Thread: 2008 grand prix (base) running hot.

I have a 2008 grand prix with the 3.8 v6 base model with 70k miles. i noticed that the car is running a bit hot in traffic but highway driving its on the half mark. i have changed the coolent temp sensor and the thermostat with ac delco oem parts. did not fix the problem. also did a full coolant change before past winter. i have no idea where to look for from here. it goes beyond the half mark and the fans kick in dropping the needle back to the half mark then climbs up again. my next thinking was that could it be due to a little bit sticking radiator cap causing the pressure inside to be more than the oem pressure so it tends to heat up a bit? does our cars have two stage fans ? kicks in at a low rpm at a lower temp and higher rpm at a higher temp? i have no idea what to look for from here. i also have pluggs wires throttle clean and air filter replaced. and car is running smooth just needle shows hot.

here is a picture of the needle when the fans start to kick in. any help would be highly appreciated.

Originally Posted by Rico

What type of coolant are you using now?

I switched from Dex-cool to regular antifreeze. i do change the coolant every year to a year and a half.

Originally Posted by Fivefingerdeathpunch

Sounds perfectly normal to me.

Fans come on at 212 and 226.

I think the half way mark on the 04+ cars is right around 200ish.

Heat soaking in traffic is what the 3800 does best, if all the air has been blead from the cooling system and it doesnt overheat you are fine.

i will do another coolant system bleed in a few days and test it out.
so is it normal for the needle to fluctuate from the mark in the picture to the half mark when the fans turn on and back to that higher point? i thought it was too much fluctuation

Originally Posted by Rico

Did you flush the system really well when you went to the regular coolant?

yes i filled water and ran till the tstat opens and drained. did that about 5-6 times before switching to regular coolant.

So unzip2000, did you get this sorted out? What was the solution?

Thats perfectly normal. As long as your fans are coming on... you have nothing to worry about unless it hits the obvious red zone. Get a 160 degree thermostat.. runs cooler.. but may trigger a light for being too cool. Also in the winter your car will never heat up.. just be careful

Useless response only to boost up your total number of posts.

Originally Posted by stocker

So unzip2000, did you get this sorted out? What was the solution?

Sorry for the late reply. Yes i did figure it out. My radiator vents were clogged. due to mileage and ****ty dexcool I went ahead and changed my Radiator, Rad cap, and also had to change the Temp sensor which failed again, so got one from dealers. Radiator is 3rd party brand for OE specs everything else i bought OEM parts. Did a full system diagnostic fans kick in around 212-214 temp shows just a hint above half. Car runs great now. I have about 85k now.

Originally Posted by nos4blood70

160 is way too cold and not necessary for a N/A 3800. Get a 180 with fans tuned to suit it if really bothers you.

FWIW, mine used to fluctuate in traffic as well.

Thanks for the reply. It still does fluctuate a little bit not like before. doesnt bother me now. All set now.

So I'm guessing you would strongly recommend removing dexcool from the system? I have 85k and dexcool is still in :/

Personal preference if you want to flush the entire system and refill with the regular green stuff. As long as you don't have any leaks in the system (internal or external) then refilling with Dex is just fine. It's when air is introduced to Dex that it starts to turn into brown goo. At 85K I would flush the system and refill with your choice of coolant, bleed the air and call it good. Also, since I don't know what year or model of car your drive I would suggest changing the LIM gaskets to the updated aluminum ones if you have a 97 to mid 04. They will leak eventually and could cost you a new motor if left unchecked.

I personally went with green coolant when I changed motors, and have green in my 95 Bonne as well. "Extended Life" coolant usually means most people think it's ok to not change it in 150K and then wonder why they are having issues, lol... Any type of coolant needs to be changed out on a regular basis IMHO.

Originally Posted by stocker

So I'm guessing you would strongly recommend removing dexcool from the system? I have 85k and dexcool is still in :/

Its totally personal preference. From what I read online dex cool gets rusty by time. Plus when i did my first coolant flush around 50k it had already begun to make deposits which looked like rusty deposits. so I swapped it out as I do regular changes every year to two.

Thanks fordman and unzip. I had my local shop "drain and refill" the coolant but I am almost certain it was not a full flush of the system. While owning the car since 30k miles ('08 base model) I have noticed that there is a fair amount of "gunk" in the system already so I will be tempted to completely flush the system and refill with green this spring. Any favorite how-to thread online you want to link me to? I know I have seen at least a couple on this site. Thanks guys!

Originally Posted by stocker

Thanks fordman and unzip. I had my local shop "drain and refill" the coolant but I am almost certain it was not a full flush of the system. While owning the car since 30k miles ('08 base model) I have noticed that there is a fair amount of "gunk" in the system already so I will be tempted to completely flush the system and refill with green this spring. Any favorite how-to thread online you want to link me to? I know I have seen at least a couple on this site. Thanks guys!

Stocker, I dropped you a message. Thanks