What temp to expect with a LN low temp t-stat?

So today i decided to do some preventative maintenance. I replaced the Water Pump, Thermostat, flushed all 6 gallons of coolant per Ahsai amazing write up and a new belt. Never had any cooling system issues in the past. Only replaced all this because my car is a 04 C4S with 66k and all original parts except non o.e. coolant. I ordered everything from the dealer (including 3 gallons of coolant) except the t-stat which was ordered from LN as a low temp. I also ordered the Driven coolant additive from LN. Everything went perfect. Before the temp gauge stayed between the 8 and 0 in 180. Now is no different. As with most car manufacturers i expected the gauge is a ballpark and not accurate. I hooked up my scanner and watched the temps from start up. With the A/C off the temp goes up to around 210 and the front fans kick on and eventually the decklid fan kicks on too as expected. So basicly the car is working just like its suppose to. The reason for the post is for some reason i expected lower temps and am not seeing it. What should i expect?

Glad to know my coolant flush diy helped. You will see the difference when you are driving the car. The temp gauge will stay closer to the left part of 12 o'clock assuming you are not stuck in traffic. If you just idle the engine till the fans come on, there is no difference. You should also find the temp gauge takes longer to go to 12 o'clock if you drive the car at cold start at cruising speed without much traffic.

It's not a daily driven car so it see's almost no stop and go. I take it to work every saturday (like today) which is 25 miles each way and its 22 miles of highway. I watched it on the way home and it stayed in the same spot between 8 and 0. Maybe next time i will bring my scanner for the drive to see the "real" temps. From what i noticed during warm up the notch by 180 represented anything from 145 to 215 on the scanner. Damn dummy gauges.

Has anyone had overheating problems with the stock thermostat?

Oh, and your write up on how to get all 6 gallons of coolant out should be in the Porsche service manual. You were not joking when you said you get every single drop of coolant. I used every drop of the 6 gallons of 50/50 mix plus maybe another 1/2 quart to top off. I have always used vacuum fill tools. No doubt they are the best way to make it so you don't have to waste time bleeding the system and worrying about air pockets.

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i live in hot as hell Central Florida and no issue here. I actually only did the low temp based of tons of post on rennlist talking about its a good idea.

Take a look at the one that came out. What was it rated at? Does that match the one you put in? I had significant improvement when I did my cooling sys refresh. I added the center rad, cleaned the rads well, and put in the 160F Tstat. Best mod I ever did for the car. Better oil pressure, lower temps, AC worked better, fuel consumption improved.

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the one i pulled said 83 degree's i assume celsius. Coverted is 180 F. I believe the LN is a 160f. I also pulled the bumper 6 months ago and cleaned the hell at of the rads and condensors.

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Which thermostat did you use? LN?

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Was not an LN. A generic 71C unit.

On my C2 I noticed the earlier opening of the T-stat on the gauge. The car ran a little cooler in moderate temperatures. In hot temperatures it did not seem to make much difference. I would assume b/c at that point the T-stat was open, regardless if it's temp range, and the limiting factor was then the radiators and dissipation of heat from the coolant. Worth noting that this is off the dash gauge, which is known to be inaccurate or "ball park" in nature.

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Seems to me the idea behind the Low Temperature Thermostat is open up +/- 20F sooner over the factory t-stat to mitigate damaging hot spots or to absorb so called waste heat. It's not intended to bring down the peak temps since full flow of coolant is already in process at that point? As others have mentioned, if you want better coolant properties at the higher range of temps, then a 3rd center radiator is your best option.

I did the exact same thing within 90 days of purchasing my 03 c4s. Before, the temp gauge would start to stray towards the other side of the �0� in the �180� mark during extended spirited drives in uber hot weather. While that was partially due to an inoperable radiator fan on the drivers side, after doing the cooling refresh as you did along with new tank, cap, hoses and fan, the temp now remains in the middle of the �8� no matter how long I drive, how hard I drive or the ambient temperature outside. I don�t think the low temp stat is designed to make it run a lot cooler, it�s just designed to intervene sooner to provide better cooling. Either way, I�m happy to report the system in my car works quite well and I�m satisfied with the maintenance I�ve put into the car in this respective area. I�d also like to say kudos to Asahi, for the write up as it was welcomed and used as part of my upgrade, cheers!

I'm toying with the idea of adding second decklid fan. Mainly because i recently replaced my C4S decklid with a turbo decklid. The turbo fan mounts in a bad position so i had to gut the plastic and make a custom one to install the fan in the right position. I could easily add the second fan off my C4S declid and have 2 functional fans. Most likely no reason to do so since it only turns on in stop an go traffic, but why not?

I am still stumped about the advantage of the low temp thermostat. Thermostats open and close based on temperature. It sounds, based on what users have said here, like the 996 cooling system is designed to stay around 180F so once the 160F thermostat opens, its going to stay open until the engine shuts down and cools off. If it opens sooner, the car will just take a bit longer to warm up. Is that the advantage? Or is the 160F thermostat supposed to keep the coolant temperature at 160F? Have 996's had a history of overheating that the 160F thermostat has fixed?

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No big mystery, just added insurance. In addition to my post above, this is from the LN site should put all in perspective: Did you know the factory thermostat doesn't start to even open until 186.8F and doesn't fully open until almost 210F? This causes hot spots inside your engine that can result in cracked heads and cylinder failures from overheating. Our 160F low temperature thermostat is not available from any other vendor and features a calibrated, German-made 160F thermostat. It is calibrated to allow thermostat opening a full 20-25F degrees earlier than the factory thermostat. That means that the the low temperature thermostat is designed to be fully open by 180-185F, allowing for full flow to the cooling system to maximize cooling potential. With high on-track water and oil temperatures, the 9A1 engine can use every bit of cooling it can get.

I think Jake Raby has stated this many times: Automotive thermostats aren't "on/off" switches that pop fully open at their target temperature. They start opening up earlier, and are supposed to be FULL OPEN by time they hit the target temp. So if you chose a random selection of NON-OEM thermostats (let's assume across the industry and across other makes/models of cars), you aren't going to get them starting to open at the same temperature, nor have the same flow rates at the same temperatures, until they are fully open (and you could expect different flow rates at full open based on how well the vendor adheres to the OEM design specs). So, getting a random thermostat to save money is asking for a random result in your cooling. Random is not good. People who say "but 160 thermostat at wide open is the same as a 180 at wide open" are ignoring the fact that your car could be 200+ in some areas of the block before the thermostat ever hits full open and starts cooling those hot-spots. At least that's how I recall Jake's responses. Yes, his recommended thermostat is expensive. Then again, we call complain about how expensive rebuilds are... (edited later .... I may have mistated the 180 as the target-full-open... regardless of whether that's a full-open or start-to-open number, the rest of it holds true)

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But it's not getting any more cooling. It's just opening sooner. That's what I don't get. Why does it matter that it take longer to warm up to 180F?

Not professing expertise. Just thinking out loud here, but it makes sense to me that a lower temp thermostat allows coolant to flow to other parts of the engine sooner, so they get the benefits of cooling sooner; prior to getting excessively hot and increasing risk of heat related damage.

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I can't speak for the true numbers in our 996's, but I can speak to the science: It's possible to generate the same amount of heat in 2 identical engines (same power generated, same heat that needs to be removed), and with a large enough radiator system, keep one cooling system at let's say X-degrees as measured at the thermostat and the other at X+20-degrees at the thermostat. In other words, if the radiotor(s) can radiate TONS of heat, and the water coming back from them was close to ambient, then the thermostat would shut down, slow the flow to achieve the X degree target. So YES your engine can run cooler with a lower thermostat, IF your radiators can shed enough heat.

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Coolant is already flowing to other parts of the engine. Keep in mind that the engine temperatures don't change instantaneously. They change over time. If someone has some test data showing these crazy high temperatures, I'd like to see it.

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True and a good point but my point is that it seems like our 996 engines run at about 180F regardless of the LN t-stat or the stock one. If that's true, why would opening the t-stat a minute or two sooner help? Of course running your coolant at 160F might create its own set of problems because the engine might not get hot enough to get moisture out of the oil.

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Understood. Our idiot gauges are notoriously unreliable for noting the true internal temperatures of the hottest parts of the engine, so I'd love to learn more as well.

I notice different on mine. Lets say that before was at the right of the 180 and now it is just at the left

Here's a few things I know(ok, no jokes here). I live most of the time in TX. TX is a hot environment. Heat is contributing to damaging engines, all kinds of engines, including the M96. When in traffic in Aug, my temp gauge would show approx 200F with the AC on. The red warning light for oil pressure would flicker once in a while at idle with all the fans running high. The voltmeter would dip when fans came on high. My AC had a hard time keeping the int cool(yes, pressures were tested ok). I redid my cooling system with 1. extensive rad/condenser cleaning, flushing rads. 2. New Pierburg WP. 3. Low temp 160F t-stat. 4. Added center radiator. 5. refill with 50/50 good coolant and distilled H2O. The difference in the car was night and day. In the worst traffic on 102F outside temp the gauge never got past the 8 in the 180 on the meter. The oil pressure at idle would be steady at 1.3bar. The AC would freeze me if left on high. My fuel economy improved. Hot starts were much easier, less cranking. Best - upgrade - ever. Low cost too, couple hundred bucks, about 8-10 hours of work.

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That's great information and quite an improvement. I'd guess however the the lower temperatures you're seeing are probably due to the center rad, cleaning the old rads and the new water pump. You just reminded me, I really have to take off my front bumper cover and clean my rads.

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Agreed. But - the other thing this change told me was that my gauge was useless for accurate temp info. My bet is that 200 indicated actually meant about 220, and that 180 indicated actually means 160 or so. The cost of the center rad and hoses was well worth the improvement. They didn't help during traffic driving, so the t-stat and cleaning did make a difference.

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I bought my 40th Anniversary Edition in November, so it hasn't seen a hot day yet here in Austin. The car has relatively new radiators, and the 40th comes with the slightly larger ones fro the C4. I'll consider the center radiator upgrade if needed, and at the same time replace the water pump and do an LN thermostat. Does anyone do additional oil cooling on these engines?

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Would you kindly link it? I have the 00s which may require this knowledge in the near future. I will be doing water pumps soon.

https://rennlist.com/forums/996-foru...pump-tips.html

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I don't know about oil cooler upgrades. That would be rather involved. Maybe some track guys, but I can say without question that extra cooling the water jacket had a good effect on the oil pressure, which tells me it was a bit more viscous both in traffic and on the highway. https://rennlist.com/forums/996-foru...with-pics.html

Here is what my gauge looks like after 15 miles on the highway at a constant 70mph. This is exactly where it was before my upgrades and now after as well. No change.

I put the old thermostat in boiling water and it doesn't open fully at 180F. It's slow in it's opening. The lowtemp seem to be more binary, at 170F it started to open and at 180F it was pretty open. This was in my kitchen, not very scientific. It also seems like my car runs cooler now at the track. However idle temp seems the same.

In sunny SoCal since preventive WP replacement at 31k mi 2004 AE car my front fans do not come on. Havent been on a hot summer, 405 FWY drive but still I never see 185. 180 is normal. Prior to the low T front fans would come on regularly.

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Good data points! This (to me) is telling us that by circulating more water earlier, the radiators are dissipating the same amount of heat at a lower radiator temp (low enough to not trigger the fans).

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Thermostats do go bad. It's just metal reacting to temperature. Your test is exactly what we did to the thermostats on our cars years ago. My mom never really liked seeing thermostats boiling on her stove .

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My mom and later my wife didn't like to see a carburetor boiling there either. #OldSkool

bplein - You�re in luck. The 40th Anniversary Editions came with the X51 power pack that includes the center radiator. The AEs also came with a duct after the center radiator to bring the airflow under the car.

Another data point: I have been through the whole thermostat debate on other marque websites. Based on Flat Six’s recommendation and LN’s reputation I forked out the dollars for an LN 160 degree thermostat. Per my experience, in most cases, one has to upgrade the other parts of the cooling system (fans and radiators) to take advantage of the lower thermostat temperature rating. I live in Las Vegas and the car typically runs higher than the stock 180 F unit so I figured there couldn’t be much harm. Test subject is a 99 Cabriolet with a 70K mile 2004 engine. Radiators are clean and water pump was changed along with the thermostat. I have done the fan modification and had both the engine and radiator fans were on. Ambient temperature was 58 degrees. Driving around town the temperature stayed at 81 C or 178 F. Freeway driving also resulted in 81C even pushing it going up a fairly steep grade. I then let the car idle in the garage. Temperature went to 95 C or 203 F. I raised the RPM up to 2000 to get some better flow and the temp went down to 87 C or 189 F. I wish I had run the test prior for comparison. I will test again this summer. I do have some summer data to compare to (225 F – 230 F). I suspect I will need a third radiator to see any real benefit in summer.

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That is not the steady state temp of stop-and-go traffic, which is closer to 12 o'clock. So you're not even close to the heat-shedding capacity of the system.

Isn't the point that the low temp thermostat lets the cooling system work earlier than the factory thermostat? At some given point: - With factory thermostat only 50% of the 180F water goes to radiator (made up number) - With low temp thermostat 100% of the 180F water goes to radiator (made up number)

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Yes

See post #677 here .

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The AEs do have the X51 power upgrade but no center radiator. They do have ducting in place to push the air back down under the car however. I just crawled under mine to double check. I've always read that there was no center radiator but you had me thinking twice about it (LOL)

Center rad is only on tip for trans cooling, and GT2/3 cars. I don't think it is on X51, unless a tip.

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Fan modification? Care to explain?

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so i guess in simple terms you are saying im in good shape?

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That's right. If your gauge stays at the right side of 12 o'clock even when the car is moving I would be worried.

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Wiring the fans to come on manually. The high speed fans don't come on until the water reaches 220 or something like that. Someone will chime in and advise of the actual temperature.

In my Mustang days, stock thermostat was 190. Recommendation was for a 180. A number of guys would run 160. Fuel injected cars would stay in enriched. Ode and burn gas and less power. Some guys complained car would run hot especially while driving at freeway speeds. Fine at idle or stuck in traffic. Theory was that the coolant flowed too fast through radiator and didn’t have enough time to cool. Flows slower in traffic. I had a stat seize open car would never warm up. Always wonder if the LN stat is too cool. What temps are guys getting with LN stat?

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i think their theory was broken! At a given ambient temperature and airflow, a radiator will dissipate MORE heat at a higher delta (difference) between the fluid temp and the air temp. If you can move water faster at the same inlet temp, then more of the radiator will be higher temp and therefor more heat transfer to the air. Not sure what year you are referring to with respect to Mustang years/models but back in the early mustang days you could remove the thermostat and while that was dumb from a warmup perspective it didn�t make your car run hot. Sounds like a bunch of non-technical folks reaching for answers. Now there IS such a thing as running coolant too cold. But that�s not what you are commenting on.

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The 160F low temp thermostat is open fully by 185F. The factory thermostat doesn't start to open until 185F and isn't fully open until 210-215F. It's graduated in how it opens and the wax cartridge will expand and contract with coolant temperature. The temp gauge on the dash does not report actual temp except on early models.

"The temp gauge on the dash does not report actual temp except on early models." ^^^This is interesting. When you say "early models" - do you mean 996's? How early, '98? '99? Why did they move away from this (I imagine it was $)?

I added the third radiator and it didn't change where my temp gauge stopped at in stop and go traffic. I then added the LN low temp thermostat. My normal operating temp is slightly lower as read on the really inaccurate factory gauge. My commute is 52 miles daily, with 2/3 of that in stop and go traffic. The rest is 80MPH or slightly higher. Occasional bursts up to triple digits.(Thank you V1!)

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i would agree with this statement in not only 996's but most car manufacturers. GM actually had a TSB about this at one point. It went on to talk about Volt gauges. Customer had seen the gauge move around so much that the would come in thinking they had a problem when they did not. The gauge just reported actual voltage. To curb the complaints they make it so a particular spot on a gauge will be a range of voltage. My 04 C4S is exactly like that. When watching the temps on the gauge, it will show roughly 180. But yet actual scan data show temp just barely in the 150s after a cold start. Temp could go just over 200 and the gauge would be in nearly the same position.

Mine (build 2/98) showed 180-ish, actual temp was ~165. Showed ~200, actual temp ~215-220.

My car temp gauge during normal driving will always be just to the right of the 0 on the 180, now after the thermostat change is just crossing the 8, this is normal driving, on the track during DE event with 80F ambient temp it goes just a bit more pass the 0, more like strait up and down. Not sure if this is something to worry about or not, would third radiator help this?

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Thanks Charles. I guess I'm still curious about the real improvement with the low temp t-stat. It seems that most folks that switched are reporting about the same temperatures with the low temp as they had with the stock t-stat. That's not a bad thing because you need to get the coolant hot enough to boil moisture out of the oil.

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We are used to this. It's the number one question as most people just report what they see on the dash. In some cases, the radiators have never been cleaned from road debris and that actually is negatively affecting cooling, so that's the first thing we ask when troubleshooting cooling concerns.

Is the Pierburg water pump the same as OE?

Yes and no.....yes the part is. No the box it comes in isn't. 😁

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thank you for confirming my hunch

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Update. Ambient 102 today at time of drive. Temps hit 212F - 219F on the street and 219F - 225F on the highway. I think I need to upgrade the radiators and cooling fans in order to take advantage of the lower thermostat.

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Is it possible yours runs slightly hotter as a result of having a 2004 3.6 motor with a 1999 3.4 radiator? I just read a post in another thread that the Mk 2 headlight change was done to accommodate larger left & right radiators (that's why early mk1-era turbos came with mk2 headlights). I wouldn't think the 3.6 generates that much more heat, but tossing it out as food for thought since it sounds like the 99 had smaller radiators than the 3.6 was normally was used with.

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How are you measuring these temps? My �99 reports the dash and HVAC as 12-15F higher than what the DME sees from ODBII.

As the OP i will add my updated data.....since my install i added CSF aluminum radiators. My OE ones started to leak. Even during these hot as hell days we have had in central florida my driving temps are never that high. Most of the time they stay between 185 and 200. If i sit at a long light they may creep a little. Maybe i will see 200 to 205. Never above that. Guess my cooling system is as happy as it can be.

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DME / OBDII. Are the radiators on the 3.6 cars larger than the 3.4? I never thought about that.

My car with center rad and LT thermostat runs at pretty much the same temp as it always did. The only difference is that the T-stat opens sooner (so less chance of hot spots) and it definitely runs cooler on the highway/at highway speeds (due to center rad). Sitting in traffic, it's the same as it always was (left side to center of 0 in 180).

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Makes sense, as the limiting factor for high temps on this engine is airflow (that�s #1).

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The only way to improve the low speed performance of the radiators is to use an aftermarket fan controller to kick the fans on earlier. This is what I did in my 99 Boxster fitted with a 3.8. I also added a Cayenne v6 electric water pump (which the controller also runs) inline with the radiators so that the coolant still flows and fans are kept on until the coolant gets to the target temp. I did this back when I was tracking the hell out of the car to cool it down between sessions with multiple drivers.

I've seen a mod for the radiator shroud and wheel well, applies to earlier cars I think to replicate a later change by porsche , it's in the 101 projects book

My fans are turning on sooner. I have hard wired them to turn on immediately via a toggle switch. I thought most of these cars run hot like mine in stock configuration when the ambient gets over 100F?

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Has to do with coolant temp, not ambient. The exception is when you have the a/c on, that' triggers the fans to come on. They are dual speed though, so the DME has logic to control when and at what speed they come on.

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Yes I understand. I meant the cars coolant temp starts to run hot (hotter) when the ambient gets over 100. I thought most of the cars run the temps I am seeing when the ambient is over 100F. The temps I noted above are with the fans running at high speed the instant the car was started. I have cleaned the radiators and installed a new Pieburg water pump. I suspect I am going to have to increase air flow or radiator surface area to lower the temperature.

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When we build race cars, we replace the factory radiator bellows with fiberglass ones we make up. This maximizes the airflow to the radiator, then we cut out the fender liner and put in a screen to keep large particles of debris off the radiators. https://lnengineering.com/products/b...tor-ducts.html For street cars, we also put in a GT3 condenser delete for the a/c, which also improves airflow through one radiator, like the factory did on the 996 GT3: https://lnengineering.com/products/b...e-my06-12.html We also make a 981/911 version, as the a/c fittings are different from the earlier models.

Charles, I have observed that a stationary 99 996 such as mine, even with the high speed fans on high, the airflow hits the ground and some of it wraps around through the intake. So the proper routing that and airflow design that you are talking about probably does make a difference. And high speed fans on high probably move a lot more air at highway speeds than when the car is moving slowly. It�s interesting to note than 996 cup cars don�t actually have fans at all. I guess if you are driving a cup car, you had better be driving to win