docmirror

Yesterday I had to go out in the afternoon for some errands. It was a hot day, and the car was running great so I decided to keep track of the temp during the trip and snap some pics of the results. I put the thermo and center rad in back in May, and haven't stressed the car much since then. I also cleaned the rads, and the AC condensers at the time of installation.

When I left the house the OAT 100F, 41%RH, 29.96"Hg. As I got into the city, temp came up to 102 by the bank thermometer(usually accurate).

First pic, leaving town, where the thermo started to open. No AC use
Second pic, Cruising down the fwy out in the country. No AC use
Third pic, in town stop and go. This is about the hottest it got during the trip, AC on high, fans running.
Fourth pic, almost to destination, about 25 min driving in town, stop and go, full AC, OAT 103.

On the way home, the temp dropped back to the left of the '8' slowly, and stayed there for the remainder of the trip. I don't have a before to share, but one trip in early May with temps in the mid 90s similar traffic, the needle would be over to the right of the little bulb icon, and move near the gauge tick to the right of the '0' before coming down when moving. I didn't like that, and had some concerns about driving in Aug in TX.

Some of the gains can be attributed to rad and condenser cleaning certainly, but I'm sure the rad and thermo have provided great benefits to engine longevity.

Things I've mentioned before, but bear repeating. I love the cooler AC at the vents. It's a noticable change. The cooling fans come on less, or run at lower speed after the rad and thermo change. Gained a little improvement in oil pressure, and it's even better now that I changed to 5W-40. For anyone in hot climates I would encourage these two mods when cleaning rads.

Paul Waterloo

very interesting. With my low temperature LN thermostat I have noticed no changes in the dash needle, it goes as high as to the right of the "0" on the "180". I have yet to clean my radiators since I owned my car.

sparks259

My normal temp in my stock 2000, the needle is between the 8 and the 0 no matter how hot it is. The only time it ever goes higher is in bumper to bumper traffic.

WalterRohrl

Stock '02 here, seems to always be between the 8 and 0, maybe a hair further to the right if in heavy traffic on a hot day but not usually, and NEVER to the right of the 0. Cleaned my radiators a couple of years ago, there wasn't a huge amount of stuff in there but probably still worth doing as it's easy enough and sort of interesting to see how it's built.

RngTrtl

I never understood the lower temp thermostat install. I lived in Dallas for 4 years and I used to run the **** out of my n/a 996 and then idle in traffic and never got past the 0 of 180. I could see using one if you track the car maybe though.

5CHN3LL

^ By the time you've run the **** out of the car on any given day, there is no benefit to be derived from a low-temp t-stat.

I ran my 996 from sea level to 8,400 feet in ~87-degree weather yesterday... with the AC on. As long as your radiators are clean and functioning, the 996 doesn't overheat.

Same drive in the same weather in my Corvette, I run the heater on full blast the whole way up. It sucks.

docmirror

There's lots of 996 mods I don't understand, so I get that. My op-ed is no better and likely worse than a lot of others. Heat kills, and the 996 is particularly sensitive to thermal induced failures. So - about $400 total to help avoid a $16-20k problem. I considered it a good investment while I had the coolant out, and the rads removed. If you want to keep your rads and thermostat - you can keep your rads and thermostat.

This was the hottest I could possibly get it. This was the greatest stress I could put on the cooling system, and I like that it barely got above 180F. Better for the heads, oil, AC, bearings, etc.

perryinva

The smarter brains at Hartech recommend it. Good enough for me. Anecdotal "I never saw anything wrong temperature wise in the 3 years I owned my car" are fairly useless statements. Based that logic, there are no weak points on the car..we just keep them too long....

And if I could easily afford to only own a car never out of warranty, I would.

Macster

You really do not know what the coolant temperature was under your test conditions.

You should have used an OBD2 code reader/data viewer to view the coolant temperature in real time.

docmirror

The list of things I should have, and should do is - endless.

As for what I do know at this point is the temp of the coolant sensed at the engine coolant sensor is a good 15F and maybe a bit more than it was when I bought the car. I also know the oil pressure has seen a slight but noticeable rise(due to lower temp), the AC runs the fans less when on, and I seem, but cannot state with accuracy that my fuel economy is better. I attribute this to a slightly lower adiabatic temp in the intake allowing for a slightly better intake charge. But again - this is not well quantified.

Cuda911

I agree. Once the car is up to operating temp and the thermostat is open, what difference does it make what t-stat is in there?

Even so, I just put a low temp thermostat into my track Boxste' because I am having some overheating issues with it. I figure if it opens at a lower temp quicker, it may reduce heat build-up. But, this may be pure fantasy.

dporto

I'm about to install a center radiator in my '99 C4. AFAIK it's got a 180 degree thermostat in it. The standard full operating temp is the temp needle on the right side of the 8 in 180. In hot weather with AC on in traffic, the needle climbs to the left side/half of the 0 (never to center). It's never gotten past this point since I've been driving it (since Oct '14). Once I get the center rad mounted up and start driving the car again, I'll revisit this thread and post the difference...

Volkert

Read the article by Hartech. According to them, 3.4L do not have cooling issues; 3.6 and 3.8 do have, due to a change to the headgasket design then implemented.
Another note on the displayed temperature is that what you see is not what the engine experiences, especially on the 3.6&3.8...so while the temperature seems rocksteady, it actually is not....

Volkert

docmirror

Gonna hafta respectfully disagree with ya there sparky. The job of any thermostat is to regulate the flow of the coolant around the jacket of the engine. In some case, as I posted in this thread, I stressed the car to it's maximum, indicating that the t-stat in my case was fully open, and flow was only interrupted by the button and flange. But - full flow of the coolant isn't always or even often the case. In many case, particularly in cold weather ops the t-stat isn't fully open. In some northern countries, the t-stat may remain closed all the way, as the thermal delta between the engine and the surrounding air is enough to keep the engine from overheating.

Ever see a truck, or even a car with a piece of cardboard over the rad? There ya go. Too much dissipation to warm the coolant.

So what this means is that the cooling system will operate the engine at the temp of the t-stat(which I showed with pics above in the most stressed case). Because I added cooling capacity to the system, I could induce my t-stat to go from fully open to regulated state. This was also confirmed by noting the fans cycling as motion was enough to dissipate the heat just by normal air flow.

Now, 'heat' in the engine can go from ~1400F at the exhaust valve and seat, to likely below 180F at the base of the sump plate. So, measuring the temp of the 'engine' is a relative thing, and that's why I said that the temp sensed at the coolant sensor in the engine responded favorably. Of course - the temp of the exhaust valve and seat prolly didn't go down hardly at all.


But, here's the key for me. My oil temp went down, as I noted on the increased oil pressure after installing the t-stat and rad. The coolant temp in the engine went down, my fuel economy increased slightly indicating improvements in reduction of adiabatic heat loading. All these taken together tells me I'm comfy saying that the stress on the metals in 'the engine' have been reduced. Piston faces, cylinder liners, rod journals, crank journals, cam chains, guides, bearings are all seeing lower temps due to lower coolant circulation temps and lower oil temps. The thermal loads on the life fluids of the engine are being carried away sooner(or at a lower temp) than if I had the 183F t-stat in there.

That's my op-ed, and I stand by it. Lower temps are good, regulating at 160F is better for the whole engine(exh valve notwithstanding) rather than running it at 183F with the t-stat in full exchange mode, and reliance on the fans to keep it from overheating.

Cuda911

^^^^ Very Macster-like, but I'm waiting for the REAL Macster to chime in with his essay.