Coolant temperature has never run so low.

Since my purchase in 2006, my '99 coupe has never run this cool, not even in winter. Just took a 25 mile spirited drive on back twisty roads and my coolant temp. never got over 80 degrees celsius(176 F). I had been postponing a water pump and thermostat(low temp. from Jake Raby) replacement and a coolant flush for awhile, but now that has been done and I no longer have 90-95 degree celsius temperatures. My WP and thermostat were original with 74k miles. There were no leaks or signs of WP failure, but I won't wait as long next time. I rarely drive my Porsche without displaying the coolant temperature, but I may now with much cooler operating temperatures.Nothing that earth shattering, but I thought I'd share my results.

Great data point in favor of LTT. Oddly ,there are some who are still skeptics about the LTT. Did you also clean the gap between the radiators and condensers ?Just wondering if that contributed to your positive result. To give others further encouragement to optimize the cooling system - see the Threads were the actual temperature of the hottest part of the system is contrasted to the gauge reading.

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Amazing the OP's 996 engine lasted 74K miles with that bad old factory T-Stat in there. And the LTT recommendation ignores the results of industry testing over the years that has found engine wear increases with a decrease in operating temperature and engine performance (and fuel economy) improve with an increase in operating temperature. But the OP's engine didn't blow in his test drive so the LTT science is settled then.

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Somebody touch a nerve?

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I have cleaned between condensers and radiators before, but not recently, and it's probably due. Headed for a quick round trip to Conn. at the end of this month, so I'll be able to rack up 350 mi. or so and monitor how hot the coolant temp.gets on the highway.

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Ouch! Guess I'll have to modify my 996 modes of failure and add increased engine wear to the list. Oh, and more trips to the gas station of course. Never claimed LTT science in my original post Mac, but feel free to draw your own conclusions. Where did I recommend a LTT?

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Evidently...

I have same results with my water pump and LN LTT swap. Put 2500 hot summer traffic commuting miles on since and its running great. No noticeable dif in fuel consumption. I will say the trans shifts on my TIP have gotten very noticeably smoother then when it was at temp with OE therm. Esp between into first, 2 to 3, and 3 down to 2. I am very happy with it so far.

Same here. Temperature settles during driving at 82C (LTT fully open) and with airco on will stay during city driving between 82-86C. With airco off it will go up obviously because then the fans are off. No LN thermostat so I believe it is a Wahler. Does the same as far as I can observe. With the location of the thermostat where it is the engine will be running at a somewhat higher temperature then indicated. Seems totally OK to me!

I did my LTT swap last week. I was constantly running at 186F at cruising and 197F in traffic (with fans on). Now i run 174F at cruising speed and 186F in heavy traffic with fans on. On days over 90+F i was running up to 204F in traffic and now it's at 192F.

I put in a LN LTT and new water pump last year, had no change in readings on the dash. I find this thread interesting and most who put in the LTT do not see any changes in readings, it just opens sooner.

Looks like we're all going to be suffering failing engines soon, right Mac? Nice to have some input. Thanks guys.

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I have a OBD2 scanner/guage installed and it gives digital readouts which is more precise then the dash guages. Before LTT the dash needle would sit between "8" and "0" (which is 186F on digital). Now it sits just a hair left of the line mark above the "8" (which is 174F on digital).

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I think his boxsters have given him a hinder-binder...... Great report Steve!

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I added the third radiator over the winter and just put the LTT and a new water pump in mine a couple weeks ago (MY99 3.4l). I've noticed very little if any difference in overall operating temp. (according to the dash gauge) i'll have to look closer at actual coolant temps in Durametric to tell if there's any real difference (I think I have a baseline from before I did the T-stat and waterpump). In my mind if the earlier opening t-stat smooths out any hot spots while the engine is warming up then it has done it's job.

LTT will do nothing for folks that have high temps due to not being able to exchange the heat properly (low airflow across rads, faulty fans, faulty pump, debris, scale, etc.). But those having that issue will have it regardless of LTT or not. So if all else is equal, might as well do LTT. That said, any temps below 95C, in my opinion, are pretty darn good, considering so many of us already have temp well above that number - ranging from 95-105 - so for those situations, LTT probably won't help all that much. Even folks who perform flushes, rad cleanings, water pump replacements and adding a 3rd rad don't always help either. Moral of the story: do what can to reduce the temps, and a LTT is just one of many items that appears to work just as well as any other attempt. Combinations are often what's required for some to make a dent in high temps

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The interesting part of a previous discussion on this subject was the potentially false security a precise + accurate temperature reading may give from the Coolant Temperature Sender. The concern was the location of the Temperature Sender vis a vis the hottest part of the coolant system. Ahsai delivered the useful concluding explanation iirc . There was also mention of improving the coolant routing .

its 65 degrees F in the summer where OP lives... He is the last person in the continental US that needs a LTT unless he is tracking it. Hell Id think hed need a HTT and a sweater.

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If the previous Threads on this subject are reviewed, the same misunderstandings recur. The reason for a LTT has little to do with ambient temperatures.The damage occurs before the OEM thermostat opens completely.And at 65 deg F ambient, the thermostat will eventually open - but too late. The LTT does not fix the defects in the design of the M96 Cooling System. It treats the symptoms, not the cause. Some expert M96 Forum Members have rectified some of these design defects in their rebuilt engines but I believe they still use an LTT.

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The question is whether or not Porsche's tstat is like other tstats, in that even a regular stat usually doesn't close completely. I mean, when it's cold outside, say 32F, the water in the rads is so cold, even a very tiny amount of fluid that escapes the regular themostat - which starts to open at 194F - still seems very safe, even if there are localized hot spots that are over 20F hotter in the hottest parts of the block.

If you read the Threads I mentioned it may help.Jake and Ahsai were notable contributors.I was not. The location of the cooling system design problem in the M96 is a a long way from the thermostat and the circulation in the problem area is sub-optimal. So the OEM thermostat does not respond soon enough to a localized spike in temperature - among other things. The LTT addresses only the cooling system design problem inside the engine. That is partially why we are not discussing more powerful fans for more airflow and related modifications. It is all in the previous Threads on this subject. These are not my ideas but yes , I did fit a LTT based on those discussions we had years ago when I rebuilt the engine.

Who knew there was so much controversy with a thermostat change(upgrade)? I'll be wary of any future posts concerning our 996s, and God forbid we install a non Porsche OEM device in our aged 911s. Didn't realize such complications existed.

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What you did for your 996 was good. That is clearly stated. The explanation of why it is good is just M96 geekdom stuff. Some people don't care to follow the geek stuff. That's O.K. The important part is to preserve the M96 engines - the rest of the car should last for ever. There is an interesting list of M96 preservation projects like the LTT elsewhere.

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Just had a nice drive today (German Autobahn) and can definitely conclude this is not true IF you are living in an area with moderate (65-75F) temperatures. The thermostate keeps the temperature nicely around 180F (with LTT installed) up to sustained driving speeds of 120MPH. When above 120MPH (120-150MPH) it crept up a bit to 185F. With the normal thermostat it would run above 200F. Now if you are living in a place where temperatures are normally higher (>90F?) I can imagine both thermostats quickly go to "fully open" state and you won't notice much of a difference except that the LTT just opens up earlier. I anyway think as it is designed that it makes sense to have always the airco on so the fans are always running at low speed. This greatly helps to keep temperature at reasonable levels. Also with a LTT without those fans running in city traffic temperatures will run up to 220F before the fans kick in.

If you think the temperature setting for switching the cooling fans on is an issue, I'll remind you of these ideas: https://rennlist.com/forums/996-foru...-fan-hack.html or https://www.renntech.org/forums/topi.../?_fromLogin=1 http://pedrosboard.com/read.php?7,4382,4424

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ditto

Paul gets it. The point of the LTT is not to make the temp gauge read lower - as discussed in previous threads. The CTS(for the temp gauge) is located(on the side of the console) quite far in the coolant circulation routing from the hot-spots of the engine so the gauge may be misleading in that regard. See post 369 Here for a color diagram of the coolant circulation and helpful comments by Jake: https://rennlist.com/forums/996-foru...engine-25.html

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The point of the LTT indeed is not to make the temp gauge read lower; because it can't. For that you'd need additional cooling capacity (additional radiator, fans running faster when driving slowly etc). However, in not too high ambient temperatures while driving I do see an effect that the average temperature is lower then with the normal thermostat. The LTT is fully opened at 82C (180F); if the temperature drops below 82C the LTT will react by closing a bit. Then the temperature goes up again to 82C etc. So it maintains the temperature at the fully open stage. As intended. Once the heat produced by the engine is above the capacity of the cooling system with LTT fully open the temperature starts to creep up until it finds a new balance. With the standard thermostat the engine will find its balance at a higher point. IIRC it is only fully open at 99C (210F) but normally it does not reach that point when driving normally. So the coolant flow is restricted by the thermostat during normal driving. My car is running with the original rads but new airco condensors. Maybe they let through significant more air then old ones? All the rest of the cooling system is in good condition including a new waterpump.

The steady state running is not the issue. Might be even that in the conditions you describe your engine will be running too cold or too much warm/cold/warm fluctuations. Especially in winter with colder ambient temps. But probably that is less problematic then running too hot initially. The LTT its main function is to open quick enough after a cold start.

The low temp unit opens sooner, and becomes fully open faster. The fully open faster part is why it can reduce operating temperatures, as it creates more cooling volume, being fully open. These have been tested in temperatures below -20F before they were ever sold to the public, over a decade ago. The units are proven- every engine I build receives one. This includes units fitted to vehicles with my engine in Canada. About 1/3 of our work is Canadian, about 1/2 of those are C4s and driven year round. The stock temperature thermostat had considerations when meeting the tests set forth by Federal Emissions Regulations. The engine needed the extra cooling system temperature to help keep the engine hotter for the "shed test" portion of the certifications. Lots goes into these vehicles aside from what works best for the engine.

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Thanks Jake. Your explanation makes sense. Appreciate your input.

Might be time for me to install one of these puppies...or at least clean my radiators.

I have a LTT and when it's in the 90's and I'm in stop and go traffic, my temperature gauge reads exactly the same if not just a tad bit higher, on the right side of the 0.

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What worried me was it was only 72 outside.

Same conditions, other car. Sitting in traffic, not going anywhere. Check the oil pressure as well, am running standard Mobil-1 oil. This is with rads cleaned, new airco condensors, fans running properly, new LTT, waterpump and coolant flush. 1998 C2 Coupe manual. Temperature indication earlier was like yours but then also one fan did not run in low speed mode due to a badly mounted relay. If I'd do a bit more driving to thoroughly warm up the car I would expect the oil pressure to drop a bit to 1.8-2.0 bar.

All those look normal to me. BTW, I tend to believe that the 2nd mark on the temperature display is around 110C.

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Agree, makes more sense that the 2nd mark is 110C.

It was -10F (-23C) today on cold start. After driving on the freeway for about 1/2 hour, my engine temps never got above 86C (187F). In fact, when I had some open road after the car was fully warmed, I went through some gears at high RPMs and saw my temps drop a few degrees (83C). To my knowledge, I have the stock thermostat. Is there something wrong with my thermostat, or do all 996s behave this way due to extreme cold air cooling the engine down significantly?

What you see happening is that upon promptly changing the rpm to a higher range the water pump spins faster which causes a sudden increased flow of much colder water from the radiators mixed with the hot coolant so more cold water enters the engine. Hence the sudden drop in temperature you see. After a while the thermostat readjusts to this new temperatures and finds a new 'equilibrium'. This new steady state could be some degrees off compared to befor as the thermostat does not have a linear range of operation. My coolant temperature reading once the engine is fully warmed up is 81-82�C (steady state) independent from ambient temperatures (-5�C or 30�C it does not make a significant difference). Of course it deviates from this equilibrium point some degrees depending on the way and how hard the car is driven, i.e. fast changing rpm's and driving speeds. Stop and go in summer will make temperature rise to 85-90�C but I do not consider this as a normal steady state condition as the water pump at these low rpm hardly pumps water and there is also hardly any driving wind for cooling. it always s around this temp. To me any coolant temp between 80-90�C is totally fine. The lower the better even! The reading is indicative as in some parts of the engine temperatures can be considerably higher.