EGR and Cooling Fan Correlation

Keith Browning · May 3, 2013

With regard to 6.0L engines I have read many times that disconnecting the EGR valve or installing a dummy valve can cause issues with the cooling fan and reports of engines running hotter than normal. I have never tested this nor have I had the opportunity to. But I also wonder if an EGR system failure can cause the PCM to act in a similar way if this is true.

I have a truck in my shop, a 2005 6.0L with 260,000 miles that the customer has been seeing higher than normal temperature readings, almost at the "H" on the gauge but it never actually overheats or expels coolant. New pump, clutch, t-stat and I cleaned a lot of bugs and dirt from the cooling stack. The gauge (for me) never leaves the mid-range but the fan comes on and stays on.

According to the customer all of this work was just done and the fan was on the entire trip from Missouri to New Jersey shutting off only once or twice. I was looking at PIDS on this thing and EOT and ECT were both under 200 and the fan was still staying on.

I had a couple of DTC's related to EGR, one for the throttle plate actuator and a P0401. So I began playing with active commands and looking at things working. Long story short all of the moving parts and sensors work fine but IAT2 does not change. I removed the EGR valve and commanded it open, and it did. I then started the truck and discovered the cooler has no exhaust flowing through it but the port looks clear. Obviously the cooler is blocked...

Any thoughts on a correlation here? I am perplexed. Posted Image

Aaron · May 4, 2013

Cooling fan going to beat the band will impede airflow through the radiator at road speed, eventually causing an increase in temperature. Possibly engine goes into self-preservation mode and ramps up the fan when it sees certain DTC's?

Or maybe the fan clutch is dicked and staying on, and the over temp and EGR issue are just a coincidence.

Keith Browning · May 4, 2013

Don't forget the EGR cooler is restricted on the exhaust side. It definitely needs coolers. For now I replaced the fan clutch, cleaned a ton of dirt out of the cooling stack and updated his mismatched module calibrations (has a new FICM) The guy is taking it to leave to return to Missouri on Monday. Hope he makes it. I wanted to see the oil cooler...

Aaron · May 4, 2013

I wanted to see the oil cooler...

Oh, you likely will, or someone along the Missouri route will. LOL

GregH · May 4, 2013

With ECT and EOT both around 200, the fan may be commanded on for other reasons. A/C head pressure or TFT?

Is the fan being commanded by the PCM, or is it locking in on its own?

Moot, probably, since its gone....

Aaron · May 4, 2013

True, never thought of that. Monitoring fan speed VS. duty cycle.

Keith Browning · May 4, 2013

The fan operation was the point of my post. On my first road test and then running in the lot at high idle the fan came on... like it should have but then after several minutes it did not go off like every other truck I run like that in the lot. I let it idle, goosed the throttle and the fan stayed fully engaged. I shut it down. Tried again later in the day, fan still locked upon startup.

Even though it was new I replaced it for that reason alone. Duty cycle was 0% when I checked it and the fan speed looked like it was correct.

I thought about TFT - peeked at the PID and it was good even though the fan command was at 0% with the fan locked it seemed like something I needed to look at. A/C was off the whole time. It did the same thing with the new fan clutch but at least then I could command it on and off with IDS and it did not "stick on" when I shut it off.

Strange one indeed. If I remember maybe I will ask my writer to call them in a month or two to see if they figured it out and what they did to it.

vloney · May 5, 2013

Where at in Missouri are they going to?

Aaron · May 5, 2013

Waynesville.

vloney · May 5, 2013

I'll let you know if we get anything in like that. Got lots of indie garages here that "specialize" in 6.0s.

Aaron · May 5, 2013

I was just pulling your leg, dude Posted Image

vloney · May 5, 2013

Yeah, I know. We get just enough 6.0 work in here where you can remember each one. Been a long time since we done a water pump. Lots of FICMs though.

blown99 · May 7, 2013

I have run across this a few times with guys that installed egr deletes. If I remember correctly, they were 04 MY trucks. Everything worked fine until they installed the delete kit. They ended up having a custom tune written for them and installed it to repair the egr to fan issue.