Low temp thermostat, coolant temp variation

So I fitted the above the weekend, and I have noticed that when driving the temp gauge gets close to 180, then is slowly drops around 15 degrees and goes back up, this cycles a few times. I presume that it�s the thermostat opening and closing as it is warming up. I never noticed this on the previous std thermostat (but then I probably wasn�t watching as closely). I seem to remember the std stat getting to just over 180 and staying there. Is this normal for the low temp stat?, I hope to take the car on a longer run to see if the temp stabilizes, as at the moment have only done short trips

That's my experience also and your explanation makes sense. I think that's also why it's better - the engine now spends more time (on avg) at the lower end of the temp range. I also noticed: - the SAI pump kicks in more frequently during the morning drive when car is not fully warmed up yet - the alternator voltage stays a little higher on avg (due to now a little lower engine temp. The alternator regulator compensates for temp - lower the temp, higher the voltage output). - no change in mpg the way I'm driving (mainly local)

I have low-temp tstat in my car and I experience the same thing.

Quotes source post: 10353091

You have a twisted definition of "better". The t-stat opening/closing means the engine experiences repeated expansion/contraction cycles, albeit small, but over time will probably have the head gaskets leaking. There's an increased in risk the t-stat will fail due to mechanical fatigue from the repeated cycling it goes through. The lower engine temp means the engine is being fed a richer mixture than it would be otherwise. While the car's mileage hasn't appeared to be affected -- though upon closer examination it will be found to have been affected -- the cooler engine with the richer mixture is generating a lot more unburned gas and water build up in the oil. To make matters worse since the engine runs cooler the oil will not get hot enough to boil this away and the build up will probably require more frequent oil/filters services. The SAI coming on while driving means the converters are cold and the engine controller concurrently with the SAI coming on is adding even more fuel so the injected air will burn post the combustion chambers and heat the converters to their necessary temperature. The alternator is working harder and this can only shorten its life. All to run the engine cooler where wear is increased. Better? I don't think so.

I have read several older arguments for and against using the lower temp T-stat but I wonder what the latest real world research / testing shows. Didn't JR even recommend the lower T-stat? Has anyone got the latest scoop?

Quotes source post: 10353178

Macster, your points are fair enough. However, engine wear also increases as temperature so the lower the average temp (up to some extent), the less the wear. I agree if you keep driving the car for short trips, the low temp thermostat may do more harm than good like you pointed out due to engine not fully warmed up. For me, my drive is long enough for the engine to reach nornmal temp so I'm not worried about that. The alternator at a higher voltage means it charges the battery faster. I always think the temperature compensation of the regulator is flawed on our cars since it's detecing the engine compartment temperature as opposed to the battery temperature. For a front engine car where the alternator and battery lie in the same compartment, that works well but not on our car. I always feel like our battery is a little undercharged compared to other cars because of this compensation. I've read both Hartech ( http://www.hartech.org/docs/buyers%2...20part%205.pdf ) and Jake's articles and happen to be a convert on this one at least... Oh btw, I'll do a UOA in 2k miles (first one after the low-temp thermostat install) so let's see if we see any trend there.

We are all using modern synthetic oils, right? The lower temp thing I think is more personal decision and psychologically more comforting to some people that the needle is closer to the middle. Gotta wonder how many people would be less inclined to do this if Porsche had calibrated their gauge to read more inline with traditional car gauges where middle means you're a-ok and not cold like the Porsche gauges. My $.02. I think if you hook up a water temp gauge to other cars besides Porsche, you'll find that 180deg isn't really that hot or dangerous in any way and is inline with where other cars are running more or less.

Quotes source post: 10353390

Alpine, it's a LOT more complicated than just the gauge reading. If you have time, I invite you to read the Hartech article (super long) in my post above but you can skip to page 40 for their reco.

It's funny how we pick apart Porsche(maybe a snowball witch hunt from the IMS?) and try to re-engineer everything. I'm sure there are some improvements that can be made and some of them could be detrimental. However I also see several high mileage examples that have done just fine driving it as is the way it came from Stuttgart. That's my story and I'm sticking to it. I don't like to have stained lips from drinking Kool-aid. Seems like the Porsche crowd sometimes wants that last 5-10% regardless just to have a peace of mind or some sense of security sometimes. I'll side with the Porsche engineers on this one as if it was something they really felt was wrong to begin with, they would've changed it on their later models at least with no additional cost to them(just different spec t-stat).

Alp, I think you would agree that the 996 is the worst car in the known universe since the Yugo, right? Just kidding.

Quotes source post: 10353587

HA

The reason for the standard high temp thermostat is because of emmisions, to control emmissions, you need a hot running engine. So the T stat decision is not made by Porsche for engine longevity, but to comply with emmissions. Hartech recommends the low temp stat because there is one situation, although it doesn't happen all the time, that can hurt your motor. The t stat is at the end of the cooling system loop, so that water that hits the stat has already gone through the radiators and is at its coldest. Therefore, there is a lag time between the coolant in the motor heating up and the opening of the stat. The hot coolant has to go through the entire sytem, through the radiators, before it hits the stat and opens it. So in a situation where you are cruising along on the freeway at high speed, low rpms, the cooling system is at its most efficient. The OEM stat is partialy closed or closed completely, which means the coolant is not going through the rads. Now, you downshift a couple of gears and really get on the throttle, the temperature in the head instantaneously goes up, and since the OEM stat is closed, or partially closed, cold coolant does not get to the head, which can lead to local overheating, especially in the cylinders furthest from the WP. If you have a stat that keeps the coolant 20+ degrees cooler in that situation, you have a cushion and also the stat opens earlier, which allows coolant that has gone through the rads to get to the head sooner. The cooler stat can't hurt anything, and it can help in some situations.

Quotes source post: 10353423

This isn't just a Porsche forum thing, there's similar sentiment in every forum for every vehicle with an enthusiast population. No car is perfect, and there is no better place to find (and blow out of proportion) those imperfections than on an internet forum.

Quotes source post: 10353628

This sounds all fine and dandy in theory and logically it makes sense. However it should be pointed out that the Hartech article also does not point to this as a common occurance. There are several 1-10% "what if" scenerios that we can tackle all day long on various parts of the car. And for the weak or weary, if changing all these little things helps them sleep better at night and avoid those unnecessary gray hairs or ulcers, so be it.(cough cough, KK) Nothing in life is guaranteed except death and taxes. Just drive it like you stole it, keep up regular maintenance, and enjoy the moment.

But whats really unusual and maybe a credit to Porsche's 996 coolant system design, is that my front rad fans rarely come on (with AC off of course) while stopped or driving yet I know they are working correctly. In fact, even though I am in a warm climate the cars temp never comes close to overheating. I have done a complete coolant system flush and run Pentosin but I must admit I am very impressed with the systems effeciency to rid itself of the engines heat. Maybe they got this part right? And, San you are correct. Pre super strict emission times, one of the first mods we did was a 160 T-stat.

Quotes source post: 10353673

C'mon man, there are guys that debate tires or oil all day long here too and on other forums. Those same guys drive like grandmas and usually never encounter cornering above 5/10's on the street yet complain they want more grip and comfort to boot. Don't forget that 80k mileage warranty.

Darrick, I have to disagree. Out of all the forums I am a member of or have been banned from (included for SP, and Alp), the only one that comes close to the amount of "my engine sucks" posts is the Ford 6.0L diesel forum. Man talk about a disaster of epic proportions. It almost makes the M96 NA look like a winner.

Quotes source post: 10353697

You need to go to the Ferrari Chat forums and look at pre-360 Modena threads there. You'll find that it even makes the Ford 6.0L diesels look somewhat reliable. Although you do not drive a Ferrari KK, you sure do treat yours like one. (inside Ferrari Joke that those owners would understand). I think you would actually be a perfect fit if you got an older Ferrari.

Quotes source post: 10353697

I'm aware, I also own a 6.0L Powerstroke F250. I apparently am a huge sucker for "terrible" engines.

Like Ferris Buellers dad, right? Your killing me.

Holy s@#$, Darrick, Im sorry bro. Lets hope it isnt one of the early ones. Im sure you are well aware of "removing the cab", EGR, heads, buy backs, lemon law, etc. etc. , lol. I remember those days all too well. And,, the 6.0's were just like the M96, you either got an incredibly reliable one or a ticking time bomb that explodes over and over and over. That brings back some memories, I still recall the "cabless" diesels all over the Ford shops.

Hmm, I've noticed none of those particular changes in my '02 C2 since I installed my low temp. It goes up to dead center 180 and stays there, except in stop & go on a warm day, where I am not using AC. Then it goes up to just touching the "0" of 180 until I get moving steady again and it goes back down. Alt volts are the same SAI behaves the same, etc. With the old T-stat in cold weather, I would get heat right away since the heater core is always in the loop, then blam! cold air from the heater when the t-stat opened. This does not happen, or is not at all noticeable with the new t-stat, so temp cycling was far worse with the old stat vs the new stat. The low temp stat should be I creasing efficiency by having more flow at a more constant temp vs the old stat. When you all say it is cycling, exactly from where to where on the gauge?

I need to check again but for me during some driving pattern, the temp needle will cycle narrowly between middle of "8" and straight up. The cycling is quite slow and subtle so unless you look at it all the time, it's difficult to notice it. Most of the time though it just goes up steadily to straight up position. It also depends on the weather. It tends to come down from the straight up position if the outside temp is lower (e.g., 60s).

Quotes source post: 10353759

2004 model with 185k miles on it now. Original head gasket, original EGR cooler, original turbo. On the 2nd or third EGR valve now, though (going to be doing the EGR delete sometime soon however, because I want to turn up the boost a bit). Only engine mod is a 4" turbo-back exhaust.

I had Flat6 replace the IMSB a year ago along with the water pump and Jake recommended the low temp thermostat. I did some other research before hand and felt comfortable with his recommendation so ask them to do. I haven't seen any major difference. No temperature fluctuations and SAI doesn't cycle on / off frequently. Needle just goes up to 180 and stays steady unless I'm in a lot of stop and go traffic then it creeps up.

Quotes source post: 10353423

I agree with you on this in general (yikes!), but sometimes Porsche's engineering design goals are more complex than 'we want the car to run as well as possible'. Noise and emission reg's are perfect examples of when sometimes undoing the factory engineering might have definitive advantage to owners... Perhaps Porsche used that particular thermostat because the higher temp and stability makes it easier to control emissions? Or because changing the engine operating temperature during the model cycle would have required additional compliance testing?

Quotes source post: 10353628

So...I drive mostly on the highway and (since the new hasn't worn off yet) not bashful about downshifting and stepping into the throttle. With the OEM thermostat in this vehicle, one could theorize, due to this instantaneous local overheating I would notice a (water) temperature difference on the guage...but I do not/have not. Sorry, I'm going to have to side with Macster on this one. I'm thouroughly satisfied knowing my oil is at proper operating temperature.

Quotes source post: 10354699

Production cars are always compromises due to variety of things but it is up to the individual if they want to change some of if. It doesn't necessarily make it any less of a car if you keep things "stock". In the case of emissions logic, I suppose I can remove my cats too so the car will perform better. Theories aside from a pure statistical perspective, I don't see changing out thermostats really having any detrimental effect whether our engines break down or not(track cars don't apply). As I've said before if you like seeing your needle closer to the middle, by all means do this mod.

If JR's most recent opinion is to use the 160 T-stat in a street car (not track use), I would strongly consider it if your changing the WP anyway. For me IDK because I do so much short trip, light use it might be a bad idea.

KK, are you trying to make it up to Jake for not using his IMS retrofit or solution?

Haha, if my budget allowed I would be buying a 3.8 JR prepped total solution and a lifetime supply of JG oil.

thats alot of oil when you change it every week

Quotes source posts: 10355476, 10355425

+996 ...or 200 miles whichever comes first. Fixed.

Quotes source post: 10353806

+996 I've been running the low temp stat (along with a new OEM Pump, Coolant etc) for over 2 years now. No change in fuel mileage, no SAI overactivity, no failed cats, no terrible explosions, no cels, no cracked heads, no loss in heat blah blah blah blah blah). The car runs great and the temp is nice an consistant. This is a daily driver that has seen 10 degrees (in the winter with snows on) and 100 degrees (in the dead of summer). If anyone thinks the gauge is accurate I have some land to sell you. Running a stat that opens sooner and that is fully open just a bit earlier than the OE stat is not the same as running without a stat........

Quotes source post: 10354702

As long as you are good with that, go for it. But if you are basing your logic on the above, your theory is way, way, off. The temperature is measured well after the rads, and is a slow to react indication, so even a FEW localized overheated spots would long be lost in the remaining 6 gallons of circulating coolant, by the time it reached the sensor. That was the whole point of the Hartech article. And as has been noted, appears to be actually more important on the MKIIs than MKIs, regardless of the increased airflow through the rads of the MKIIs. The damage occurs in seconds, and is cumulative, whereas the t-stat takes minutes to react. Look at the flow diagram, and it is obvious that the coolant temp IN the engine and at the oil cooler are far higher than the indicated on the dash. Just like how the coolant in the "entering" passages of the engine is far cooler than the "exiting" passages. Ideally, for best operation and longest life, the temp profile across the engine would be indentical, but that is, of course, impossible, so the best you can do is try to minimize the extremes. I plan to tape and insulate a thermocouple to the metal outlet cooling pipe and measure that temp, and get a definitive exit temp profile. Every car is a bit different, but on the MKIIs, I feel this is a win win improvement for longevity and oil temp control. The oil is plenty hot enough for the engine, no where near running too cool, in any sense. A 20 degree lower opening T-stat in the 996, because of its location before the engine, instead of after like on most cars, MAYBE gives you an average drop in overall coolant temp of 8 degrees. What it does give, is overall increased flow through the engine at normal operation. Naturally, I am NOT saying that all engines are doomed, or Porsche engineers didn't know what they were doing, yada, yada, yada. Only that real 996 engine professionals, with far more experience that everyone on these forums combined, have indeed noted and measured the scuffing, and localized hot spots on SOME of these engines, and how close to the edge the other engines are, no one may ever know. I prefer to keep my engine farther from that edge with this simple, effective improvement.

These are the same people that have something to sell you. OTOH, if it came from an independent source with nothing to gain and the statistics backed it up in raw hard numbers, I'd be more inclined to actually do something about it(not saying I don't believe the theory however). As for temps, one can get a rough idea with a $20 infrared temp gun these days, if anything to measure temp variations on the rubber hoses in different areas. Once again I'm certainly not preaching for one or the other. Individuals have to do what makes them comfortable and what makes sense to them. One can also debate on adding 3rd radiator for street applications too for manuals... There will always be things to nit pick over and that's what makes it great IMO. Being able to start a dialogue on these topics to address any perceived issues and /or compromises from the manufacturer and letting the individual decide if they want to address them based on their priorities, budget, comfort, and other constraints.

+1..right on! Agree with you 100%. Just an informative dialogue. I see it as, them not selling anything, or they wouldn't make the articles available. It's not like the M96 engine is known for its bullet proof cooling, though, right?

[QUOTE=alpine003;10353423]It's funny how we pick apart Porsche(maybe a snowball witch hunt from the IMS?) and try to re-engineer everything. I'm sure there are some improvements that can be made and some of them could be detrimental. However I also see several high mileage examples that have done just fine driving it as is the way it came from Stuttgart. That's my story and I'm sticking to it. I don't like to have stained lips from drinking Kool-aid. Seems like the Porsche crowd sometimes wants that last 5-10% regardless just to have a peace of mind or some sense of security sometimes. I'll side with the Porsche engineers on this one as if it was something they really felt was wrong to begin with, they would've changed it on their later models at least with no additional cost to them(just different spec t-stat).[/ QUOTE] Think so? 997 temp gauge.

I may be wrong but I thought the GT3 and later 997's have a lower temp stat as standard

Quotes source post: 10358932

The way I see it and I'm not expecting to have everyone agree with me, is that there are always things that can be improved and things that "might" fail in situations or under certain circumstances with any given part. Often times things can get cloudy in how things are either interpreted or might get communicated in the process. During that, it begs the question on whether something is often really "needed" or "required" in actuality for all practical intents and purposes. My wife for example gets her teeth cleaned and examined at least twice a year. I on the other hand haven't been to a dentist in 15 years and I have all my teeth still. I think you will find debates even among mechanics if somehow we can all get all master techs together on this and many topics. But the reality is that many bricks and mortars type mechanics don't really get to voice their opinion to the world since they are not on the internet, hence the cloudy part that I was referring to. One thing for sure, I think people should do things that make them comfortable regardless of what may by needed or not. That is the point I was trying to make.

Quotes source post: 10358986

I'm having a lot temp t-stat installed now. So it might be worse for the engine in the long run? What sort of t-stat are used in the Cup Cars? Seems like I can deal with the need for more frequently oil changes. That's within my control. High temp engine wear less so. p.s. Low temp t-stat is sold on LNE's website. I'm sure one of their guys will chime in at some point. Phew....for a second there at 5 years I thought I was the national record-holder for longest without a dentis's visit. In my defense, I only brush with down strokes, use a tongue brush, antiseptic wash and finish with a flouride rinse. Never drink coffee or smoke. Need to work on the flossing habit...

Quotes source post: 10358971

Those were different engines with different cooling needs so not sure you can compare apples to oranges. Porsche hasn't been shy of sending out TSB's for all sorts of things. If this was really an issue, I'm sure we would've seen a TSB on it.

Quotes source post: 10359011

That's the million dollar question, what constitutes a "high" temp within the context of this engine in particular? Engine hot spot theory seem valid for earlier coolant flow to reduce but how many premature failures have we seen or are going to see from the results of it?

well that's total failure, pretty smalll sliver of the whole for sure. But there must be other issues that can come up with running at high ER temp. particualrly for a car that's often driven in an urban setting and sits idling in traffic on a daily basis.

I bet the air-cooled guys are laughing at us right now.

in between wiping up their oil leaks

Cha Ching! Good one!

Quotes source post: 10359073

That's REALLY apples and watermelons..... I find it funny that we used to see a whole lot of "everyone needs a 3rd rad and manual switch on the rad fans because they run too hot" and "a cooler t-stat does nothing" to this thread. Can't take any of this too seriously. BTW, the low temp Tstat from Pelican is WAY less expensive than the exact same one LNE sells.

Yeah, but has the tstat from Pelican parts been christened by Jake Raby himself and baptized in a pool of DT-40? I think not.

Quotes source post: 10359073

not lauhing... too busy worrying about mileage depreciation to be driving.