1997 IH 4700 DT466 Allison AT500 question...

I have a 1997 IH4700 with a DT466 and an Allison AT500 automatic transmission. (wish it were a spicer 7, personally, but I got a good deal on it.)

Here's a refreshing picture of it, on this 100 degree day...



So, taking a 120 bushel load(should be nothing for a dump that can legally carry 13,500 lbs of payload) to the elevator today, it started playing tricks. Now, I know it is hot outside, but, it shouldn't do this. When going uphill on the highway at 55 mph, it started to blow blue smoke pretty heavily out the exhaust pipe. Then, within a few minutes, the tempurature gauge hit 230 and all the warning lights came on for running hot. It is full of coolant. It has 107,000 original miles on it. The one thing it does have is a new muffler that was put on it by a shop in December. I'm wondering if maybe the muffler is restricting teh exhaust flow too much and causing the turbo to get too hot, which is allowing teh seals to leak. Once I go below 55 mph for a distance(say 45 mph) it will quit doing this. I don't have a pyrometer on the exhaust. I'm guessing that it will say I'm running really hot.

Does anyone have any experience with one of these engines in a truck? I fooled with them in tractors, but never in a truck. The transmission really makes that thing rev high almost all the time. running 65 mph it is at 2700 rpm nearly. Coming back, unloaded, it was running cool and no smoke, but I was careful not to go a click above 55 and keep my foot out of the gas tank going up any hills. There is one 7% grade I climb empty that is about 2 miles long. I went up that hill at 40-45 mph empty and it just started to heat up near the top, but, nothing serious.

What would be the first thing to check if I were to start checking things. Any bus mechanics here? I hear the school buses run this combo a lot. I've seen a few single axle fifth wheel trucks for sale with this combo, advertised with a 24 foot grain trailer. After fooling with just 200 bushel at a time, I don't know if I would want to carry 400 bushel with the same drivetrain.


Thanks in advance for any and all suggestions and advice. I really appreciate it.

First check your fluids. Radiator low? oil overfull? The 466's are known for liner pin holing, if the coolant hasn't been maintained. Second check your fan clutch,if it is a viscous drive, and it spins real easy with the engine off,it isn't moving any air. If it is a horton air operated clutch(don't know how the truck is spec'd)make sure it is engaging. If it is a Horton there should be a switch on the dash to override the temp sensor and make the fan lock up regardless of engine temp. The clutches wear out on the Hortons and don't engage, but there is a provision to lock it up manually with a bolt to get you home as a temp fix.
Another thing could be the torque converter is weak and heating up the trans fluid,which in turn heats up the coolant.

Another thing to check,John, is your radiator for fin blockage. You probably have what I call the 1/2 radiator/ 1/2 charge air cooler side by side and they"re notorious for stopping up with dirt/chaff etc. As MSM said, doublecheck the viscous fan drive, can you hear the fan "moaning, pulling harder" at higher temps?

I will check into that. I'm thinking that these are 2 separate issues, after hearing from a buddy that he saw me cropdusting everyone on the highway with blue smoke back in March. At that time, the truck never overheated. He assumed I knew I was blowing smoke like that, and it wasn't until I asked him today about the turbo seals that he told me all this.

I might have been low on water yesterday before I left. I usually pre-trip every thing, every time I drive anywhere, but now I am second guessing whether or not I checked the coolant the last few times. I had to add 2 gallons yesterday, but I assumed I had boiled that much out. Maybe it wasn't there in the first place. I hope I don't have to rebuild the turbo on it.

I just had a thought... could the muffler have an accumulation of oil inside of it and it is burning off? It's brand new. They just put it on.

First thing I would check (after looking for the obvius - coolant leaks and radiator air and coolant flow restriction) is clutch fan operation . When the truck het up did you hear fan running or check to see that it was? Smoking could be due to turbo seals. Pull the air hose to the intake side of turbo and look for evidence of oil - it could also be going in exhaust side and that will make them smoke. Look for evidence of turbo fan hitting housing ( worn tps on fins ) or breakage - if so I'd put a new turbo on before she really lets go.