For those of you following along at home, I have a '97 SE that I bought non-running, with a UIM failure, and a resulting cracked head and such. Got a new head, Dillon UIM, and all associated gaskets. At the time, I replaced the plugs, wires, t-stat (180), and all is well. Almost. It stays at about the 190 ish mark (maybe 1/4-1/8" to the left of 200, which is the only mark in the vicinity) most of the time. I can drive for a long time, and it stays there. In stop-and-go traffic - mostly stop - it climbs to 200, or just a hair over, maybe 1/16" past 200. This is with the A/C on, and the fans operating properly, but in 90 degree weather. I'm not concerned about the 200 degrees so much, it'* that my trans acts up when the engine heats up. The trans temp goes up with the coolant of course, with the trans cooler in the radiator. I did add an external trans cooler, which works great. My goal is to keep the temp from climbing up to that 200 mark. Also, I don't know that everything is up to par, as the '98 SE I'd been driving that has a stock thermostat goes up to just about the same mark on the gauge left of 200, and stays there no matter the kind of driving I'm doing. Basically, my trip home is 25 miles, with the first 10 of it being heavy traffic. After it heats up to the 200 mark, I'm able to get going at highway speed, but the temp doesn't come down for quite a while. Cooling system-wise, the radiator is clean, I put on a new water pump, and I have fresh coolant with a good mixture. The only thing I haven't tested that I can think of is the cap itself, but it looks good with a strong spring. Just for fun, I can cool it down with the heater on high, but that'* not much of a solution in this heat!

Did you drill the thermostat, also? If not, in that kind of heat, you may not notice a lot of difference on the temp gauge as the radiator cooling fans are still set to come on at the higher temperature. An aftermarket PCM that turns the fans on at a lower temperature would be a solution to that.

If you haven't drilled it yet, you may want to try a couple of 1/16 or so holes around the lip and see if that brings your temps down some. Cheaper than a PCM

No, I didn't drill the t-stat, and I probably should have. As far as the fan issue, it shouldn't have any effect either way with the A/C on, right? Both fans operate with the A/C on regardless of engine temp, or so I thought.

The A/C will start the fans. The compressor puts a large load on the engine, thus the need to have the fans run...so, that may not be as good of a test.

and remember the gagues can differ from car to car....the gages are a refrence at best

Depending on the outside air temp & the speed at which you are moving you won't see 180 degrees alot. In stop & go traffic you'll probably siting much closer to 200 since your pcm is programed with the stock fan points. You should try to drill your t-stat with 2-3 holes and it will help some.

Ed

Being an SE or naturally aspirated, the holes shouldn't be necessary.

I also had been running warmer than I wished. Picked up a 10 minute radiator flush by Zerek. While being a pain and taking an hour or two to complete, it'* very simple. Helped me tremendously.

I also tried to fill with distilled water as my area is known for very hard water.

Cost to flush.. about $20 with fresh coolant and the flush goop.

Brandon: I hope you ran a tube of the aluminum powder radiator sealer with water for a few days, as I tell my folks? I think those sleeves seal quite well with the JB weld, but it'* just a caution against pinhole leaks. If you did that, drained the water, and then installed coolant, I think you're OK.

As some here are saying, I agree that the coolant temp isn't excessive. However, if you have concerns, it sounds like a flush might be indicated.

Like many others here, i don't run Dexcool in my car. I've heard too many horror stories.

Just to add a few points -

I did run aluminum powder after the UIM replacement. It is not losing any coolant at all. I did flush and reverse flush through the block when I had everything apart. The coolant system is clean - I guess inadvertently running the fuel/oil mix through the coolant passages after the UIM failure may have helped clean it. The coolant really smelled of oil and gas so bad, I thought I could light the coolant on fire! When I removed the water pump, the pump itself and passages were very clean. On the other hand, the '98 I was driving had a nice load of DexMud in the coolant (!), yet maintained one temp whether I was driving at highway speed, or doing the stop-and-go in traffic. It reached it'* point, and didn't move. The '97, however, likes to fluxuate a little bit. I think what it'* doing is acceptable. However, I'm trying to band aid one thing (the acting up tranny when hot) with another (keeping the coolant below that 200 mark on the gauge, where it begins to act up). It really isn't that bad when it gets to 200, but it is noticeable.

About the fans...the stock turn-on temp shouldn't have any effect, as the fans are running when the A/C is on, which I can assure you it is 24/7 from now until about October. I come from the LT1 Caprices (having owned 7 of them), and they too have higher-than-they-should-be stock turn-on temps for the fans, at 220 primary, 232 secondary. However, when you turn the A/C on, that doesn't matter, because it turns the fans on for the condenser'* sake.

I guess I need to know if I need more coolant flow in stop-and-go traffic (drill the t-stat, etc) or more air flow over the radiator.

EDIT: Since the 200 degrees isn't REALLY the problem - it'* the corresponding rise in trans temp - I think I could attack this directly by adding a fan just to the trans cooler. I have an adjustable Derale fan switch with relay and wiring new in the box. All I'd need is a 10" fan, and I could get more air over that trans cooler. Hmmmmmmmm...

MORE...
I just checked my fan kit, and it has a 3/8" NPT fitting for the temp sensor. I believe the trans test port is a 1/4", so all I'll need is an adapter, and I can get the trans temp from there. I'll adjust it so the fan comes on around 190 or so. Now, I'm off to shop for a fan.