Cooling system mystery

[02WS6SSZ71]

Short background: Bought the car a couple months ago. Previous owner said the car had a 160 thermostat in it when he bought the car, which he removed because the engine temp barely went past the 1st line. He replaced the therm with a "stock" unit. When I test drove the car, it never approached what I consider to be a "normal" operating temp...I attributed this to the fans running non-stop due to an SES light. Now the SES light is remedied, but I am still looking at the same issues. I will add visuals to the story:
Driving down the road:
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24074926.jpg
Imediately after pulling in to my driveway
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24075713.jpg
Over the next 2 minutes at idle:
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24075843.jpg
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24075942.jpg
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24080031.jpg
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24080156.jpg
Once it reaches this temp, it cools back down to about 200, and then instantly starts to climb again:
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24080325.jpg
http://i600.photobucket.com/albums/tt86/02WS6SSZ71/2012-02-24080341.jpg
I know the temp gauge is not an exact representation of temp, but the fluctuations are just bizarrare to me. I have used an IR gauge, and the car gets up to about 225 when it is peaked out at idle, and then cools back off to 205ish. When going down the road, the car barely gets warm enough to put out any heat from the heater, regardless of ambient temp.
Any thoughts on what I may have going on would be greatly appreciated. My primary concern is keeping it cool in the summer with the a/c going. Thanks in advance for any suggestions.

[Fastbird]

Truthfully, take that gauge with a grain of salt. If you can get your hands on a real time scanner, look to see what the CTS in the water pump is saying as the CTS that feeds the dash gauge is in the head and subject to more variances than the one the computer references in the water pump.

Are the fans still running full time? Those temps while idling were normal. Driving down the road it should have gotten a little warmer, but see above. Now if you're not putting any heat out from the heater, that could very well be a.clogged heater core. My old bolt on car had the same gauge fluctuations as you but it still had good heat.

Posted from my Rezound

[02WS6SSZ71]

Truthfully, take that gauge with a grain of salt. If you can get your hands on a real time scanner, look to see what the CTS in the water pump is saying as the CTS that feeds the dash gauge is in the head and subject to more variances than the one the computer references in the water pump.

Are the fans still running full time? Those temps while idling were normal. Driving down the road it should have gotten a little warmer, but see above. Now if you're not putting any heat out from the heater, that could very well be a.clogged heater core. My old bolt on car had the same gauge fluctuations as you but it still had good heat.

Posted from my Rezound

Yeah, I knew not to put too much weight on the gauge, which is why I checked things with my IR temp gauge, and did so at the water pump. When you talk about a real-time scanner, are you talking like a Snap On type tool, or would my OBDII scan tool have that function? I know it will do freeze frame, but I'm really pretty ignorant about utilizing the features it has.

As far as the fans, I fixed the SES light, so they should be working properly...that being said, I can't see them to verify, and really don't ever hear them kick on or off. Regardless, the temp fluctuations are unchanged, SES light or not. My 1st thought was that the car was staying so cool due to the fans running full time, but if that were the case I wouldn't think it would ever get as hot as it seems to be. I guess I'm curious if the temp drop when it gets to around 225-230 is due to the t-stat opening (which I believe stock should be 180 degrees) or the fans (which I think come on at 225).

Regarding the heater core being plugged, I get heat when the car warms up idling. If the heater core were plugged, wouldn't you suspect that I would just not have heat period? Suppose that could depend on the extent of how clogged it was...

[02WS6SSZ71]

Well, I was going to wait until my work week was over, but I was just too curious since I was getting heat when the car was at warmer temps, but not at cooler temps going down the road...went ahead and flushed the heater core (and the rest of the cooling system after, and now I have pretty toasty air at all times...so much thanks for that advice.

Regarding my confusion about the temps fluctuating in exactly the same fashion when the SES light was on and after the SES was resolved...I was greated w/ a SES light this morning when I started the car to work on it...bad cat (luckily my UPS man should show up w/ headers/y on Wed). Despite the SES light being on, the fans still cycled on and off as they normally would. I have no idea as to the hx of the tune on the PCM, or if this is a function that can be deleted by a tuner. Regardless, I will be getting a fresh tune this week for the headers.

Based on your input and from LS1tech, and verifying temps were within normal range with my IR gun, I feel comfortable I can ignore my temp gauge unless it starts to head north of "normal." Thanks again for the input.

[AdamG]

I notice a lot of fluctuation in my gauge cluster in stop and go traffic as well when i actually did data monitoring with my scanner i noticed that the gauge was accurate at low ranges it tended to be off in the higher ranges. so when mine read 240ish it was more around 210-220ish my fans kicked on at around 210 and then take a few second for it to actually bring the temps back down.I bought an slp bypass though so i can switch between me taking control of the fans and then put them back to auto when i want to. I would like to keep the temps a little lower in traffic.

By the way i should add. I have a brand new radiator, the block was boiled out, and the heater core was flushed, brand new pump and thermostat I still get the same gauge fluctuation as yours.

One thing I noticed to is that no one has brought up is that different coolant level mixes will give you different levels of cooling. Im running a 50/50 mix. strait anti freeze does not properly cool your engine water does. The more water you add the better cooling effect you will get but you don't want to go crazy because the Anti freeze also lubricates you pump bearings and obviously protects your block from freezing in the winter.

[02WS6SSZ71]

Thanks for the input...I am going to look in to the fan override. I'm taking this car on the Power Tour this summer, which means quite a bit of stop and go, heavy traffic in 100 degree heat. I really don't like seeing the higher temps. Can't say for sure what was in it for coolant when I got it....the guy I bought it from said he had just flushed and filled it with Prestone. I know for sure now it has 50/50 Prestone/distilled water. I've often wondered how dilute you can get the antifreeze before you run in to lubrication risks with the pump...sure would be nice to run straight water in the summer.

[AdamG]

You can buy a additive that you can put in the water to lubricate the pump if you really wanted to run strait water. But I still wouldn't recommend doing it.

[BadBlackZee]

Another thing to think about...with a stock tune and the A/C off, the fans don't kick on until the 210* range. I live in Florida (90-100* temps in summer), and eons ago, when my car was stock, I would often have the car creep up past 210* when I didn't have the A/C on. With the A/C on (and with a stock tune) the PCM will force the fans on, so maybe you could try running it with the A/C on?

My car used to get pretty hot in stop and go traffic and no A/C. Once I started running A/C, the temps stabilized. Just food for thought. You could also have someone (or yourself) tune the car and lower the temps at which the fans kick on.