Regular Thermostat vs. Low Temperature Thermostat?
 

I'm about to change the coolant in my 2000 Boxster S (986) and may as well replace the water pump for a little preventative maintenance. I was also looking at the Low Temperature Thermostat which opens up 20 degrees earlier than the regular thermostat. I've not had a heating issue but why not go above and beyond if I can, right?

Has anyone done this and recommend it? Now that I'm at 10 years on this vehicle and doing the maintenance myself, I don't mind spending a little more now so it lasts that much longer.

Thanks.

I can highly recommend it; I installed one in my '02 S when they first came out and believe this is a modification everyone should consider. Repeating the facts as I know them, the factory t-stat begins to open at around 186 degrees F and is not fully open until coolant temps reach over 205 degrees! The LN stat opens at 160 degrees and is fully open before the factory t-stat even begins to open. This insures coolant temps stay (while the car is in motion) some 20 to 25 degrees cooler than stock, which translates to lower oil temperatures. Oil analysis has shown that oils breakdown at higher temps and is pretty well past useful life at 5 to 6 thousand miles.

My car runs cooler and I change my oil (Castrol Syntec 10W40) every 3000 miles, which is annually for me.

For more information, see LN Engineering Nickies The Original and Genuine CNC Billet Aluminum NSC-Plated Cylinders. This is a very inexpensive upgrade and most other factory models run low temp t-stats for the obvious benefits.

The most supported theory on the #6 cylinder failure (D-chunk) is its caused from to much heat on that back cylinder. Since #6 is the furthest cylinder from the water pump the coolant has travelled past every cylinder on the way to #6 and is to hot at that point. By installing a low temp like the one LN offers you will be reducing the risk of a very expensive D-chuck failure. I personally highly recommend the low temp for anyone with a 986 boxster.

We have discussed this on another board, but once the car is up to operating temperature, there is NO DIFFERENCE between having a low temp thermostat and a high temp one, once they are both open. It is radiators, not thermostats, that are responsible for coolant temperatures. The only difference is that the low temp opens sooner, which actually causes your engine to take longer to get up to operating temp, which is not necessarily a good thing.

So, it's really only the "interim" period that is different, when your coolant is between 160 and 190 degrees, and I have not seen any definitive issues that occur during that timeframe.

I disagree with your statement. The stock t-stat will remain open at 205 degrees allowing full coolant flow, whereas the low temp unit allows full flow at 184 degrees; big difference in my book. That's a twenty degree difference of coolant flowing through the radiators. I suggest you and the others from the "other" board re-examine the facts.

Operating temperature on most Boxsters is right about the middle of the zero in 180, which translates into around 195-200 degrees. At that point, the stock thermostat is mostly open, which means that coolant is flowing, and the engine is being cooled. If you are driving on the Interstate not running the A/C and not stressing the engine, operating temperature is a little lower, but the stock thermostat is still open. I am not debating your temperature ranges - I am sure they are close to accurate.

What I am saying is that all the low temp thermostat is buying you is an extended warmup period, which may or may not be good for your engine. I have not seen a lot of evidence that engines are particularly susceptible to issues during the warmup period, so I am not clear as to the benefits of extending that period. And, as I said above, it may not be particularly good
for your engine to be below operating temperature for a longer period of time.

Not only that, but by extending the warmup period, you are not allowing your engine to get up to operating temperature on short trips. If you drive your car regularly less than 15 minutes, it is not getting warm enough to burn off a lot of the water that has accumulated in the engine and exhaust, and that has been known to cause issues.

If you are worried about coolant temps during hard driving or tracking, get a third radiator - it will make a much bigger difference than adding the low temp thermostat.

Here is the full discussion - as you can see, there are people on both sides of the argument, but people like Lauren (who is a Porsche mechanic) tend to agree with my statements.

Steve is very correct. By the reasoning that people use about using a lower temp thermostat making a car run cooler, then why put a thermostat in at all? Free flow coolant all the time.

Simplifying Steve's point, thermostats affect warmup time, not operating temp.

If you want to be preventative on engine cooling, one of the most overlooked bits is cleaning out inbetween the condensors and radiators where all kinds of junk manages to get stuck. Its pretty easy to do as well.

The stock t-stat will restrict coolant flow when not fully open; in other words, it forces the coolant temperature to remain at the high 205 to 210 degree level. The low temp t-stat will remain fully open at temperatures as low as 184 degrees and not allow the temps to rise into the 200 degree range, unless the radiators are full or debris or the car is sitting in traffic with no airflow or fans running on the radiators.

I don't see your logic in why you think they are the same after warm-up?

This is just going to turn into another Oil or MM debate. The assumption Steve and I are making is that the vehicle runs hot enough that both thermostats will be open and cycling coolant through the radiators at operating temperature, and open = open. Internal head temps are approximately 300 degrees, maybe more, but well over that of the thermostats. One the engine temp is there (by vitrue of combustion), you should be flowing coolant all the time, depending on how efficient the heat transfer is from the block to the coolant. You are flowing the same temperature coolant through the system though, as both thermostats are open.

If you want to cool more, then you need to increase your cooling capability. At the very minimum if you are flowing coolant through the radiators at lower temps, then you need a lower temp fan switch to turn on the fans sooner, otherwise you are getting little cooling efficiency, expecially at low speeds where the extra cooling would be more warranted.

L&N vs stock T-stat hmmmm
 

Our 98 986 has 91k miles on it and this past spring I did a preemptive stirke and replaced the W/P. Along with the coolant swap I personally decided on the 160 deg t-stat. I would agree that it does in cooler weather warm up a bit slower it has helped with the blistering hot summer here in the NE this year. The other item I swaped out was the stock smaller oil cooler unit for the the 'bigger' 'S' type unit. I was able to buy one from DC Automotive used for under $100.00 that along with the new W/P the 160 deg t-stat have helped considerably with cooling this summer. Somewhere down the line I may opt for the 3rd rad but that is another project for another time. I would VERY VERY much suggest that at least once every 2 years you take off the front bumper and CLEAN out the junk that gets lodged between the A/C condensers and the rad's in the front bumbers and every year use a shop vac with a long hose attachment and vaccum all the loose debris and then hose it all out to clear out the dust.

Better cool motoring!

m2

Another way to consider is the factory could have put any temp thermostat on the car.. They chose the one they did for a reason. I understand we all have access to tons more data than the factory so it would make sense to replace it with one not specified for the car ;)

The factory did such a good job engineering the M96 platform, we should just forget the high number of engine failures and go blindly forward.

It's your car...believe as you wish.

I haven't tried it in my Boxster yet, but Water Wetter reduced (peak) temps at the track in my 944 turbo.

In the boxster I'm going with center radiator and a turbo'S' oil cooler.

Well, I talked with an automotive expert this evening, and I will admit that I was wrong - he said that an engine will run at about the temperature of the thermostat installed - if you install a lower temp thermostat, the engine will tend to run at a lower temperature.

However, he said that he would not recommend running engines at lower temperatures for a number of reasons. First, he said that modern engines are designed to run around 200 degrees - they are built such that the thermal expansion at that temperature is taken into account. If they run at lower temperature, they run richer, which hurts fuel economy and emissions. Also, he said most modern oils are made to run around 200 degrees - he said that most oils, until they get up to operating temperature, are somewhat thinner - they tend to collect water and gas, which is present until they get burned off at around 200 degrees. He said the major reason that engines have sludge issues is when they are run cooler than what they are designed to.

So, yes, you are correct that your engine runs cooler. However, the downsides are not worth it to me, as I would much rather run it as Porsche designed it and risk the small possibility of heat-related issues, rather than run it cooler, richer, and with the threat of sludging.

Steve, that may be under normal conditions where the radiators are sized large enough to keep the temps down. The thermostat regulates the temp.

Hot day, on the track.... definitely runs hotter than the thermostat. Those are the conditions when we try to improve cooling. I don't think a lower thermostat will help there.... ask your 'expert'

Can't speak for "before", as I haven't had the car that long, but I added a bottle of the Royal Purple Coolant Additive (Water Wetter if you will) and at Roebling Road, I was boiling brake fluid and the coolant temp was rock solid. Day was high 90's, heat index was 112. Was quite pleased. I did notice the same in my old 944 turbo as well, but it was a daily, so it was traffic where I noticed it.

I completely agree - my statement only referred to "normal" conditions - if you're running warmer than normal, it makes no difference which thermostat you have. As was stated above, if you're warm enough where the stock thermostat is open, it makes no difference.

I agree the lower temps will not burn off the water and fuel collected in the oil (the M96 lends itself to fuel contamination) which is why LN Engineering recommends using a higher quality oil than the factory fill and changing more frequently in the 5 to 6 thousand mile range.

PCA Chicago Region is very fortunate to have Charles Navarro of LN within our region and readily available for M96 engine discussions. I don't wish to "parrot" his remarks, but the data he and Jake Raby have collected over the years speak volumes to the issues these engines have. I wish to keep mine healthy and have made a number of changes over the years to protect my investment.

BTW, I'm glad to see participation on the Pelican Forum...Wayne has been good to us and I know he's trying to build an active community here.

Jake Raby is not too far north of me, and I am planning on running up there when my clutch gets low to do the IMS retrofit at the same time. While my Box is an early model, it also has a factory replacement engine, so I am not as worried about it.

The car has been rock solid for me though, so no complaints to date.

Re Jake
 

I hear tell it isn't a simple matter any more of "running up there" as he has a months long waiting list especially during the winter months where folks from up North want to ship their cars to him and get them back for the warmer months.

Make your appointments early....

Very true, but as my clutch is working strong, I am a ways from that point as well. :)

Good point, Mike
We work from an appointment only basis. Our primary work is M96 engine development and engine production, service and IMSR procedures are done when we have openings.

The fall and winter are our crazy times of year and they fill up fast.

Charles at LN Engineering ran dyno tests on the car before and after the installation of the lower-temp thermostat, and he found a +5 HP change with the lower thermostat. He believes (and I tend to agree with him), that Porsche set the cars to run hotter so that they could boil water and other contaminants out of the oil in order to provide for longer oil life and less frequent changes (mandated by governments, etc.). I tend to believe that frequent oil changes, and the addition of the low temp thermostat is a positive upgrade for these cars.

Some other things to think about - the 3rd radiator. If you install the 3rd radiator, then the cooling effects won't be fully utilized until the thermostat opens up completely. The stock t-stat with the 3rd radiator will act to artificially inflate the operating temp of the engine because the t-stat will close back up when the coolant is cooled down below the opening point. Also important to consider are the cooling fans. Although the low-temp thermostat opens at 160 or so, the fans won't kick on until the temps get much higher. You can trick the car into putting the fans on earlier, but in most cases that is not necessary.

-Wayne

You might have the later-style (big external nut) IMS bearing then, which is non-replaceable.

-Wayne

My experience
 

Well, after all that great feedback from everyone on the boards, I decided to try the low temp thermostat. My experience thus far is that the temperature gauge simply doesn't peak past the zero in the 180 mark and come back down as it did before. It reaches operating temperature and maintains.

While moving the gauge will reach the 180 tick mark and remain steady. While in traffic it is a little higher between the zero and eight.

Other than that I've noticed no difference from my layman's point of view.

Thank you everyone who chimed in with the advice. I feel very safe with the advice on this forum!

Since the temps of the engine are lower, you want to make sure you increase your oil change frequency. I recommend no greater than 5,000 miles.

-Wayne

Oil and thickness
 

From what I have read, most oils are thicker when cold an thin out as temp goes up. Thats why in colder climates you use a thinner oil, if not good luck on trying to start your car. If your not tracking your car theres no need for a lower temp thermostat.

Wayne, Am I wrong in my belief that the enemy oil is heat? It seems to me, that the warmer/hotter and engine oil gets. It tends to break down faster. If that is true? Then why would it need to be changed more often when the enigne is running cooler?
Just my thoughts.
Randy

Drew, Heat is the enemy of these engines. If that wasn't so. There would be no need for a Boxster S oil cooler. The cooler they run. The longer they live. I have a S cooler here that is going on my none S car. Driving in traffic is harder on these things than about anything. And that's the same as any car on the road. If you're on the track? Air is moving. In traffic. Not so much.
Randy

+1 A difference of 20 degrees is not going to make a bit of difference to the life and effectiveness of a quality full synthetic oil on the high side. I agree with your mechanic. Especially bad for folks that do short trips and never really get out a run the cars up to temp for long.

When I replaced the 90k mile water pump I also installed the 160 deg t-stat along with the Boxster S type oil cooler. All 3 of these items combined have worked very well for me. When we are crusing the temp gauge rarely goes over the white 'tic' before the 180 mark and when in traffic in the summer months the needle is right at 12:00 high and goes back down as soon as the car is back in flowing air. The center rad is on my possible upgrade list but the car has 95k miles and seems to be running fine so I'm inclined to leave it as is.

Iii

That I know, but somebody posted oil is thinner til it gets up to temp, that is not true. It starts off thicker and thins as the engine warms up.

Probably one of the most misunderstood factors about multi-weight oil is do they actually appear thinner when cold then when hot. The short answer (unfortunately) is both yes and no as the result of the convoluted way tech types look at oil.

Straight 5 weight oil will have viscosity values at both low (say 40 degrees C) and high temps (say 100 degrees C). The hot temp viscosity will be lower than the cold temp by a considerable value, depending upon the measurement method applied. Same test on straight 30 weight oil will produce values that are higher at either temperature, a function of the polymer chemistry in the oil molecules. Nothing unexpected here.

Enter VI (viscosity index improvers). When added to the 5 weight oil, you still get the same low temperature viscosity, but when heated, you get the viscosity of the 30 weight oil at that temperature. Cold, the VI package allows the oil to drop to its base or “winter” weight (10 in a 10W-40 oil). As the oil begins to warm, the VI package modifies linkages across the polymer chains, which gives you the higher “hot” apparent viscosities of a heavier weight oil (until the VI package begins to degrade). Technically, it can be argued that “viscosity index” improvements are actually “reductions” in fluid thinning under increasing heat, but to the engine it is the apparent cold viscosity of thinner oil, but the viscosity of higher weight oil when hot.

In absolute terms, viscosity does go down with increasing temperatures; but the engine sees an apparent increase in viscosity (or oil weight) when compared to the colder starting temperature. All a mater of perspective……………

Question for JFP
 

I have a 97 986 133k on it, live in southern Cali, what oil would you use? Btw I dont track the car, but is driven daily and does see traffic.

I would stay with a 10W-40 such as Castrol Syntec (ACEA A3, B3, B4 rated) and plan on changing it in the 5-7K (max) mile range. As an adjunct, I would also suggest both the 160 degree stat and the "S" oil cooler, both of which will help to protect both the oil and the engine long term. While other may feel differently, we have been running 160 stats in several cars for a couple of years now, some of which see heavy use, others are garage queens. UoA’s on all of them say the oil is lasting longer, and there are absolutely no signs of increased water or fuel contamination; and no signs of any sludge build ups.

With the 160 stat, the engine is running around the high 170’s to low 180’s (compared to often well over 210 with the OEM stat), more than hot enough to burn off contaminants; the oil is also seeing lower temps as well (limited experience with two cars with oil temp capabilities say 20-25 degrees) which appears to help the oil “stay in grade” longer between changes. Not a bad thing…….

I appreciate JFP's knowledgable contributions to these forums, and am taking his advice on cooling system improvements, as I have followed his oil recommendations. All proven by in-service testing and UOAs.

I have my low-temp thermostat and "S" oil cooler on the way, along with a new water pump. Looking forward to putting them in in the next couple of weeks, and getting my extra 5 HP too!