 in your other bus. How cool is that? A 545 with a locker and PTO. Think about putting a generator motor on the PTO.

you have a full radiator and not a half split.. the half split radiators used on a lot of navistars are the issue as they have such small capacity.. .. there are 2 factors at play when a cooling system is operating..

1. the cooling system's ability to remove heat from the engine into the coolant..

2. the ability of the cooling system to dissipate the heat into the surroundings..

its entirely possible that you cooling system can remove more heat from the engine than it can dissipate to the surroundings.. esp if climbing a hill or such..

if you have a LARGE capacity cooling system, then the coolant can store that heat .. in the form your temp gauge slowly rises.. because you are putting more heat into the cooling system than it can release...

a tempoarary condition like climbing ah ill, a proper cooling system will be able to store enough heat in the coolant that once you are off the max power your radiator is capable of dissipating as much or more heat than is being removed from the engine..

with the small navistar radiators, you not only reduce the capacity of the heat that can be dissipated.. you also reduce the amount of coolant, and therefore the amount of heat storage that can take place..

running with your heater valves turned open puts another 5 gallons of coolant in the mix.. ie - Heat storage capacity.. even with the vents closed and the fans off (you asrent dissipating much heat this way or making your bus too hot inside).. you now have nore ability to store heat for that long hill pull before you reach a critical temperature point..

-Christopher

[Robin97396]

I thought something broke the first time I heard my cooling fan come on. It blows so hard the doghouse lid actually lifts a little bit and hot air blows on my throttle foot.

I watch my rpm's rather than flooring it. My heat gage actually gets to the top side of the temp range just going up the hills to get back home, but it doesn't ever seem to overheat.

I do still have the heater hoses running to where the rear heater used to be, but mine run under the floor. I consider that to be spare hose if I need it.

I don't like learning to trust a new vehicle. This one seems excellent but I always have a fear of getting broke down somewhere.

It's been getting so hot I think it's time to take a trip.

[bigskypc50]

My bus had a new radiator installed in 2006 there is a sticker on it that says the date, the service records just simply say "Massive Leak" & "New Radiator" with no date or milage. Also I don't know if all bus's have them but right in front of the radiator are air powered shutters that totally close off all air flow to the radiator. All I know its they close after a I start the bus and are open when I shut it down when it's warmed up.

How can I tell if my RAD is OEM and of the split or full? I can tell you it has a sight glass thats up from top center and a petcock at the bottom. I still can't figure out how to add coolant if it every needs it, sure there is the little bottle under the wire nest service door but I hope it has a rad cap? Is it behind the genesis plate thing.