I have a 1985 Freightliner Daycab, with a 350 Cummins Big Cam hauling logs. My question is this:

When I am pulling up a hill or on a grade the temp goes from 180 normal reading up to 200 and if it is a long uphill grade it will go to 205 and then stay there until I get back down on level ground.

I have had the Radiator flushed out, new coolant put in, checked and ok, my fan motor runs fine had it checked out ok.

Does this hurt the engine, or is it ok? It only does this on a grade or hill, otherwise it stays at 180.

Any advice would be appreciated.

 

I would say it is within normal limits.

Some of the trucks where I work spike up to 210 - 215 before the fan comes on.

That's too high in my opinion, but I consulted the technical literature from the engine manufacturer and it states that that temp is acceptable.

 

Thanks Splitshifter, I was getting worried about this as I was not sure the older engine would hold up to this. I turn my fan on when I know I am going up a hill or grade, and it comes on at 185.

When I get to the job Log Mill, I let it idle for a few minutes to let it cool down and shut it off. Once I shut it off with the temp at 195 and cranked it up after 3 minutes and it didn't seem to want to crank real easy.

Sometimes I sit in line for 10 minutes to 2 hours waiting to get unloaded, and my question is this: What is best for the truck, in other words if I know I am going to be sitting for only 5 minutes is is best to shut off and crank up or let it be longer or shorter.

I don't keep it running for the A/C as mine does not work.

 

i would put fan on until it got to the lowest temp it could , then shut off if your going to be sitting a while. my truck get's to 220 in a hurry if going up hill with a full load. i put in 180 thermo's & took out the stock 190's that helped tremendously during these summer months.

 

My fan is set to come on at 209 degrees. You can set the fan to come on at any temperature you so choose.

 

Old Cummins, high temperature of 205, I wouldn't worry a bit. The old Cummins in my '89 model used to shut down at about 240-250 when I had water problems.

Bad radiator, blown head gasket, broken tensioner, malfunctioning tensioner that allowed the water pump belt to get at a weird angle and break, dirty screens in the aftercooler, blown heater hose, another blown heater hose, another blown heater hose, blown upper radiator hose, and then finally a rotted out steel fitting at one of the water junctions. That was one hell of a truck, but she couldn't hold her water worth a damn.

Just don't push too hard. If the temp is climbing, drop a gear and slow down. (With that bad radiator, I used to have to drop three on a hill I would normally have been able to pull in top gear.)

 

I wouldn't worry about the 205 but if it pushes 220 it's time to get things checked out.

 

I put in a new radiator this past winter. I had to get a winter front because it ran so cool. Now that it is summer, temp runs about 170 even on these 90 degree days we've been having. I was actually worried I was running too cool. New radiator was only $1000 bucks with the surge tank. My truck used to run a little hot also. Now with new radiator I can rest easy when pulling heavy loads or long grades. I think it's a cheap investment for what it will protect.

 

g man.. how do you set fan to come on at a certain temp ? i have a 11.1 det. 60 ser. thanks.

 

The dealer or anyone with a laptop and the Detroit diagnostic program can set your computer up. You will need a password though. If you don't know it, take it to the dealer. They can call the factory and get an override password. They had to do that to mine because I didn't know it.