2005 GMC Sierra 3500 Gas V8 overheating in cold weather

troverman · January 31, 2019

I've had my 2005 Sierra 3500 with the gas 6.0 for about 10 months now. It has 127k miles on it and runs well. This winter I put a Fisher 8.5' plow on it.

Yesterday, I plowed in the morning for about 3 hours without issue. Last night, I drove it about 7 miles up over a moderate hill I've driven over many times. I happened to notice the transmission gauge running about 200F. This is not normal, it is usually around 125-150F except when I'm actually plowing. The truck had sat all day and was totally cold. But I didn't think much of that, since the engine was running good and the truck was shifting fine.

A minute or so later, at the top of the hill, I happened to glance at the engine temp gauge. It was about a millimeter away from entering the red zone. Keep in mind the air temp was probably about 10F last night at the time. Surprised, I turned the heat all the way up, lowered the plow as close to the road as I could, and slowly coasted down the hill. By the time I got home, the engine temp was back to the middle, although the trans temp remained at 200F.

I parked the truck and let it cool off. Went back out later...no visible coolant leaks. Overflow tank was low (fluid in the bottom only) but it has been that way since summer. I added some 50-50 coolant. Pulled on the plastic fan blades...they are tight, so I'm assuming the water pump is OK. Now, the fan seemed to turn easily despite the engine compartment still being pretty hot. The top radiator hose was hot.

I took it for another drive later up the same hill. At the top of the hill, the engine temp was a little beyond the middle point (maybe reading 220F) and the trans temp was at 200 again. So something is up. Thoughts? I'm thinking the following possibilities:

1. Radiator plugged or partially plugged

2. Thermostat not fully opening

3. Viscous fan clutch not engaging fan properly (although it was so cold, why would it even need the fan?)

JoJoJim · January 31, 2019

Just curious. Have you checked the oil cooler radiator to make certain that it is not plugged with snow or ice? Worthy of a look.

davester · January 31, 2019

I recall a post somewhere about the plow itself being the problem, in that it blocks airflow while driving around.

google "gm truck overheating with plow"

troverman · January 31, 2019

I guess it could be the plow, not sure. It was pretty darn cold last night.

Is the oil cooler the small, vertical cooler in front of the radiator / condenser? Nothing was plugged with snow or ice, I checked that.

I'm assuming the transmission heated up because it's cooler is inside the radiator?

Thanks

davester · January 31, 2019

depends on the options you have.

my truck has a narrow, tall cooler on the driver's side, that's the PS cooler, more squarish oil cooler in the middle, a/c cooler behind these two, main radiator in back.

troverman · January 31, 2019

OK, so the tall narrow cooler is the PS cooler on the left side. My truck has A/C so it will have that. Not sure about the oil cooler. Will check. Being a 3500 cab and chassis, I'd assume it does.

Formulabruce · January 31, 2019

1 hour ago, davester said:

I recall a post somewhere about the plow itself being the problem, in that it blocks airflow while driving around.

google "gm truck overheating with plow"

Exactly the case here. One remedy is to put a larger cooler on the transmission . its just behind the grill and easy to upgrade to one twice its size.

Its on the middle bottom. A B&M super cooler will bolt right up and a couple zip ties and your all set.

Also, the 8 ft plow pretty much blocks all the air to engine ., Bruce in NH

PS a 160 T stat can help with this too. I used to run one in the summer when I was towing a lot. Doesnt make a bucket load of heat though in winter

riverbanks · February 1, 2019

You said,that it has a mechanical fan clutch,go for a new one,ive seen plows on in summer,like a new purchased vehicle,coming home from dealer with no problems

Z45 · February 1, 2019

15 hours ago, davester said:

I recall a post somewhere about the plow itself being the problem, in that it blocks airflow while driving around.

google "gm truck overheating with plow"

Yep, plow will do it. Been there on that. Have to drive slow. I recall the first time was when was driving home after having it installed. In less than 5 mi the the truck overheated.

I tried everything, big fan clutch, bigger radiator, nothing helped, all it did was cost me more money. Drive slow and adjust the plow height for best air flow or take if off when not needed. Mine worked best when the blade was as low as possible.

troverman · February 1, 2019

Thanks guys. I am going to try driving with the plow lower when I need to go 50 mph. Most of my plowing route is just around town and it doesn't seem to be a problem. I have an 8.5 foot plow on it.