Why I installed a low temp thermostat.

[Flavor 987S]

Originally Posted by san rensho

Four bolts to change it out. 1/2 hour max.

Thank you. that's kinda what I thought (and was hoping to hear), since they "are already in there".

[Bala]

I just installed the Wahler replacing the original. They look similar and the Wahler seems of good quality. It took me maybe 25 minutes. That's because one bolt is hard to access and I did not have a swivel type ratchet. You will have to drain some coolant - about 1 gallon.

[bar10dah]

I'm fast approaching 75K miles. A mileage where some say is a good time to change out the water pump as preventive maintenance.

I'm leaning towards the 160F Wahler. How difficult is it to use the specialized tool to replace the thermostat into the original cover? Is it worth the trouble to save a few bucks? Seems to be only about $6. Or just get the thermostat/cover already put together?

UPDATE: Disregard. I was looking at the wrong listing. Appears fro Pelican, $70 for all three pieces; thermostat, cover, gasket. $69.50 for just the thermostat insert...

[kotto]

Originally Posted by bar10dah

I'm fast approaching 75K miles. A mileage where some say is a good time to change out the water pump as preventive maintenance.

I'm leaning towards the 160F Wahler. How difficult is it to use the specialized tool to replace the cleaning thermostat into the original cover? Is it worth the trouble to save a few bucks? Seems to be only about $6. Or just get the thermostat/cover already put together?

UPDATE: Disregard. I was looking at the wrong listing. Appears fro Pelican, $70 for all three pieces; thermostat, cover, gasket. $69.50 for just the thermostat insert...

Where did you see the listing? I myself am looking at grabbing a thermostat to somehow increase something with my car. Anyway, I think it would be best if the dealers are to install it for you.

[tranceatlantic]

I installed the LN low temp thermostat a few weeks ago. I noticed that the temp gauge seem to sit at the lower temperature for a while but then eventually moves back up to its previous normal temperature position (needle approx vertical on a 1999 986). I figured this was because once the thermostat is wide open the final running temperature will be dependent on the radiator design/size etc.

One word of warning though. If you do a coolant flush don't park your car on an inclined driveway with the back end point down the hill. The air vent for the system is at the rear but the radiator is at the front. I had an air bubble in my radiator, went auto-crossing and blew my boiled coolant all over the place. For those of you without PhDs in physics; air goes up.

[Bala]

Originally Posted by bar10dah

I'm fast approaching 75K miles. A mileage where some say is a good time to change out the water pump as preventive maintenance.

I'm leaning towards the 160F Wahler. How difficult is it to use the specialized tool to replace the thermostat into the original cover? Is it worth the trouble to save a few bucks? Seems to be only about $6. Or just get the thermostat/cover already put together?

UPDATE: Disregard. I was looking at the wrong listing. Appears fro Pelican, $70 for all three pieces; thermostat, cover, gasket. $69.50 for just the thermostat insert...

I installed the Wahler bought from Pelican. Absolutely no difference in engine temp between stock and the low temp one. Installation was a pretty simple tho.

[coolbreeze551]

Originally Posted by Bala

I installed the Wahler bought from Pelican. Absolutely no difference in engine temp between stock and the low temp one. Installation was a pretty simple tho.

I found the same thing ... What is up with that?

[Chuck W.]

Originally Posted by Bala

I installed the Wahler bought from Pelican. Absolutely no difference in engine temp between stock and the low temp one. Installation was a pretty simple tho.

Originally Posted by coolbreeze551

I found the same thing ... What is up with that?

Can someone answer this? TIA.

[Jaak]

It seems the T-stat opens earlier to get the coolant flowing earlier, that's all it does.

Nothing else changes with the temp as the car still generates the same amount of heat as before. The temp gague is slow to change unlike the ones the 944's have and show's an average over a short time span. My old 951 used to move up and down all the time ...

[pothole]

Originally Posted by Chuck W.

Can someone answer this? TIA.

I think people are looking at buffered gauges that won't show any changes unless they are very dramatic.

You need to be looking at the temp via either the aircon screen hack or better still via the OBD port.

The lower temp stat will make a difference to the normal operating temp as when the car is cruising at speed, it's the stat that determines the operating temp, if you had no stat at all the capacity of the rads to cool would lower the temps quite a bit at a constant cruise at say 60mph.

What I'm not clear on is why the stat would help keep things cool when the car is under heavy load etc. Once the stock stat is fully open (which happens at a much lower temp than when the car is heavily stressed in any case), there's no difference between the two stats. They are both just open.

And as far as I can tell, the reason to have the low temp stat is not reduce the temps at a constant cruise. It's to stop the coolant getting really, really hot. And it's not going to do that as both stats are full open long before the temps get really hot.

[thom4782]

Someone said it earlier: the thermostat trigger point only effects when the radiators begin to affect the temperature of the circulating coolant.

If the thermostat is closed, the coolant temperature of the coolant rises because the heat input from the engine is far greater than the loss. Essentially engine generated heat is lost directly from the engine block into the surrounding air. This is a very inefficient heat exchange.

Once the thermostat opens, the rate of heat loss in the coolant increases because the radiator exposes a large surface area of hot coolant directly to the lower temperature of the surrounding outside air. The rate of heat loss increases even further when air flows over the radiator as the car moves forward and refreshes the air surrounding the radiator with cooler air. This is why cars have radiator fans which increase the rate of heat loss when stopped in traffic.

It may be in boxster engines that the balance point between heat in from the engine and heat out from the radiators is above 160. If this is the case, then the low temperature thermostat has little effect on lowering the temperature gauge reading. If it does have an effect on the gauge reading, you would most likely notice it on cold winter days when the heat loss from the radiators is much greater because of the temperature difference between the coolant and outside air is much greater than on summer days.

I experienced this personally in college one frigid winter day as I drove my MGC from Connecticut to Ohio. The temperature gauge read Cold for the first couple of hours until the outside temperature warmed up to 20F. Then the gauge started to move about 1/3 up the scale toward Hot. There was some heat in the car from the heater. Late that day when the sunset and the outside temperature fell below 0F, the gauge fell back to Cold and I froze when the heater only blew cold air.

So the main reason cars have thermostats IMHO is to make sure the engines get up to an efficient operating temperature regardless of how cold it is outside and to make sure the heater warms the inside of the car. The radiators and the fans keep the coolant temperature from getting too high so the engine suffers less heat fatigue and doesn't allow the coolant to vaporize in the worst case. BTW: the coolant can remain a liquid at temperatures above the boiling point of water mainly because the coolant system is pressurized.

[Nimbus117]

I'm not convinced. It takes oil twice as long (as a guide) to get to temperature than the cooling system so I keep my revs low until then anyway. The only advantage I see is that the heater will warm the interior quicker in winter - except the car spends the cold months in the garage.

[kjc2050]

I installed a Wahler 160* thermostat this weekend (in addition to replacing the water pump and changing the coolant). The coolant is now at ~82*C when fully warmed up and the car is driven a moderate speeds. Prior to this change, the coolant was at ~88*C under the same conditions. Yeah, I know I changed the coolant in addition to switching to a low temp tstat; this was hardly a scientific experiment. But there's little doubt that the engine is running a bit (~10*F) cooler, and I doubt the coolant is responsible.

BTW, used the AirLift to fill the system. What a great product!!!! Took about 90 seconds to get the system to 25 lbs. vacuum; about 3-4 minutes to fill the system, and that included adding more coolant mix to the 5 gal bucket I was using. Worth every penny +++++.

[pothole]

Sorry, how was my hypothesis flawed. I clearly stated that the low temp car would start off from a lower position temperature wise.

In fact, nothing you said contradicats my point, which is that the low temp will reduce 'steady state' temps when driving, which is when you don't need to lower the temps, but not reduce temps when stuck in traffic.

At best, we disagree on how long it would take the low-temp stat car to catch up with the standard stat car when stuff in traffic.

In hot weather (which is again, when you are really looking for help with the temps), you are going to be putting on temp very fast with the car stationary or near stationary in traffic.

I would put my house on the low-temp stat car catching up within 10 mins max. From then on, you'll be in the same situation with both cars cycling fans and running at the same coolant and oil temps.

So if you got stuck in traffic for a n hour or two, the low temp stat car is going to have you running at high temp for fractionally less time. I can't see this is much advantage.

[JFP in PA]

Originally Posted by pothole

So if you got stuck in traffic for a n hour or two, the low temp stat car is going to have you running at high temp for fractionally less time. I can't see this is much advantage.

This is where your argument breaks down, you have chosen the only exceptional case where the two cars are the same, when stuck in heavy traffic, the rest of their existence, where they spend most of their life, is entirely different because they are running at different temperatures, both oil and coolant.

I don't know about where you live, but we don't spend our entire drive time stuck in slow or non moving traffic. And the difference on oil life and engine wear can bes significant

[pothole]

Originally Posted by JFP in PA

This is where your argument breaks down, you have chosen the only exceptional case where the two cars are the same, when stuck in heavy traffic, the rest of their existence, where they spend most of their life, is entirely different because they are running at different temperatures, both oil and coolant.

I don't know about where you live, but we don't spend our entire drive time stuck in slow or non moving traffic. And the difference on oil life and engine wear can bes significant

But that's the WHOLE point. The time when you want help with temps is when they are high.

With the standard stat, you are fine in normal driving. Temps are not an issue. What we want is something to prevent temps from getting too hot. Like heavy traffic.

But as soon as the temps start going up, the differences between the two stats fairly rapidly become moot.

So yes, most of the time in normal driving, the low temp stat means lower oil and coolant temps. But to no advantage because the standard car is not running very hot either!

[JFP in PA]

Originally Posted by pothole

But that's the WHOLE point. The time when you want help with temps is when they are high.

With the standard stat, you are fine in normal driving. Temps are not an issue. What we want is something to prevent temps from getting too hot. Like heavy traffic.

But as soon as the temps start going up, the differences between the two stats fairly rapidly become moot.

So yes, most of the time in normal driving, the low temp stat means lower oil and coolant temps. But to no advantage because the standard car is not running very hot either!

You don't see running coolant (and by default the oil) at 205+F all the time as running overly hot? Again, it is easy to observe the difference in how the oil feels about it as cars running the OEM stat show lower TBN values, and often have their oils "fall out of grade" at much lower mileage intervals than cars running the same oil but a lower temp stat. It is also interesting to note that Porsche's "max effort" cars, the GT2, GT3, and Turbos, all run 160F stats from the factory.

[pothole]

Originally Posted by JFP in PA

You don't see running coolant (and by default the oil) at 205+F all the time as running overly hot? Again, it is easy to observe the difference in how the oil feels about it as cars running the OEM stat show lower TBN values, and often have their oils "fall out of grade" at much lower mileage intervals than cars running the same oil but a lower temp stat. It is also interesting to note that Porsche's "max effort" cars, the GT2, GT3, and Turbos, all run 160F stats from the factory.

I'm metric when it comes to oil and coolant temp. My car runs at 88 or 89C steady state. That's totally fine.

What I don't like is how hot it can get when stressed or in traffic.

Moreover, the thing the low temp stat is advertised as being preventative for is bore scoring on some of the larger M97 engines, which is supposedly a problem related to very high temps and hot spots.

But I am at a loss as to how it does this since at higher temps, there's no difference between the two stats.

GT2/GT3/Turbo all have very different engines (well, did until the Mezger was dropped fairly reently). There are lots of things they have that may or may not be a good idea for the M96/7 engines.

[pothole]

Incidentally, the standard stat for bombproof 90's BMW straight sixes is 88 degrees.

It's a complicated topic. I'm yet to be convinced that a low temp stat is unambiguously a good thing.

Probably the ideal would be a stat that opened at 86 degrees like the factory stat, but opened fully at that temp. But even then, It's not going to make much difference as muc car only runs a few degrees higher than that normally.

[JFP in PA]

Originally Posted by pothole

Incidentally, the standard stat for bombproof 90's BMW straight sixes is 88 degrees.

It's a complicated topic. I'm yet to be convinced that a low temp stat is unambiguously a good thing.

Probably the ideal would be a stat that opened at 86 degrees like the factory stat, but opened fully at that temp. But even then, It's not going to make much difference as muc car only runs a few degrees higher than that normally.

Comparing the impact of coolant temperatures over time between an M96/97 to another make is an "apples to oranges" concept; their are entirely different animals due to the coolant system flow characteristics. The M96/97 has several widely known and accepted weaknesses, poor coolant flow in some areas is just one, but one that can be addressed by simply cooling the engine down somewhat.