6.6 Cooling fan issues

[harryschopshop]

Hey, i'm having an issue with a 6.6 in a 2007 C4500. The engine is an LMM ( i think...the 8th digit is 9). I'm getting a P0480 DTC. The cooling fan is not kicking in.

The engine temp only goes to 170 when idling...on the interstate though, it gets hot and shuts down the engine. Not sure what the engine temp when it shuts down, but it doesn't appear to be over 220 by the guage. Everything appears to be working as designed according to the tech II, except for the operating temp at idle.

The radiator, water pump, fan (and clutch), coolant sensor, egr valve, egr cooler, condensor, accumulator, orifice tube, and ac lines have all been replaced.

The 5v circuit is good according to the tech II and I'm assuming the relay is good as I can command the fan to 100% manually and you can hear it roar.

Has anybody seen anything like this?

[Kennedy]

Is there actually anything electric about the fan or fan clutch on that truck? I thought al of the Dmax trucks pre 2011 were full mechanical?

[harryschopshop]

Nope, it's electrical...

[harryschopshop]

Ok, I drove the truck down the highway. Fan is kicking in as desired according to the tech II. Unit does not get over 190 degrees, so no overheating condition. Driving down the highway at sustained speed (55, 60, 65, 70 mph), the green DPF light is illuminated.

After 5 minutes of sustained driving at the aforementioned speeds, two of following three things happen...
1.) The check guages light comes on under hard acceleration (for example, passing) and it goes out when you decellerate and

2.) The check guages light comes on and stays on until you deccelerate (appx 5 mph) in which case it goes out or

3.) The check gauges light comes on, stays on and the engine shutdown light comes on and shuts down the engine. In the shutdown situation, the engine will immediatly restart.

Once the above happens, the check gauges light comes on under any hard acceleration situation, for example takeoff from a stoplight.

Thoughts?

[Kennedy]

About the best I can say at this point is get out and drive until the DPF light goes out.

I'd like to see a picture of the electric fan setup if you would.

[More Power]

Ok, I drove the truck down the highway. Fan is kicking in as desired according to the tech II. Unit does not get over 190 degrees, so no overheating condition. Driving down the highway at sustained speed (55, 60, 65, 70 mph), the green DPF light is illuminated.

After 5 minutes of sustained driving at the aforementioned speeds, two of following three things happen...
1.) The check guages light comes on under hard acceleration (for example, passing) and it goes out when you decellerate and

2.) The check guages light comes on and stays on until you deccelerate (appx 5 mph) in which case it goes out or

3.) The check gauges light comes on, stays on and the engine shutdown light comes on and shuts down the engine. In the shutdown situation, the engine will immediatly restart.

Once the above happens, the check gauges light comes on under any hard acceleration situation, for example takeoff from a stoplight.

Thoughts?

There's got to be other codes being set besides the fan...

[harryschopshop]

There may have been a couple more codes. I can't remember, but I believe I wrote them down. I'll check the paperwork on Monday.

now that you mention it, the green light came on almost as soon as I got on the highway and didn't go off until I got back to the garage and stopped...strange...

I'll take a pic of it Monday morning and see about e-mailing it to you Kennedy. I thought all of them had it. I have one 2004 and four 2007 models I maintain. All the 07's have them and this particular one has been changed and I had the pleasure of doing it. Not sure about the 04.

Seems like I just did an oil change on this one a few months back. Have to check the history. the oil pressure did seem a little on the low side...around 40 psi at highway speeds if I recall correctly. More to follow.

[Kennedy]

My experience with the Medium duty trucks has been pretty much limited to ECM programming. Many are done via mail order, but I do have some locals that have popped in. I never really looked at the cooling, but am surprised to hear about electrical fan clutch engagement or cooling fans.

[harryschopshop]

The GM number for the fan clutch is 9467-1205. It's an expensive little bugger too. Around $400 list, but it is no longer available w/o replacement. Heres the link... http://parts.nalleygmc.com/showAssem...category=19395

I had cleared the code Friday before I went home. I was out yesterday and the tech drove it. The only code was a P0480. I did find the engine oil overserviced a bit, no fuel in it that I could smell. That could explain the oil pressure reading. the check gauges light works off of high coolant temp and /or low oil pressure. The PM was done back in October and the unit has about 6000 miles on it. I'm gonna change the oil and filter (we also use recycled oil and Somstech Microgreen filters). I should have another update later today.

[More Power]

.....I did find the engine oil overserviced a bit, no fuel in it that I could smell. That could explain the oil pressure reading. the check gauges light works off of high coolant temp and /or low oil pressure. The PM was done back in October and the unit has about 6000 miles on it. I'm gonna change the oil and filter (we also use recycled oil and Somstech Microgreen filters). I should have another update later today.

I watched the online video for the MicroGreen oil filter... Looks impressive, but I would recommend using a conventional AC Delco oil filter and brand new API diesel-rated motor oil as a test for the oil pressure issues. If the symptoms are the same, then it's not due to the aftermarket oil filter or recycled oil.

Unless the used motor oil is re-refined and meets the API diesel specs for new motor oil, I wouldn't use it in any engine I cared about.

[harryschopshop]

Let me tell you, I wouldn't use those green filters or the recycled oil if you gave me enough to do ten years worth of oil changes. I am a contractor (for who, I can't say) for a major corporation (who, I can't say as I'll get in trouble) and they say we have to use the stuff. We went from 6 mos/6000 miles to 11 mos/18000 miles on our oil changes. Not a smart move, but what do I know, I'm just a grease monkey.

To the matter at hand, I spoke to the tech and neither he nor I have had to add oil to this engine which begs the possibility of a leaking injector or two (or more). After the oil change (recycled oil and a napa filter) he drove it in the same manner in which I did. the problem is gone (for now) hopefully for good. Time will tell. The oil didn't smell of fuel and wasn't too thin, but we shall see. It would seem that the excess oil and a possible clogged filter caused the low oil pressure (40 psi @ 55-70 mph highway). The check gauges light works off of high coolant temp or low oil pressure. I'll revisit this thread if it comes up again. Thanks.