truckjunkie

Hi guys - the weather's starting to warm up here, and I've just driven the truck a couple of times with the A/C on. It appears that, especially while on the highway, the truck seems to run slightly warmer with the A/C turned on. Generally speaking, the water temp gauge runs about two needle width's below 200 degrees (middle of gauge), and when the A/C is on, it maybe runs a needle width or less below half. Are some of you guys seeing this as well? It just seemed that the A/C shouldn't affect this truck that much. And since I haven't really towed anything significant with this truck, I don't know how it acts towing a trailer in warm weather either. Dunno - maybe I'm being paranoid. I'm wondering if I need to do a pressure test on the cooling system.... What do you guys think?

crobtex

How dirty is your radiator? Flush it from the "backside" with a water hose. I blew a lot of junk out of mine and it runs much cooler now.

zog

My 2004 does the same....I would not think a 2004 would need a radiator flush unless there are a gazillion miles on it....I have 4300 on mine...

pullin hard

i think that is normal , and i noticed that too taday.
when running the AC, it puts a little more load on the engine, as the clutch is engaging and disengaging, and the fan clutch is doing the same, witch robbes power, and puts more load on the cooling system.if it is only going up a bit, thats ok, if it goes up alot, thats a problem.

truckjunkie

OK, so if there's a slight increase in temperature with just the A/C on, how much does the temp increase when towing a heavy trailer? I haven't towed anything heavy in warm weather yet.....

SuperGewl

Highway running with the AC on and I don't see any change in the temperature gauge. The only time I see anything change is when backing the 5VR into a spot if I move it in & out too many times

bulabula

My needle has moved up like that since it was new. I wouldn't lose any sleep over it.

Crobtex wasnt referring to flushing the inside of a brand new radiator out, but to flush out any old leaves/dirt/debri that may have found its way between the cooling fins and impeding air flow through the radiator.

Hal

Mine actually seems worse than that, even without the AC. Normal winter driving needle stays between the 2 and the 0 (about 195?). Warm days driving in traffic/hills in CO/slow 4 wheel drive roads/towing I run between the zeros (about 205?).

A 10 degree movement seems pretty high, especially without any significant load. Never noticed that type of swing in previous trucks unless the thermostat was going bad.

Anybody else see this? I'm thinking I should call the dealer to see what they say before I tow on the holiday week.

RamWheelsBy4

Mine does the same thing. The guage is not accurate to any degree that y'all seem to be reading it. Mine swings from a couple of needles below the 200 mark to a couple of needles above it depending on what I am doing and if the AC is on.

When I set the Attitude to monitor the Engine temp I see the dash guage in a little different light. When the dash guage has move maybe a needle past the 200 mark, the computer is showing maybe 198. I just would not worry until it starts really moving to what could be read as 210 to 220.

bigblock2stroke

The fan doesn't come on for coolant temp control until 215. Engine is designed to run at 229 without defueling.

A 10 degree swing is not that much. Especially when you thorow in the accuracy (rather inaccuracy) of the sensor and the variability of the thermostat.

underwoodtransp

every person I know with a newer cummins does the same thing. Even when empty if you goose it from a dead stop the temp will rise to about even with the 200 mark then when up to speed it will cool back off. I agree with bulabula I wouldn't loose any sleep over it. I see my gauge over 200 all day long and I have never shed a drop of sweat from my brow!

msilbernagel

bigblock2stroke ,

Does this mean it defuels at 230 degrees?

Thx,

Mark
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handymantim

The A/C condenser (radiator) is the one in front of ALL the other radiators. In addition to increasing engine load, running the A/C increases the air temp flowing past ALL the other radiators.

The temp gauge needle is controlled by the computer. It is not a direct reading.

Smkndzl

on my truck , when it is running two needle width before the line , the engine is running right at 201 , and when it reaches a needle width past the line the engine is running at 207 , that is the hottest I have seen with outside temp of 100 and pulling the hills empty.

Haulin_in_Dixie

Every thermostat that I have ever seen on a Cummins has about a 10 degree droop from low thermostat to full open position. Truck empty, no load little heat it will stay 10 degrees or so low. Add a good load on a hot day or turn the air on and it will go up to full open position.

Some of the thermostats have a larger droop to them. In the winter they never seem to get to the higher temperature. I have a 180 degree thermostat in mine and it gets to 190 max. Light loads it stays at 180.

I have found that the thermostats that regulate better at operating temperatures take forever to warm up. The faster warm up thermostates are more ragged on the operating temperature level.

You will also find that some thermostats are marked 180-190 and some are just 180. The OEM thermostates that Dodge picks out for the engines are less effective at loads and high temperatures. They do have a fast warmup though.

I have had the best luck and more stable operating with the commercial thermostats that are made for the cpl2080 engine. My experience with the OEM thermostates are that they are all over the board and get very hot pulling loads.