Now that we've been hitting 90+ degree days here in Chicago, I've noticed that while running my A/C, the temp. gradually makes it'* way up to 200 degrees (even with 160 stat and 168 fan on). Normally it operates at or around 170. Why so hot?

200 is really nothing to worry about, but just to be sure, have you checked your coolant level and integrity? wouldn't hurt to flush the coolant right about now so you'll be ready for some insane temps coming later this summer.

Purged flush & fill was done last summer. Levels are normal.

The heat is most likely because you don't have enough cooling capacity to cool further. Maybe a larger radiator, intense t stat?

160 stat (AutoZone).
168 fan on (PCM).

It'* only when I run A/C after 20 minutes above 90 degrees. Below 90 degrees, the temp stays down around 170-175. Do they make a larger radiator for my car? (Who?)

UPDATE: I checked my fluid levels and the over fill was low (almost empty), so I filled up. Hopefully, that does something. Also, in case anyone else has this happen, I noticed when I opened the hood that the positive battery terminal has melted the red plastic and was smoking. I called my family mechanic and he suggested to tighten the bolt. I guess a loose connection can cause high resistance. I turned the terminal about one full turn and ran car for ten minutes with everything on and didn't see it happen. Hopefully, that was the issue.

I doubt that was the issue with your temp, but that certainly is not a good thing as it is, good thing you caught that. But it wouldn't hurt to remove the melted boot and take all the connections apart and check for any corrosion and reinstall them with dielectric grease. Bad battery connections can cause quite a few false errors with these cars. Also, be sure to keep us updated on the temp if it gets a whole lot higher for no reason, but if you want it to stay below 200, you're definitely going to need a larger radiator to handle that engine and trans combo WITH the A/C on. Definitely not an easy task.

I would consider putting in a larger radiator. Are there major modifications that have to be done, or are there ones that fit in the same place as the factory? (I.E. - drop in)

EDIT: I found one on http://www.intense-racing.com/

Oversized Aluminum Radiator

Code: TRA-686
Shipping Weight: 15.00 pounds

APPLICATIONS:
1997-2004 Grand Prix with 3800 Series II engine
2000-2004 Impala with 3800 Series II/III engine
1998-2000 Lumina with 3800 Series II engine
1998-2004 Monte Carlo with 3800 Series II engine
1995-2004 Regal with 3800 Series II engine

You also have to remember that even with the fan and stat mods, your engine can still hit max normal temp if you're not getting the added air flow from moving or if its hot outside. The mods only lower the temps that the stat opens or the fans kick in, not the operating temp your engine can/will reach. It should just take it longer to get there when it does.

Odd that Bonneville isn't listed on the Intense site for the W body radiator. A bonneville is an H body and uses a different radiator. There are some early 90'* caddy'* that used the same size though.

On the T stat.. Intense sells the high flow and it does flow a lot more than the stock.

Before buying a new radiator.. consider cleaing yours our with a good hosing on the outside..if the fins are plugged, then you won't get cooling