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3800 Normal Operating Temp

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08 198 Champ

New member
Hi,

I just bought an 03 GP GT with 109K on it with the non supercharged 3800. The previous owner has all service records and really took good care of the care. I see this past fall the coolant was flushed, a new T-stat was installed and the system was pressure checked. I question though the coolant temp as shown by the gage. It looks like the T-stat doesn't open until the gage shows anywhere between 220-230. The temp drops down to one tick above 210 which I assume is 215 and will stay there for a couple minutes then jump back up to 220-225. Then it comes back down to 215 and does this back and forth for 10-15 minutes.

I have a 25 mile commute to work and I notice when I come back into town at a stoplight the temp will drop down to 210 then go back to 220 or so. For the most part, it stays at 220. Keep in mind I'm in WI and the temp here was 5 degrees F this morning. It acts the same way when its 40 degrees to.

I've checked the coolant and it is full and clean, the oil has no trace of antifreeze in it, I see no leaks, and I tried to bleed the cooling system with the bleeder on t stat housing. When bleeding, the engine was at temp, the t stat was open and the rad. cap was on. I tried it twice but got no bubbles. I still think there could be air trapped somewhere. I've also replaced the rad. cap. The heater works awesome also.

I talked to a guy at work today with a Bonneville that acts pretty similar. Does this sound normal for a 3800 or should I be concerned? BTW, the upper intake gasket was replaced about 20K miles ago but the LIM is the original from what the service records show. Let me know your thoughts.

I'm a first time poster on this site but have been reading it quite a bit lately.

Thanks, Bob
 


The thermostat appear to be working. It doesn't cost much to buy a 195 thermostat if you want to make sure it's running at correct temperature.
 
I might replace the t stat and see if it helps. It almost acts like it has a 210 or 215 degree stat in it (if they make one)....not a 195. Thanks for the replies.

Thanks, Bob
 


Fivefingerdeathpunch said:
Thats a bit too cold, unless your trying to hot lap it. It would run better at 195º, just saying.
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Just what the serif says the coolant is. I didn't touch the tstat do it may be open but the only one I have here id a 160. But I'm not too, worried about it since I need new fans

Sent from my Kindle Fire
 
Our engines come stock with a 195F thermostat.
Our pcm's come programmed to turn the low speed fan on at around 215F and then the high speed fan at about 228F.

The biggest gripe I had with my Bonne when I first got into 3800's was that the stinking temp on the highway was right at t stat temps and the minute I got to the end of the off ramp and sat at a light, 230F. You can have your fans programmed down to more reasonable/realistic temps. However our motors are most efficient at the temps you are seeing and it is very normal.
 
I agree the temps are "normal". But another thing is that the temp gauge on the dash is not usually very accurate. If you want a true reading, get a scanner and watch the temp in the PCM.
 
yeah very true about the temp gauge on the cluster not being accurate. Mine reads like 15F off, its crazy. you have to hook a scanner up to it.
 


BillBoost37 said:
Our engines come stock with a 195F thermostat.
Our pcm's come programmed to turn the low speed fan on at around 215F and then the high speed fan at about 228F.

The biggest gripe I had with my Bonne when I first got into 3800's was that the stinking temp on the highway was right at t stat temps and the minute I got to the end of the off ramp and sat at a light, 230F. You can have your fans programmed down to more reasonable/realistic temps. However our motors are most efficient at the temps you are seeing and it is very normal.
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Thanks for the information guys. This is my first 3800 and I'm not used to seeing the temp gage rise 3-4 ticks above 210 before the thermostat opens. I'm going to keep running it as is and keep an eye on it. It does run great and everything else with it seems fine.

Thanks again, Bob
 
Just an F.Y.I... I have had a communication with a GM mechanic in regards to the 3800 and talk about correct engine temp.
He stated that (and I'm paraphrasing) that temps above 210 - 215 will prompt the PCM to reduce timing by 3 to 4 degrees.
My 3800 rarely runs above 200 and the engine ssems to run its best at or slightly below.
 
BillBoost37 said:
Bob..that's were the fans kick on. Not the T stat. wink
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Do think the higher than normal (at least on the gage) readings could be caused by a seeping LIM? The oil and coolant are both clean but there seems to be some seepage around the manifold on the outside of the engine. Has anyone had any luck with Bars stop leak to help with the LIM that is seeping?
 
I'd recommend against using any kind of stop-leak in the oil passages of your engine. It might clot anywhere, like the pushrods or crank passages. If you have a LIM leak, just replace the LIM gasket. Promise that it ain't THAT hard. I even did it in-car with a couple buddies helping me. Including inj orings, LIM, HV3, coolant elbows, PCV, replace UIM, and replace plugs and wires, it took about 8 hours with a BUNCH of jokin around. Not that hard of a job.
 


ricksgpgtcolleen said:
I'd recommend against using any kind of stop-leak in the oil passages of your engine. It might clot anywhere, like the pushrods or crank passages. If you have a LIM leak, just replace the LIM gasket. Promise that it ain't THAT hard. I even did it in-car with a couple buddies helping me. Including inj orings, LIM, HV3, coolant elbows, PCV, replace UIM, and replace plugs and wires, it took about 8 hours with a BUNCH of jokin around. Not that hard of a job.
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I was thinking the Bars in the cooling system, not engine oil. Still have my doubts though
 
If you have an LIM leak, it's because you probably have the plastic framed gaskets.

The way these gaskets are collapsing into the ports, won't be fixed by any stop leak product.
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If you leave your car outside over night in sub freezing weather, then you start it and let it warm up at idle, you should notice the needle on your temperature gauge slowly increase and then stop. It should stop moving for a couple of minutes to maybe 5 minutes. When the needle stops your thermostat is opening. You probably have a 195 degree stat in there. If you let it continue running the needle should start increasing again. You can open the hood and observe the cooling fans. As soon as the fans come on check your temperature gauge. If you don't have your climate control system on, your cooling fans should have come on at low speed. Doing this test should give you an idea if you temperature gauge is accurate. There are differences in opinions on the ideal operating temperature range. A lot depends on your objectives and preference. I have a custom set up on my na 3800, so my normal range is 180 to 200. I think a 195 thermostat with fans coming on at full speed at 210 would be a very good set up also. It is important that your cooling system works well because if you run your engine too hot it can cause problems. I don't like running over 220 period. I run mine up to 210 occasionally just to heat up the cat.
 
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