92 Deg C Thermostat part number and source

watercop

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Aug 13, 2002
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Clay County, FL
Comments on the Acetone thread and a good mpg result from raising the t-stat on my Ford causes me to want to try one.

I checked a few of the sites suggested in BleachedBora's parts thread to no avail.

Does anyone know a part number and a source?

Thanks,

wc
 

rotarykid

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You can convert to * F and go with one of the standard on shelf models

I've never seen a thermostat with 92 * C stamped on it . But I have seen plenty of thermostats with 91 , 87 , & 83 * C stamped on them .

I think you are wanting a 91 * C = a 195 * F , 87 * C = aprox a 190 * F , 85 * C = a 185 * F , 83 * C = aprox a 180 * F thermostat .

Hope this helps .
 
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watercop

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Clay County, FL
I'm good to go on Deg C to Deg F conversion...

I'm simply curious to know whether the 92 C Thermostat mentioned in the acetone thread is available as a VW OEM part

I did a bit of internet research and it appears Stant part Nos 13379 and 45379 are dimensionally similar - I may try one - probably the 45379
 

rotarykid

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watercop said:
I'm simply curious to know whether the 92 C Thermostat mentioned in the acetone thread is available as a VW OEM part

I did a bit of internet research and it appears Stant part Nos 13379 and 45379 are dimensionally similar - I may try one - probably the 45379
I would bet that the thermostat in question is a 91 * C , not ever have I replaced a thermostat that was stamped 92 * C in any German car .

In all my years of working on VW diesels I've seen many 91 * C thermostats in turbodiesel VWs , Volvos , & Audis but never a thermostat with 92 * C stamped on it .

91 * C is the normal VW TurboDiesel thermostat in the south of the US . 87 * C is the normal in the diesel VWs , Audis , & Volvos that were non-turbo 1.5 , 1.6 , & 2.4 L 4 & 6 cylinder diesels over the last 30 years .

I've also seen 83 * C installed in older 1.6 & 1.5 L diesels but the engine didn't come with that thermostat 87 * C was installed from the factory .
 

watercop

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Clay County, FL
A quick test

I had an OEM 87 C unit handy following resolving my 16502 / 16512 errors, and before returning it to the dealer gave it a quick hot water test. It appeared to begin opening in the upper 180s, which approximates 87 C. At boiling it had an opening of 1/4" or so

I wasn't sure what the temperature rating of a t-stat meant - whether it begins opening at the labeled temp or is fully open. By this test it appears to be the beginning of opening.

Awhile back I replaced the stat in my powerstroke with a 203 F unit. I don't recall what it had before, possibly a 190. That truck has an aftermarket digital temp guage and its typical operating temp went from 177 to 191. The digital guage clearly indicates that the stat sticks a bit before first opening, allowing a temp of 199-201 before opening, at which point the temp drops to 190-191 in a matter of seconds. I think I picked up 0.5 mpg on a truck which yields low 20s, but we all know the futility of assigning mpg changes to particular events, owing to all the variables.

If I find the Stant 195, I'll try it in the saucepan before installing it.

There is a 205 Stant unit, p/n 13352 which has the same 2.125" flange diameter which implies it could be installed, but it lacks the secondary springloaded bottom flange, so I'm unsure what the consequences of that would be.
 

TDIJetta99

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03... Faster than yours =]
The 195* F thermostat is the one that the local parts stores around here list as the "correct" temp.. It makes me wonder what the one in my TDI is now.. For most of my drive, my temp according to vag-com stays at about 77-80 C. I noticed that the whole radiator starts to get warm when the temp reaches 55*C so I think my thermostat may be either opening a little too soon or possibly sticking open a little bit..

Usualy the rating on the thermostat is where it starts to open, it should be fully open around 10-15*F higher than the rating..
 
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Dangerous_Dan

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Thermostats

my car also wouldn't go above 80C so I think I either have the 71C thermostat I found on some parts sites or else mine is stuck. The thermostat I bought at Autozone has their part number 15479 and is a 91C thermostat. It goes in there tomorrow... with only G12 being added to make up any lost fluid...
 

Beetlebat

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Tenn
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Another factor we have in the older TDIs the coolant heaters. They are just like the starter glow plugs but shorter in length. I have noticed my temp varies more lately due to outside temps. If it's cool outside, the temp guage will actually move from standard operating temp to lower indication. I thought the thermostat may be failing on the open function, but I've never had a thermstat fail any way but closed, which usually meant overheating.
I know my plugs need replacing now, so I guess it's time to do it along with the belts and water pump. I know mine are failing because I got a CEL on the last 30*F morning at cold start.
98 Jetta TDI
 

watercop

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Clay County, FL
Installed 195 Deg F Stant 45379 today

The only issue I had was breaking off the two little prongs on the black plastic fitting that both retains the t-stat and attaches the radiator hose to the engine. Maybe Ididn't follow the 'Germish' Bentley directions to the letter. I went ahead and reinstalled the damaged plastic part - no sign of leaks or other problems

After a 25+ mile round trip Vag-Com now indicates my engine temp to be 93-94 Deg C, up from 88-89. This is in line with the increase in nominal T-stat rating. No change in dash temp indication behavior, but we all know what a farce the guage is!

I'll post some tank mpg results as the data becomes available
 

watercop

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Clay County, FL
you are welcome

A couple years ago one winter I fabricated a radiator hose clamp arrangement that let me artificially restrict coolant flow so as to drive coolant temp up quite a bit, 20-30 degrees. By tweaking the clamp I could get the dash guage to show 1 or 2 marks above the nearly meaningless 190, but not so high as to trigger a warning or the fans. I think Vag-Com showed temps in the 100-110 C range I don't recall observing a noticeable mpg gain, and I abandoned the test when weather warmed, but winter mpg is lower anyway and it is hard to isolate / attribute mpg changes to particular causes.


I would install the Stant 13352 205 Deg stat in a heartbeat were it not for its lack of the rear bypass plate. One poster earlier here said not having that causes the stat to oscillate. I wouldn't want to swing the coolant temp too fast and risk thermally shocking the engine.

I don't see an easy way to add the plate, either.

Intuitively, I figure that higher engine temps should improve both efficiency as well as emissions owing to presumably more complete fuel burn. Gassers are supposed to be more vulnerable to pre-ignition when engine temps climb but I wouldn't think that an issue with Diesels.

Years ago I remember enthusiasts at a major Ford Powerstroke site switching to something called Evans coolant. Advantages were said to be allowing coolant system to operate at zero pressure. I think they said the stuff could run at 300+ Deg F without boiling.

Come to think of it, I know of stuff called Dowtherm that remains liquid at 500-600 degrees and reasonable pressures - it is used in high temp industrial heat transfer operations.

At any rate, there must be metallurgical limits to progressively higher temperature operation - differential thermal expansion of various moving parts approaches dimensional tolerances and probably limits the ability to keep increasing engine temps. A mechanical engineer I am not...

To my knowledge 195+ degree T-stats are a relatively recent innovation (i.e. in the past decade or so) driven by both emissions and efficiency considerations. I wonder if progressively higher engine temps are being researched. We know synthetic oils can take quite a bit more heat...
 

Fix_Until_Broke

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Digging up an older thread here. In my quest for a faster engine warmup to reduce the effect of the cold start penalty, a higher temp thermostat crossed my mind.

Anyone that's tried this have any feedback on it?

Anyone find a 205 F thermostat or a way to make one work?
 

Brock_from_WI

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I don't know, now that I blocked everything up front, except the fresh air intake on the upper driver’s side, it warms up amazingly fast. Covering the oil cooler down on the lower passenger side made a noticeable difference. It is interesting to watch the intake temps slowly rise as the car warms up. It will also be interesting to see how cold it has to get before I don't hit 190 on my trip home any more. I am guessing around 25F. It was 35F with everything by the oil cooler blocked and 55F with the whole front opened.
 

nicklockard

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Bumping this up

My Scangauge II says my coolant temperature is 75C. It peaks at 76C under maximum loading. The coolant temperature sensor is new. The car is running 15 degrees too cold.

I'm going to boil test it to confirm before ordering a replacement, but is this: "Autozone part number 15479 and is a 91C thermostat" the correct part or is there an OEM version at 91C?
 
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RiceEater

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Watercop,
Really appreciate the sound theoretical and experimental physics you got going on. You obviously have a clear mind, a sharp pencil and started with a clean sheet of paper.

Cycling of thermostatically controlled valves is old problem real engineers have to deal with but I don't think it damages the engine as much as the life of the valve.

I totally support your ideas of 205F operating temperature or reverse flow coolant.
 

LanduytG

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99 NB 82 Westfalia Diesel
My 95 GM 6.5TD came with 195* stat. I thought I new more than the engineers and put in a 180*. After a couple of cold winters I decided to go to 205*. Going to the 205* increased my economy by almost 1 mpg. I should have listen to my dad who was a diesel mechanic all his life that the hot you can run a diesel the more power and economy you will get out of it. These run VW's run so eff. that I could see big stat making a difference.

Greg
 

03_01_TDI

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Denmark
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Na
The Honda Insight crowd has know for some time teh effects of blocking the radiator in cool weather.. Raditor was only the size of a notebook and a simple piece of cardboard would stop the airflow.
 

nicklockard

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Update

I switched out the t-stat to the NAPA 91C unit last night and test drove it. It reguates engine temp between 91-95C on a short hard test loop. I conlclude the old one was failed to open and the engine self regulated to between 72-77C. I am hopeful that economy will pick up, but then again I'm gettin 49.x mpg on the last tank. Removal and replacement guidance was found here in MoGolf's thread.

I also bumped the % of G12 up to 69%, and my A4 Winter Fronts came in today. The winter fronts speed warmups, and I am hopeful that the increased %G12 will also (it should have a small effect, in theory.)

(The formula is X = 2CY - C)| X is the liters to drain/replace with 100% G12, C is coolant system capacity, Y is the final G12 % you want to hit, in decimal form.)



Thank you WaterCop for posting this and the 91C part# :)
 

DPM

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opening temp for the stat on a Peugeot HDI is 83/ full opening 95c. Both of ours- in the Grand Vitara and in the 306- run at 73-75c according to Scangauge.
You've got to bear in mind that the sender and the T-stat are sensing in totally different locations...
 

watercop

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Aug 13, 2002
Location
Clay County, FL
Glad to have been able to assist

Does the old one look slightly open at rest? It doesn't take much opening to give the flow needed to cool our small engines, especially in winter.

Tstats are easy to test, easier perhaps if spouse is diverted or elsewhere:

Place in saucepan on stove, heat slowly, measure water temp when stat starts opening.

I find it odd that yours held in the 70s - I would have expected much lower temps at idle and generally a much wider variation proportional to engine load if it was failed partly open.
 

RiceEater

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It only takes a eyeball and less than a second to inspect most automotive type thermostatically controlled valves. Generally, that cursory inspection will show you that structural damage results in fail open and seal failure results in failing closed.
 

nicklockard

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Arizona
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SOLD 2010 Touareg Tdi w/factory Tow PCKG
To be honest, I have little to no experience with them...this is the second t-stat I've ever laid eyes on. Nothing physically obvious about its failure type...doesn't appear to be open, and its spring pressure seems adequate. Maybe it was just a bad part due to poor manufacturing (wrong spring constant) or perhaps, more likely, the last owner installed the wrong part#.:rolleyes:

However, I now feel justified for having purchased my Scangauge II, which felt at first like a trivial toy expense...because I would never have caught this w/o it! Also, since I changed the t-stat immediately after a fill up and calibration to the scangauge, I can compare this tank's fuel economy to last tank's (49.5mpg) and at least give one data point on the topic. The fuel economy went up 4% from scangauge's inital estimates based on this first fill up, so whatever I get for this tank will be multiplied by 0.96 and compared against the last tank with the lower temperature t-stat.

Also, aside from the temperature discussion, the Scangauge is teaching me to drive slowly and steadily...the payoff is nearly instantaneous...it's like a video game and somewhat addictive to try and maximize fuel economy :D

Back to topic: I will test that old t-stat in a pot of water and report observations.
 

RiceEater

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As a mechanical engineer I thought I would report what good mechanics already know especially as a report here is long overdue. As the water starts to boil you should actually see the thermostat instantaneously open at the rated temperature. This is because the valve is actuated by a eutectic salt. At the rated temperature the eutectic salt changes from the solid phase to the liquid phase. There is some expansion of the liquid phase and the valve should open slightly more with higher temperatures but not as much as when it first popped open when the eutectic salt changed from solid to liquid. This temperature response characteristic is important as the thermostat does not open until the coolant is at operating temperature whereupon it is open at a sufficient amount to allow cooling.

Seal failure is a common failure on automotive type thermostatically controlled valves and the eutectoid salt is lost as a result. In most engines water pump dynamic pressure and the mechanical spring tends to hold the valve closed and the thermostat fails closed. In the tdi the thermostat is placed such that the water pump “suction” tends to open the thermostat. If the small pressure bleed hole were obstructed over time the pressure differential would be greater possibly causing the thermostat to open sooner than desired.

As we know the BAD mechanics have reported that VW thermostats fail safe when a cursory inspection demonstrates that there is nothing unique about a VW thermostat. It was an even worse mechanic that critically looked at the thermostat, asked how it can fail safe and reported such on this forum. If these BAD mechanics have ever worked on a tdi they should have noticed a rather obvious difference in system architecture, yet they ignore this rather obvious difference and attribute the temperature response characteristic to a nonexistent unique VW thermostat. These BAD mechanics have also reported that thermostats open steadily from fully closed to fully open. Obviously if the valve did not fully open until the rated temperature most engines would never warm up. Definitely something delusional with what they see, what they do and what they say. Protect your valuable time and investment and make sure one of these mechanics (rotating child, fly by night, ancient poop, etc.) never gets a chance to lay a hand on your car.
 
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TDIJetta99

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03... Faster than yours =]
usually the rating is when it starts to open... a 195 thermostat should start to open at 195 and be fully open at 205-210.. They don't just snap open.. try it and see...
 
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