M929 A2 over heating problem

[T2C]

Hi all. First time poster, hope I'm posting in the right place. Thank you all for teh information on this site. I've recently become the caretaker of an M929 that's been converted to a water truck. We've been experiencing some overheating when hauling our load slowly, ( usually not leaving first gear), and when dispensing water in low transfer. I noticed the other day that as soon as the gear shifts into second the temperature drops immediately back to the normal range. Is this normal, or is something malfunctioning? Does moving into higher gears spin the fan faster, and cool better. Our ambient temps here have been about 100 degrees, which may be part of the problem.
thank you

 

[Scar59]

Yep, you have several issues, that combined will lead to high temps. Low engine speed will result in low fan RPMs = low air flow through the radiator. AZ outside air temps add to this. The fan will not engage until the thermostat opens and engages the fan clutch, this will occur @ 185 F. Does the engine overheat light come on?
If not, the engine is getting warm but not overheating. Temp gage may not be that accurate.

 

[Jbulach]

Welcome for Indiana!

What RPM are you typically running while dispensing water in low range? Is the fan engaged the entire time? Also have you noticed where your transmission temps have been at, while the problem has been occurring?

 

[T2C]

Thanks Jbulach, and Scar59. I'll check on the RPMs when dispensing today. The engine overheat light does not come on. The transmission temp is close to 200. The fan seems to be operating normally. Anyway to tell if fan is on while operating without getting out to look at it? Recently replaced shutter stat leaking air, don't think the fan was running right before that.

 

[BKubu]

You can usually hear it when the fan comes on.

 

[Scar59]

Thanks Jbulach, and Scar59. I'll check on the RPMs when dispensing today. The engine overheat light does not come on. The transmission temp is close to 200. The fan seems to be operating normally. Anyway to tell if fan is on while operating without getting out to look at it? Recently replaced shutter stat leaking air, don't think the fan was running right before that.

This sound like the truck is operating as designed. No overheat light, trans temp @200. New shutter stat, just ensure the fan clutch is engaging, fan will produce a louder sound, pulling air. Work that truck.

 

[Jbulach]

This sound like the truck is operating as designed. No overheat light, trans temp @200. New shutter stat, just ensure the fan clutch is engaging, fan will produce a louder sound, pulling air. Work that truck.

Scar59
Where is the "overheat light"?

T2C
Yes, the noise of the fan should be very obvious when it engages. How hot is your engine temp reading?
If it hasn't already been done, especially with your operating environment, you should consider doing a coolant flush and change, a lot of these trucks had extremely sludged up cooling systems.

Also, get a handheld IR thermometer so you can check your temperature's at least on both sides of the radiator and transmission cooling lines to help verify your operating temperatures and the gauges in the truck.

It sounds like you are likely running the truck at very low speeds, so I would recommend you run in lower range as much as possible, to prevent lugging the engine and generating heat in the transmission. Just don't forget not to run in reverse while in low range!

 

[Scar59]

Eng ovht. Red lens on the bank of warning lights above the steering wheel??

 

[T2C]

Just made it home from another day of trying to avoid major catastrophy with this truck. Thank you all for your input. I was able to read it all at lunch, but didn't have good enough signal to respond. It was great to know what to keep ab eye out for. I'm running between 1200, and 1500 rpms in low transfer while dispensing water with the PTO. The engine temp runs between 175, and 200 when I get it moving well. After dispensing, it is around 220, that's about when I start to sweat. Thought I was having a problem hearing the fan running, so got out and checked when it was around 220. With the truck running in neutral, the fan wasn't spinning. Pretty sure I'm hearing it kick on at the transmission change at 30mph, (3rd gear?). That brings the temp down to 175-200 pretty fast. Later I checked the fan between 175 and 200, and it spun very slowly, almost like it was just getting blown by the wind. I found that I don't have an engine overheat warning light, one spot is blacked out behind the steering wheel. There is one between the tach, and speedometer. But I assume it is for the tach. Tried to run a load of water in low transfer. I didn't feel that it shifted at the right time, or was going fast enough. Noticed the heat climbing too. Shifted back into high for the last half of that run. The truck seemed different as it got later in the day. It seemed bogged down, and wasn't shifting at the same places it was early in the day.
Jbulach: I saw the warning about not using reverse in low transfer. So, like a good monkey, I just didn't. Do you know why? If not, I'm fine with just not doing it.

 

[T2C]

Will definately flush, and change coolant. Thank you

 

[Suprman]

Put a A1 185 degree shutterstat in. Direct swap. Get the fan going earlier.

 

[T2C]

I told my partner, (at work). You tag line, or whatever it's called. The thing about the stupid people. His eyes lit up like he'd never heard a better idea in his life. I feel the same. Of course I needed the warning about reverse in low transfer. But I'm willing to roll the dice, and see where I end up.

 

[T2C]

Do you know when the A2 stat kicks in? Just put $250ish into the new one, and probably can't send it back now that it's been used. But wish I knew it was better before I'd ordered. Any other parts better that fit on either on the A1, or A2? Have an A1 personally, and like it better for what's done around here. Heavy hauling at lower than 30 mph. No turbo, no turbo problems. Mo machinery, mo problems.

 

[Suprman]

Suppose to be 210 or 215. I used the flir on my motor one day I thought mine was running a bit hot. The block was over 220. The upper pipe where the shutterstat is located was lower temp though. The shutterstat isn't is the ideal place to begin with. 220 is too hot for the 8.3 that's why the coolant gets burnt and sludgy. The big radiator is designed to cool the older larger Cummings 250. It should easily keep the 8.3 at a good temp. The 185 degree stat helps.

 

[Jbulach]

Just made it home from another day of trying to avoid major catastrophy with this truck. Thank you all for your input. I was able to read it all at lunch, but didn't have good enough signal to respond. It was great to know what to keep ab eye out for. I'm running between 1200, and 1500 rpms in low transfer while dispensing water with the PTO. The engine temp runs between 175, and 200 when I get it moving well. After dispensing, it is around 220, that's about when I start to sweat. Thought I was having a problem hearing the fan running, so got out and checked when it was around 220. With the truck running in neutral, the fan wasn't spinning. Pretty sure I'm hearing it kick on at the transmission change at 30mph, (3rd gear?). That brings the temp down to 175-200 pretty fast. Later I checked the fan between 175 and 200, and it spun very slowly, almost like it was just getting blown by the wind. I found that I don't have an engine overheat warning light, one spot is blacked out behind the steering wheel. There is one between the tach, and speedometer. But I assume it is for the tach. Tried to run a load of water in low transfer. I didn't feel that it shifted at the right time, or was going fast enough. Noticed the heat climbing too. Shifted back into high for the last half of that run. The truck seemed different as it got later in the day. It seemed bogged down, and wasn't shifting at the same places it was early in the day.
Jbulach: I saw the warning about not using reverse in low transfer. So, like a good monkey, I just didn't. Do you know why? If not, I'm fine with just not doing it.

No overheat light on my A2 either, you should have a "overspeed" light for the CTIS to the right of the speedometer.
It's very common for the fan to coast and turn slowly while not engaged, it's usually quite obvious when the fan engages, especially at higher rpm.
The M939 series trucks are known to break the transfer case housing while using reverse in low range. Some have been fitted with a lockout mechanism to prevent the truck from going into reverse while in low range.

 

[T2C]

I have the overspeed light, but also another above, and between the tach, and speedometer. Again, pertty sure it's a high rpm warning. So do you think that it's the fan clutch that's the issue? My shutter stat has 190 stamped on it, so i think my supplier helped me out without explaining. Thanks for the info on the transfer case reverse. I'll definately continue not doing that.

 

[topo]

Can you run a hose from the tank or pump to front of the truck and let water run down the radiator .

 

[T2C]

I was hoping that something was defective, and I could solve it with a part. I seems that I am just running the truck under heavy load in poor conditions, (high ambient temp). I think just about everything but the garden hose is in place for us to be trickling water on the radiator. Thanks for the great idea.

 

[Suprman]

I have some slim high flow fan you could prob mount on the front of the radiator.

 

[T2C]

I have some slim high flow fan you could prob mount on the front of the radiator.

Can you send a pic, and/or dimensions of that? So i can check to see if it will work on Monday. A price as well please. Thanks