Who made the original equipment thermostat?

(Update: I just noticed that if I look down the into the opening of the thermostat itself (not the hose end of the housing), you can see that it is marked 71C and 160F) When I got my car five years ago I had the IMS and thermostat replaced with LNE parts by a trusted indy who is also a key member of my local PCA chapter. I just replaced my water pump and thermostat. Looking at the thermostat that I removed, it is marked with "Motorad - Germany". There are no other markings on the thermostat to indicate a temperature. The housing is marked with "80" in concentric circles, which may or may not be significant. The housing is made by Wahler and has part number 996.106.121BR on it Since replacing the water pump (which was in perfect condition), the thermostat, and about 3 gallons of coolant/distilled water mix, I've notice that the car runs a bit cooler than before. The normal temperature had the needle between the 8 and the 0, sometimes more toward the 0 when in traffic. Now the the normal temp is between the 1 and the 8, occasionally going slightly past the 8. 1. Was I screwed by my indy? (No, he did what he said he did ) 2. Should a low temp thermostat lower the operating temperature, or is that more likely due to refreshing a lot of the coolant?

Low means low... You are ok. Got what you ordered and it is working. Happy camper time.

Everything else being equal, the lower temperature setting thermostat will open sooner to circulate the coolant, which in theory should keep everything running a little cooler.

I noticed the same when I did the same maintenance work. Drove to Vegas in 106F heat and the needle was sitting below the midline the entire time. Used to take longer to warm up since the tstat would open up earlier but that was fine.

Pump efficiency and Tstat set point may be better with the new parts.

Just as a point of reference, a 180 degree thermostat is original, a 160 degree thermostat is considered low temperature. I would say the one you replaced with the 80 on it was an 180 degree thermostat...not low temperature. I know we have argued this one to death on here, but a low temperature thermostat does not make the car run cooler. Once at full operating temperature, both a 180 and 160 degree thermostat will be wide open allowing for full flow to the radiators. Granted, a 160 will open sooner, and if your drive is short then it might appear to run cooler. Please note what I am saying..." at full operating temperature "

Quotes source post: 12685815

That is my understanding as well. I was surprised by the slight reduction. Update: I just noticed that if I look down the into the opening of the thermostat itself (not the hose end of the housing), I can see that it is marked "71C 160F", so I did get what I paid for. Does new coolant have better cooling properties than old coolant, or is the difference mostly in its antifreeze properties? I guess the new pump could be more efficient, but the old pump showed no signs of any issues. The fins were intact and pulley spun freely without any wobble.

Coolant gets tired as it ages and does not cool as well. That's why you're supposed to flush it every once in s while. Also a newer pump moves water more effectively.

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Joe, You are wrong when you say thermostat temp makes no difference. You are confusing "Full operating temp" with "Maximum cooling system capacity" I.E.: What will the "operating temp" be on a 30 degree day without a thermostat? How about "operating temp" on a 90 degree day? Will they be equal at 180 once the car reaches "Full operating temp"? What will that temp be in those scenarios? Will it be equal? Granted if the cooling system is totally inadequate the engine will reach a very high "Operating temp" and boil out the cooling fluid. How do manufacturers design their cooling systems to preclude this from happening. They design enough extra capacity into the system. How do they control the temp with the extra capacity? They put a regulating device in the system, the thermostat. This thermostat will not increase the heat shedding capacity of a the system only decrease it when it is partially open. That is why the cooling systems are designed with extra capacity.

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+996 If you still have your old coolant, you can always check the PH level with the test strips or voltmeter. Yes new coolant will have better cooling properties but will also less acidic properties that can damage your seals and such and prolong your cooling parts.

A good read on low temperature thermostats: http://www.tuneruniversity.com/blog/...the-advantage/ Because the engine is designed to run at an operating temperature higher than the thermostat opening temperature, once the engine is up to full operating temperature (usually between 185-210), and under load the thermostat is full open and it's opening temperature is irrelevant. No change to cooling system capacity...it is the same for either scenario.

Quotes source post: 12686344

That has always been my understanding from way back in the days when such information was available only in fact-checked, published books. I must say I have been quite puzzled by the statements of both Baz Hart and Jake Raby, two indisputably well-informed gentlemen, that a low-temp thermostat will keep these engines running at lower temperatures. Or maybe I am misunderstanding what they mean.

I think operating under "full load" is key. If you are operating under full load at operating temperature, it won't make much difference. TS is not an on or off thing; it can be partially open at times. LTTS will stay open longer improving coolant flow. Again, it depends on the driving condition.

First some facts (both supported by the article Joe posted and by my own experience): Low temp thermostat will make the coolant temp LOWER (as shown on in the cluster) when cruising on the highway or driving at moderate local traffic (but not traffic jam). Under the same conditions, the normal temp thermostat will open LESS than the low temp thermostat. As a result, lower coolant temp is achieved in the low temp thermostat engine. Both thermostats are partially OPEN albeit to different degrees. Low temp thermostat achieves the same coolant temp as the normal thermostat under stop and go traffic, prolonged uphill racing, etc. The reason is under these conditions, both thermostat will OPEN completely so the bottleneck is the heat shedding capacity of the system, which is a function of radiator size, ambient temperature, and natural air/radiator fan efficiency, etc. The cooling system has hit its limit so even if you remove the thermostat, the coolant temp stays the same (high). In real life we drive under or somewhere in between these extreme conditions. With the lower temp thermostat, on AVERAGE we will see a lower coolant temp so we have more heat shedding "headroom" in the cooling system to cope with sudden high load acceleration or some short term traffic jam. With lower coolant temp, the sudden heat generated by WOT can be dissipated more readily with the coolant with lower temperature. This is where the low temp thermostat will help.

^^^+1

Great explanation as usual Ashai. However in the OP's case, since he was already running a low temp tstat, one could attribute his condition to the new coolant possibly as to the reason why he seems to be running cooler now. Either that or maybe a more complete bleed where there are no air bubbles in the system after he changed out his tstat/wp/coolant.

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Agreed. Sorry my explanation was just trying to reconcile the apparently conflicting views of the low temp thermostat. It didn't address the improvement the OP saw after the thermostat (same low temp to low temp) and coolant change.

Quotes source posts: 12685815, 12686344, 12686434, 12686587, 12686684

You cannot ascertain what thermostat is in place from the thermostat housing, an alternative thermostat cartridge may have been fitted to the original housing. I f you consider that, with thermostat lift being equal, a 160f thermostat is fully open at 185f and a 180f thermostat is fully open at 210f then you will appreciate that the 160f thermostat is open wider at 185f than the 180f thermostat. This means that at that particular temperature more flow is going to the radiators with the LTT than the standard thermostat; hence more cooling is available. Only at temperatures greater than 210f is the standard thermostat providing the same degree of cooling as the LTT. If the LTT is not wide open it will provide increased flow, better cooling and lower temperature than the standard thermostat. Same temperature below 210f means that the LTT will be open wider that the standard thermostat and will provide more flow through the radiators, greater cooling and lower engine operating temperatures, From personal experience my 996 tt in Middle East temperatures always runs at between 80c and 95c (176f and 203f), so the the standard thermostat is never actually fully open. At normal operating temperatures the thermostat is not fully open, in my car I have never seen temperatures outside of the operating range of the thermostat. Fact; unless you exceed the 210f maximum opening condition of a standard thermostat, an LTT will provide a lower operating temperature. Agree pretty much for the most part, the only time when an LTT does not provide more effective cooling is when the coolant temperature exceeds 210f. The engine water pump is a vane rotating within a casing. Over time wear will occur to both the vane and the casing (negligible). Wear occurs wherever there is pressure or friction; the wear on the the vane over time may not be immediately visible but any increase in clearance between the vane and casing will result in reduced pump efficiency.

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Agreed if it is excessively worn, but in the OP's case, he stated that his original still looked new. It's ironic that the WP's that have the most robust vanes tend to suffer from seal failure first while the WP's that have the best reliable seals tend to suffer from worn vanes or broken ones. It always seems like it's one or the other.

Quotes source post: 12687007

Ah ok. I don't recall ever seeing my coolant temp guage go much above 175.