Engine/temp Gauge Issues

Canned Heat · January 9, 2008

Took delivery of '07 Sierra Crew Cab w/ 4.8 about 3-1/2 weeks ago. 2 weeks ago I hit the remote start(factory) and 8 or 9 minutes later go out and find the windows still frosted and the fan blowing cold air. Put key in, gauge turn over and temp reads 225 or so...well past the 212 mark it's usually maxxed at. Take it in and they tell me it's a faulty thermostat...concerned at that point but...it may happen on occasion and I know the truck sat on the lot a little while, OK. Now, a week removed from that and I fill the tank this morning. Start it up and go in for a coffee and pay for the gas. I come out and I can here the fan roaring (it's 21 degrees out!) and sure enough, temp gauge is reading 220-230 again. Drive while monitoring temp and get not even a mile away and temp is back to 212 and never fluctuates the whole time. Talked to service manager this morning and he's at a loss for words. The 4.8 is the devil....My 5.3 was the ****.

Anyone else have this issue with an '07 or a 4.8?

C & A s Dad · January 10, 2008

I am just offering my opinion and/or idea here. I am hoping a Prof Tech and chime in and offer some more solid advice.

I think you are seeing the result of the e fans. They are likely designed to come on around 220 or so and when an E fan equipped vehicle is at idle there is absolutely NO air flow through the radiator with the exception of a good breeze blowing outside. The fans kick on and your temp drops. My Caravan that I drive for work does the same thing. If at idle, the temp gauge will move way up sometimes and then I hear the fans kick on and I can literally watch the needle fall to a normal position.

With a manual fan and a clutch, even when the clutch is "free wheeling" it is still allowing the fan to rotate at a pretty good rate. It is slipping to some degree but it is still pulling some air through the radiator. Of course, once the temp rises, the clutch locks up allowing full flow from the fan.

Persoanally, I do not like e fans at all but do realize on a FWD transverse mounted engine, there is no choice. I also realize on a real vehicle, like our trucks with the proper wheels pulling and the engine mounted the way it should be, GM has chosen the e fans for greater economy and to allow more HP to get to the wheels. They evidently do the job because they have been using them now for the past 3 or 4 years. Call me old school, but I just like that big mechanical fan up front which has the capability of pulling small animals into the grille if they get too close.

Canned Heat · January 14, 2008

I have the same issue last Friday....again. Take it to the dealer garage on the way home and nothing. Start it up this morning with remote and it runs the 10 minutes and shuts off. I start it again and get outside after a few minutes and it's ice cold and blowing cold air. Flip the key to activate the gauges, etc. and within 30 seconds the temp gauge is reading 225 or so. I get a couple miles down the road and the heat finally kicks in, and the temp gets back to 210-212. I stop for a coffee and when I come out after 2 or 3 minutes the fan is cranking and the temp is way up again. Called and talked to my sales rep buddy and he tells me another guy (who I actually know) had the same issue after leaving his at O'Hare for a week. Both 2007 Crew Cab Sierras. I didn't ask if he had the 4.8...should've. This truck is absolute crap compared to my '02.