Fan engaged today and hit 200 degrees on Cummins 8.3 for first time....why??

[Oldworldtenacity]

Ok, So I had the truck out for a couple hours this evening between 6-8 after it sitting for 3 weeks and it ran just fine. Engine temp stayed between 170-180 driving around and stopping at red lights for 2-3 mins at a time sometimes.

It seemed to take forever to warm up during the late Winter months...even when I drove it all the way back from GA.

WHen I got it back home, I left it running for about 10-15 mins when All of a sudden I heard the fan engage...and I was like...WTH...jumped up in the truck and sure enough it was just shy of 200 degrees. I was done with the truck, so I turned it off anyways.

It was only about 77 degrees at the time...so I guess I can forget driving it when it's 90-95 out...unless this can be resolved. It only has 6000 miles according to speedo and rebuilt in 2011...and supposedly uses little to no oil as the oil had not been changed in 5500 miles until I changed it and it was full.
I was surprised that this happened...however, I am not much of a mechanic.

I did not think that these engines would be this tempermental in warmer weather...even when idling for a bit.

Maybe I am being a bit harsh of a critic on the engine at this point since it is the first glitch I have encountered since I bought it in FEB.

 

[Suprman]

That's what's supposed to happen. When you were driving air was moving thru the radiator cooling the system. When idling not moving you don't get the same airflow as driving. When you get to around 200deg the fan automatically comes on. Usually only for a short time it moves a lot of air and the temp will drop fast.

 

[sandcobra164]

They have tried to make the diesel trucks run warmer as an attempt to get cleaner exhaust. My National Guard M1089A1P2 will make it's fan holler once warmed up and running down the road. The fan cuts in at about 210 or so indicated and cuts out around 180. Once the fan kicks in, you can watch the gauge ease back down. I don't think anything is wrong with your truck. At least you get some quiet time. My Deuce has it's fan on from the moment it starts as there is no fan clutch so it's always loud when rolling down the road.

 

[74M35A2]

Change your thermostat. Low cost and easy to do. I did mine when I thought my old one was behaving correctly, and my slow warm up went away. Warms up much faster now, even in the winter. My fan was coming on at warm idle like yours, and may still do it, as I just changed the stat this winter.

As a reference, my A2 reaches 180F reasonably quick now if driving, and can even hold it solid while going 67mph in 4F temps with no grill cover.


If you have a slow warm up while driving, you need a thermostat change.

 

[Oldworldtenacity]

That's what's supposed to happen. When you were driving air was moving thru the radiator cooling the system. When idling not moving you don't get the same airflow as driving. When you get to around 200deg the fan automatically comes on. Usually only for a short time it moves a lot of air and the temp will drop fast.

Well, I just thought it seemed strange that it got that warm when it was only 75 out with low humidity. If it was 90+ I might have expected it....I'm not used to Diesels, so maybe I'm just being to critical at this point.

With the gauge only going to 240(I think)...200 seemed to be getting up there for just idling...feel free to scold me though lol.

 

[Oldworldtenacity]

They have tried to make the diesel trucks run warmer as an attempt to get cleaner exhaust. My National Guard M1089A1P2 will make it's fan holler once warmed up and running down the road. The fan cuts in at about 210 or so indicated and cuts out around 180. Once the fan kicks in, you can watch the gauge ease back down. I don't think anything is wrong with your truck. At least you get some quiet time. My Deuce has it's fan on from the moment it starts as there is no fan clutch so it's always loud when rolling down the road.

That is interesting to know as I did not know that those newer models ran that hot...also did not know that about the Deuce's either.

 

[Oldworldtenacity]

Change your thermostat. Low cost and easy to do. I did mine when I thought my old one was behaving correctly, and my slow warm up went away. Warms up much faster now, even in the winter. My fan was coming on at warm idle like yours, and may still do it, as I just changed the stat this winter.

As a reference, my A2 reaches 180F reasonably quick now if driving, and can even hold it solid while going 67mph in 4F temps with no grill cover.


If you have a slow warm up while driving, you need a thermostat change.

I was wondering about the Thermostat, but I don't know how to change them or where to look. I'll tell my mechanic to change it soon per your advice and reference. I had to put a piece of cardboard over half of the radiator to get to it to 170 driving back from GA in late FEB in 20 degree weather at 70mph.

 

[Bandit02]

Typically, these diesel engines don't get all that warm running empty/idling.

When I'm bob tailing my 931' it doesn't warm up fast until I hit a hill and put the load on or pulling a heavy trailer. Most fan-stats are tripped at 210* and it's good to see yours works.

If your getting 200* idling I suspect your thermostat is stuck in the closed position and not letting your coolant flow to your radiator.

 

[74M35A2]

I was wondering about the Thermostat, but I don't know how to change them or where to look. I'll tell my mechanic to change it soon per your advice and reference. I had to put a piece of cardboard over half of the radiator to get to it to 170 driving back from GA in late FEB in 20 degree weather at 70mph.

Sounds like your stat is flunky. Have it changed and report back. You should have enjoyable results. Likely won't need to change the "seal" that is within the thermostat cavity, just the thermostat and gasket. It is under the housing that connects to the upper radiator hose on the engine. Easier if you remove the alternator, but not necessary. Our 6CTA8.3's use a single thermostat (others use dual).

 

[dawico]

You may need to flush the system and replace the coolant too. Mine was full of rusty water and the thermostat started sticking. Too much junk floating around in the system.

 

[Moto2four]

There is an air bleed line that goes from the top of the cold side of the rad to the overflow tank. Mine was clogged and caused the rad to air-lock. I replaced the water pump and t stat and pulled the end caps from the radiator to clean it out. It took me hours to figure out I had a simple issue. Hope this helps.

 

[NJDEUCE]

I'm having the same issue. I recently replaced the air compressor in my truck (923a2), which requires draining the coolant. Afterwards I filled the system back up, and purged all the air that I possibly could. Anytime I drive the truck now it warms up to 200 and kicks the fan on, which I had never even heard before. I might try replacing the thermostat, but Moto2four's suggestion is definitely something I will look at first.

 

[dawico]

There is an air bleed line that goes from the top of the cold side of the rad to the overflow tank. Mine was clogged and caused the rad to air-lock. I replaced the water pump and t stat and pulled the end caps from the radiator to clean it out. It took me hours to figure out I had a simple issue. Hope this helps.

I had the same issue too. When I cleared it it actually had green coolant in it. The rest of the system was just rusty water.

The fittings are a pain to deal with and cause the clog.

 

[NJDEUCE]

There is an air bleed line that goes from the top of the cold side of the rad to the overflow tank. Mine was clogged and caused the rad to air-lock. I replaced the water pump and t stat and pulled the end caps from the radiator to clean it out. It took me hours to figure out I had a simple issue. Hope this helps.

I pulled this line off today, and just like you said, it was clogged solid. I couldn't believe it! The clogs were at both of the fittings, but more so at the expansion tank side. I literally had to use a drill to clear the clog it was so hard and deep. It came out as black dust. It was easy to tell that this was the problem because as soon as I cracked the radiator side fitting, immediately I had air purging out and coolant being drawn from the tank. Thanks so much for posting this, it saved me a lot of troubleshooting and probably money!

 

[Moto2four]

No problem, I'm glad it was an easy fix.

 

[Carlo]

I thought my anti freeze was in perfect condition. Nice and green TILL I drained it one day and found the sludge at the bottom of the radiator. That week I flushed every truck I have and found them all to be the same. I also checked thermostats and all worked poorly from the crud and rust. I cleaned them all up and had no more high temps.
You can also adjust when the fan kicks on but pulling the actuator and adjusting or turning it in towards it's housing so the fan comes on at a lower temp. Go on search and you will find threads where other members have done this.

 

[Moto2four]

Has anyone experimented with the fan set points? I know that with some diesels you can raise the fan set point a bit and squeeze some more efficiently out of them.

 

[Bandit02]

I thought my anti freeze was in perfect condition. Nice and green TILL I drained it one day and found the sludge at the bottom of the radiator. That week I flushed every truck I have and found them all to be the same. I also checked thermostats and all worked poorly from the crud and rust. I cleaned them all up and had no more high temps.
You can also adjust when the fan kicks on but pulling the actuator and adjusting or turning it in towards it's housing so the fan comes on at a lower temp. Go on search and you will find threads where other members have done this.

I replaced my fan-stat valve a couple days ago with a civilian version made from Haldex, it was leaking air constantly through the exhaust port. It's a bit longer then the military one but opens at 185*, the end is adjustable and if you turn it in it supposed to raise the temp by increments of 5*. The military one is selling for around $250 US but I got mine at a local Western Star/Freightliner dealership for about $50. The only difference is it's a bit longer so a pipe fitting extension is needed.



http://www.haldex.com/en/North-Amer...arts/Temperature-ControlsShutterstats/RF36029

 

[Oldworldtenacity]

Today was the first day I got to run the truck since this happened. It was raining..so didn't bother opening the hood. I drove it around for an Hour or so and it was about 70 degrees today.

It never got above the 182-183 degree range. I still plan to follow the steps mentioned here the next nice day we get.

 

[Oldworldtenacity]

Today was the first day I got to run the truck since this happened. It was raining..so didn't bother opening the hood. I drove it around for an Hour or so and it was about 70 degrees today.

It never got above the 182-183 degree range. I still plan to follow the steps mentioned here the next nice day we get.

Also, I just read in the TM where it says the Thermostat shuts off coolant flow to the radiator until the temp hits 181 degrees on M923A2 trucks....so I guess it was running totally normal on Sunday.