Alternative Thermostat for the X

[fastfiat81]

I've been working on the cooling system of my X lately. I replaced the radiator with a MWB aluminum, water pump with a GMB stamped impeller and a new thermostat. Brought it up to temp at idle and all is working perfectly. Temp stabilizes just under 190F and the fan kicks on one tick above 190F. Revving the engine easily drops the temp below 190F. A long drive tomorrow will give the final results.

I researched here and elsewhere on the thermostats that will work in our cars. As we know the correct and OEM stats are NLA or very expensive. Various Ferraris use the same t-stat as ours. The original t-stats had a 56mm upper flange, 34mm bypass flange and a distance of 33mm between the two flanges per Ferrarichat.

All the replacement thermostats that are recommended have a 54mm upper flange, around 35mm bypass flange and a distance of 30-32mm between the flanges. They also have a smaller diameter opening for the coolant to flow through once up to temperature. Here are some measurements of t-stats that I have bought. All are 180F.

Stant Superstat 45378
54mm upper flange diameter
35mm bypass flange diameter
32mm between flanges
Opens up to 42mm at 212F+

MotoRad Napa 138
54mm upper flange diameter
35mm bypass flange diameter
30mm between flanges
Opens up to 41mm at 212F+

Wahler 4256.80D
54mm upper flange diameter
35mm bypass flange diameter
31mm between flanges
Opens up to 41mm at 212F+
Also has a larger opening for coolant flow
similar to OEM

My t-stat housing measurements are:
56mm opening diameter
38mm depth from recessed opening to bypass hole
4mm recessed depth for rubber gasket
25mm bypass opening diameter

One concern I have is the thermostat expanding enough to completely close off the bypass opening, thus allowing all the coolant to flow to the radiator. The rubber gasket is grooved to fit on the thermostat so the total distance the thermostat has to expand is 40mm to completely close the bypass opening (38mm housing depth + 2mm for the split rubber gasket). Now the tricky part. Subtracting the 2mm for the rubber gasket (half it's thickness) to each thermostat yields the following distance:

Stant superstat - (42mm - 2mm) =40mm
MotoRad - (41mm - 2mm) =39mm
Wahler - (41mm - 2mm) =39mm

Only the superstat expands enough to completely close off the bypass opening.

Another is the 54mm diameter of the t-stats. Not a major problem but it can move around in the gasket. The third concern is the size of the opening for coolant to pass (the jury is out on this one so it seems).

This is a long winded way to get to my point. A post on Ferrarichat mentions a common, easily purchased thermostat that has the characteristics of our OEM Savara. It is OEM on a 2006 Toyota Prius. 180F ~$15

Orielly Autoparts 4108
Advance Auto 14108

Both are MotoRad (at least around here they are). There is a Gates version out there, but I don't have a part number for it.

MotoRad 4108
56mm upper flange diameter
28mm bypass flange diameter
33mm between flanges
Opens up to 43mm at 212F+
Also has a larger opening for coolant flow
similar to OEM

It is stock in all aspects except for the bypass flange diameter (though it is still big enough). It expands more than enough to close the bypass opening, fits the housing and gasket perfectly and has the larger opening for coolant flow. I have it installed in my car and works like a charm so far. As I said before a test ride tomorrow will tell the tale.

Give it some thought. Give it a go. Or not. I understand I'm waaaaayyy deep in the weeds with respect to thermostats, but it has been a fun side diversion. All currently accepted thermostats work fine in our cars for sure, but my OCD just got the better of me. Maybe it will help someone in the future.

 

[Dr.Jeff]

Great info. I enjoy doing this type of research and seeing what can be found to improve things. Nice job.

I have a couple of thoughts on it.
The diameters of the upper and lower flanges are fine on any of them; they will cover the holes in the housing and that's all they need to do. I've found if you use a new rubber seal with the smaller diameter ones (54mm) then they don't move around. And you can easily get new rubber seals of the same style in the 54mm diameter (VW applications).
Also there are "high flow" versions of the replacement T-stats from MotoRad and possibly others. These have larger openings and should have as much flow as the stock one.
But the distance they open could be much more relevant as you say. That is the biggest potential benefit that I can see with the Prius item. Might be worth doing a little experiment with a housing and a couple stats to see how well they actually seal off the bypass.
One potential issue with the Prius T-stat (great find by the way) may be if it isn't available in optional temps. It could be available, but I don't know. That is something that's important to me due to the extreme climate where I'm living.

Keep us posted on your findings.

 

[Dr.Jeff]

Just took a peek at the referenced T-stat part numbers. The Stant number (14108) shows this application list:

LEXUS	GS300	1993-2005
LEXUS	IS300	2001-2005
LEXUS	SC300	1992-2000
MITSUBISHI	OUTLANDER	2019
MITSUBISHI	OUTLANDER PHEV	2019
MITSUBISHI	OUTLANDER SPORT	2019
MITSUBISHI	RVR	2019
SCION	IA	2016
SCION	XA	2004-2006
SCION	XB	2004-2006
TOYOTA	4RUNNER	1996-2000
TOYOTA	ECHO	2000-2005
TOYOTA	HIACE	2006-2014
TOYOTA	HILUX	2004-2014
TOYOTA	MR2 SPYDER	2004
TOYOTA	PREVIA	1991-1997
TOYOTA	PRIUS	2001-2009
TOYOTA	SUPRA	1993-1998
TOYOTA	T100	1994-1998
TOYOTA	TACOMA	1995-2010
TOYOTA	YARIS	2006-2010
TOYOTA	YARIS IA	2017-2018

Based on this list I looked under a couple of the vehicles and see some alternate MotoRad part numbers:
289170 = 170 degrees
289192 = 192 degrees
They are very close to the same dimensions but different temp values. The important distance of the 'depth' or 'bypass length' is identical. The flange diameters differ very slightly, but not enough to be an issue. So these should work.

Some other numbers:
Gates: 33798S (180 degree)
Stant: 46108 (180 degree "SuperStat")
MotoRad: 5298180 (180 degree "Ultrastat" - better quality and includes a "jiggler")
MotoRad: 7298180 (180 degree "Failsafe" - supposedly if it fails it will only do so in the 'open' position)

I don't see any "high flow" MotoRad units in this range.

 

[Ics19]

My t-stat housing measurements are: 56mm opening diameter

Guessing this is a typo, as pretty sure they're all 58mm?

Interesting stuff though. What was the FerrariChat thread? Found this one and they list a few options (I think you need to login to see the pictures):

https://www.ferrarichat.com/forum/threads/348-thermostat.490525/

I've used the 56mm Facet part with no (apparent) problems - it's 82C (=180F) - IIRC it's also xref to the Vernet one mentioned in the Ferrari 348 thread:

https://www.eurosport-uk.net/shop/index.php?main_page=product_info&cPath=1_5&products_id=22

The 28mm diameter bypass plate on the MotoRad would seem on the limit for a guaranteed seal, so a few more mm's that the others offer would seem safer perhaps.

There was another linked FerrariChat thread where someone was trying alternative 'stats and the conclusion by someone else was "why didn't you just buy the correct part to start with as it's always been available?" - is there echoes of that here ?

 

[Dr.Jeff]

Guessing this is a typo, as pretty sure they're all 58mm?

My original Savara is 56mm and all of the aftermarket units that I'm familiar with are 54mm. But there may be others?

 

[Ics19]

My original Savara is 56mm and all of the aftermarket units that I'm familiar with are 54mm. But there may be others?

I was looking at the 't-stat housing measurements' not the actual t'stat, but I'd mis-read it anyway - I can now see it's the "opening" that fastfiat81 was quoting, not the diameter of the recess that accommodates the seal: Just checked an old housing and the top recess diameter is 58mm, but the opening is only 52mm, so even a 54mm t'stat won't fall through

 

[Dr.Jeff]

I was looking at the 't-stat housing measurements' not the actual t'stat, but I'd mis-read it anyway - I can now see it's the "opening" that fastfiat81 was quoting, not the diameter of the recess that accommodates the seal: Just checked an old housing and the top recess diameter is 58mm, but the opening is only 52mm, so even a 54mm t'stat won't fall through

Thanks for clarifying that, I misunderstood what you were saying earlier.

And since you have a T-stat housing handy for measurement, could you also compare yours to the dimensions given previously regarding the depth/distance for the bypass opening? This seems to be called various things by different T-stat makers, but I'm referring to how far the T-stat must move in order to fully block off the bypass. If you also have any old T-stats laying around, please see how far they move in this regard. And I'll see what I might have available to measure. I think this dimension is the most critical difference between all of the T-stats discussed.

 

[JimD]

I created a new "Thermostat Info ("box thermostat")" category under the "Heating and Cooling related threads ("box hvac")" topic, and I put this post in it.

 

[Ics19]

could you also compare yours to the dimensions given previously regarding the depth/distance for the bypass opening?

Yepp, checks out ok at 37.6mm (so ~38mm as stated). The distance from top of body to top of bypass opening is ~42.2mm and the depth of recess is 4.6mm. So using fastfiat81's calculation with the 'stat sitting half way in the recess, means it needs to open to 40mm or more.

However, I think the following isn't correct:

Subtracting the 2mm for the rubber gasket (half it's thickness) to each thermostat yields the following...

This seems erroneous as the thermostat is already sitting halfway in the recess - the original spec of the 'stat should just apply, i.e the Stant Superstat 45378, MotoRad Napa 138 and Wahler will all block fine once fully open. There is no need to apply the 2mm subtraction, so could possibly explain why no ones had a problem using the 'stats sold be the usual vendors?

 

[Dr.Jeff]

However, I think the following isn't correct:
This seems erroneous as the thermostat is already sitting halfway in the recess - the original spec of the 'stat should just apply, i.e the Stant Superstat 45378, MotoRad Napa 138 and Wahler will all block fine once fully open. There is no need to apply the 2mm subtraction, so could possibly explain why no ones had a problem using the 'stats sold be the usual vendors?

To be completely honest that part sounded a little confusing to me when I read it. But I figured until I could get the parts in hand and visualize everything I wasn't sure exactly how to interpret it. But if the additional 2mm is not subtracted, doesn't that mean the T-stat needs to open further? If the distance needed is 40mm then none of the T-stats (including the original one) open that much. Maybe @fastfiat81 can clarify it for us, I still might not be understanding 100%.

@Ics19 thanks for the feedback. I'm not sure when I will get my hands on my stash of spare T-stat related stuff - it's pretty well buried.

 

[fastfiat81]

On my housing the distance from the bottom of the recess to the top of the bypass opening is 38mm. The rubber gasket is 5mm thick. The distance from the top of the recess to the bottom recess where the gasket sits is 4mm. The groove in the gasket is half the thickness so about 2mm. So that makes the distance a t-stat has to expand is 40mm.

Great discussion and you guys are correct. All thermostats will expand enough to close the bypass opening.

 

[lookforjoe]

I'm curious what the one the op bought looks like - searching for Motorad 4108 doesn't come back with any products - 14108 gives this as one option

Stant 14108

the listing for Toyota Prius OEM looks like this - more like the Savara in construction, if I recall correctly - but smaller opening I think

EDIT - original t/stat on top in my pic here

 

[Dr.Jeff]

All thermostats will expand enough to close the bypass opening.

I'm afraid I confused this question in my last post (#10). When I looked back at the specs for the T-stats you posted in the original post, I accidently viewed the "distance between flanges" instead of the "opens up" distance. So I was mistaken about none of them going to 40mm. Sorry for that.

 

[Dr.Jeff]

searching for Motorad 4108 doesn't come back with any products

You are correct, as I stated in one of my earlier posts. If you go to the MotoRad site and cross reference the Stant number (14180), you get MotoRad # 298180. That's how I found the other MotoRad options (298170, 298190, 5298180, and 798180). The dimensions for those numbers match the Stant 14180 almost exactly. I think somewhere the MotoRad number was just misposted as 4180.

 

[Dr.Jeff]

One thing I'd like to compare is the MotoRad "high flow" version for the VW applications to the "standard" one we are discussing here (298180), in terms of the opening/flow size. I have a VW high flow MotoRad (#2034180), but not sure how we can compare them (I don't have a 298180)? Suggestions on exactly where to measure so we can compare?