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Discussion Starter #1
As I am working on the cooling system on my Shadow-1, I had ordered a lower temperature thermostat from Flying Spares in the UK.

My reasoning is that with the Porsche cars I usually work on, especially the 80's and 90's water-cooled models have thermostats which were specified to run at temperatures compatible with helping emissions to export the cars to the USA, normally around 90 degrees C. Typically in Europe we change these thermostats to cooler running ones, in the region of 75 to 78 degrees C, as the general consensus is that it is kinder to the engine, as it will not be heat cycling through as wide a range of temperature (but these are aluminium engine casings and bores usually on these cars.

Flying Spares describe this as a beneficial upgrade, what is the consensus here?

I have also read with interest the many threads in here with people using the Stant or Napa thermostat, as the go-to option. But I can't find much talk of why people are choosing it, only reference to an article in what sounds like a club magazine or something.

Is the Stant/Napa item a lower temperature thermostat, or is it just a better design or more easily available option?

I have also heard of people drilling a hole in it, presumably for making it easier to vent or bleed the system? Does the original not have a bleed hole, or is it just the Stant item does not have one?

Also mention of a jiggle pin being transferred, so I suspect it is just the Stant not having a jiggle pin or bleed hole, but I am interested in clarifying this.

Half the reason I am mentioning this is that Flying Spares will not have the low-temperature thermostats in stock until August, but have offered the alternative of the standard genuine part. So weighing up my options of waiting for the low-temperature version, getting the genuine standard part, or ordering the Stant/Napa part (Recently one of my parts suppliers in the UK is selling Napa parts which used to need importing)

All the best
Jon
 

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The reason why people buy the Stant; simple ..it's cheap. The original does a fine job and contains plugs which will melt away in case of failure to promote flow.
I prefer the original thermostat.
 

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A cooler running engine, has a tendency to sludge up more, especially if you live in the city and like to let your car warm up in the drive way.
The quicker an engine warms up and gets to operating temperature, the better, and this is not achieved running a cooler thermostat.
When burning fossil fuels, water vapour is produced, a cool running engine takes longer to burn off the water vapour.
With out the water vapour properly being burned off, it collects in the rocker cover and in the valve train area, causing it to mix with the oil.
This mess in turn eventually ends up in the sump making things even worse.

An engine that runs at the 80 and even better at the 90 degree mark runs cleaner, gets better fuel economy and wears less _ more then 80% of engine wear occurs on cold start up.

If an engine is over heating because one is running a hotter thermostat, it's because there is something wrong with the system.

Here is my engine in my Mark VI Bentley 20 years later running a hot thermostat after it was rebuilt.
Zero sludge and varnish build up in the valve train area, none in the sump either.
The car has never been allowed to idle in the drive way from cold to warm up.
It's started and the oil pressure is allowed to come up, and is driven gently until fully warmed up.

The core in the rad was replaced when the engine was done and the block has zero silt in it.


28412
 

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For the amount of money saved buying a Stant thermostat, which does not fit properly without getting an rubber "o" ring, cutting it to get it to fit, drilling a hole in it as a vent when filling, It is not worth it.
The correct one with the plugs that melt, if the engine overheats, is the right one to get.

Jake.
 

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After a drive, I open the oil filler cap to let the engine out gas and have no issues with the brown mayo.
 

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Discussion Starter #6
Thanks for the comments, all very interesting.

In particular the comment about moisture not being burned off from the engine oil promoted some thought.

My only experience with low temperature thermostats is with Porsche water cooled engines and it made me wonder why we do not see any sludge or emulsified oil in these engines.

Having thought about it, the engines I am more familiar with have an oil cooler and an oil thermostat, with typical oil temperatures within the engine being around 95 to 110 degrees C, which is probably what drives off the water content in the engine oil even with a coolant thermostat rated at around 75 to 78 degrees actually maintaining an engine coolant temperature of around 80 degrees C, whereas I am unsure of typical Shadow oil temperatures, or their oil cooling strategy.

With the Porsche engines we have found that running a cooler thermostat in the 75 to 78 degree C range, results in increased performance and fuel economy though, which is mainly due to cooler running cylinder heads resulting in a cooler intake charge temperature, resulting in an increased density per cubic inch of charge, but that is with aluminium heads and aluminium intakes (typically) which may be a completely different beast to the RR materials.

I think from everyone's comments I will go with the standard thermostat.

Many thanks
Jon
 

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Make sure you wash the flame trap. It is discussed in the workshop manual.
 

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I recently fitted the cooler thermostat you're referring to in my Silver Shadow 11 and I find that the temperature gauge needle now only barely reaches the lowest part of the white (normal) section on the gauge. I think I'll revert to using the original thermostat. According to everything I've read the cooling system on these V8 engines is more than adequate if everything is working properly. What seems to be most important is that the coolant should be flushed and changed at 2 year intervals using the correct coolant and not using corrosive flushing agents, water is adequate for flushing. The cylinders have wet liners and if any corrosion or crud builds up between the liners and the cylinder walls there is a risk of hot spots leading to liner distortion.
 

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In my professional opinion the Stant thermostat is a much better choice than the factory one. I'd say that easily half of the cars from new clients that come into my shop that we do a service on have most or all of the plugs melted or corroded out and many of them are seized closed. That is, they are not working at all. With no pellets left in the factory thermostat the engine takes much longer to warm up, a complaint we sometimes get is poor heat from the ACU in the winter and the failed factory thermostat is often the cause for this.
The factory service schedule calls for replacement of their thermostat every TWO years, this is rarely done now because of the cost of the factory one. Local RROC club members wrote up an excellent treatise on the factory vs. Stant thermostat, and from personal experience I stand 100% behind their statements. Drilling for a jiggle pin is not absolutely necessary, and an O ring is not needed as the housing gasket holds the thermostat in place. Read the article here and judge for yourself: http://rrtechnical.info/TeeOne/to95.pdf
 

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Shadow II, make the mix yourself with a quality antifreeze, ( HOAT my advice, no long liefe), and demineralised water.
That is ok for 3 years if you use a premium one.
 

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Yep Jean, I only use the old fashioned Bentley Green antifreeze & summer coolant mixed 50/50 with distilled water. I get the concentrate from Introcar Ltd or Flying Spares, it's fairly expensive but probably worth it for peace of mind. I always flush the heater and radiator separately and remove both engine block plugs and flush the engine with a garden hose. I recently replaced the filler cap, steam valve and level probe seals in the header tank as they had perished. During the 11 years I've owned SRH37125 I've never experienced deterioration of the lead pellets in the thermostat but I usually change the thermostat and gasket with each coolant change, overkill maybe but the old girl is worth it.
 

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Hi Larry,
Bentley coolant is ok for 3 years.
You could change thermostat every 6 years, each 2 cooling replacement.
And keep the old one in case.

You are in any case taking great care of your car, that is the secret to keep them and enjoy them.
Regular and quality maintenance, regular use, at least once a month 12 months a year.
 

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Thank you Jim. The problems with the OEM thermostat are well documented, particularly galling and sticking in whatever position they happen to get stuck in.

I am the third author on, Thermostat Issues and Selection, and I stand behind that research even more strongly now than I did when it was originally conducted.

It was also picked up by the author of Tee-One Topics in Tee-One Topics, Issue 95.

The design of the OEM thermostat was horrible, to put it mildly, and I will never put another in any of my cars and would advise others similarly.

And I agree with those who state that running an engine cooler than designed causes more wear, not less, over time.

I also started using extended life coolant years ago, and converted to Peak Global Lifetime coolant in both my cars somewhere between 8 and 10 years ago, depending on the car. Not even a hint of trouble in all that time. I know plenty of others who've ditched "classic green" long ago as well. So long as you avoid DexCool formulations you should be perfectly fine with modern long-life or lifetime coolants that are not DexCool formulations. I've posted plenty about that here in the past, too.
 

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Discussion Starter #14
Well it seems that getting a Stant #13558 thermostat is a bit of a problem at the moment.

I could not find them anywhere in the UK, but did find them listed on the RockAuto parts website in the USA, who I have used before for some unusual parts, ordered it, and they have now come back saying they have none.

Tried to order the NAPA 136 version from NAPA, But NapaOnline do not seem to be able to ship them at the moment.

Originally I had tried to buy a low temp version of the original thermostat from Flying Spares, but they have no stock for a month or two (and now you guys have educated me, I want the Stant one really)

Any other sources for mail order on the Stand 13558 that anyone can recommend?

All the best
Jon
 

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Right now it does appear that the Stant 13558 thermostat is "made of unobtainium." Even Amazon's listing for the Stant 13558 indicates it's out of stock and they don't know if it will be available again. It is, however, still listed in Stant's own catalog, and interestingly is now noted as OEM compatible for the SZ series cars.

I have actually written to Stant through their Contact Us page to ask if the 13558 is temporarily or permanently out of production, and whether any other thermostat in their current catalog meets the dimensional and temperature requirements that our cars need. I'll be curious to see what I hear back.
 

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Discussion Starter #16
Right now it does appear that the Stant 13558 thermostat is "made of unobtainium." Even Amazon's listing for the Stant 13558 indicates it's out of stock and they don't know if it will be available again. It is, however, still listed in Stant's own catalog, and interestingly is now noted as OEM compatible for the SZ series cars.

I have actually written to Stant through their Contact Us page to ask if the 13558 is temporarily or permanently out of production, and whether any other thermostat in their current catalog meets the dimensional and temperature requirements that our cars need. I'll be curious to see what I hear back.
Thanks, I thought it was just me suddenly not being able to find it.

I also found a reference to gates one being the same or similar, but when I have tried to get the Gates one today from a local motor trade supplier we use in the workshop, they said that the number did not cross over to anything that Gates catalogue list, or anything by another manufacturer listed.

I have never had so much trouble getting a thermostat for a car, and having been a mechanic for 30 something years, that is saying something... Usually on most cars, including the ones I specialise in, I always buy genuine thermostats, whereas for other parts I am fine with OEM... However on this car I can see the original thermostat seems to have shortcomings, but at the moment it seems I can't even buy one of those... Which as I feel committed to getting the more modern design Stant one, seems like an expensive stopgap, even if I could get one of those either.

Then again, I have not driven the car in years, so I should be patient :eek:)
 

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Who knows why certain items become unavailable? Virtually any Stant thermostat you can name, including the 13558, that is listed in their catalog is generally dirt common and readily available. It certainly was when I and my coauthors were doing our research for Thermostat Issues and Selection.

And given the number of cars for which the 13558 is suitable (see: 2017 Stant Catalog and Stant Vintage Guide) it has clearly got to have cross-over equivalents from any one of a number of major aftermarket thermostat makers. We just stopped once we had determined two very commonly available thermostats back when we were researching.
 

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I came across the following website (PartsTech) that listed equivalent thermostats. I looked up one on amazon and came across the one shown in the pic below. If the stant does not become available soon we may have to research a new substitute, like the one shown.


Geoff
 

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Stant 13558 = BMW 11 53 1 251 041 / Behr TX 17 80D / CALORSTAT BY VERNET: 1528.80J

Or the cooler version: 4231.71D

You can easily source it in the UK / EU.

I prefer Vernet/Calorstat. As a bonus, it comes with the grooved "o-ring"

The grooved o-ring is: Volvo 1218375, Peugeot 245057, REINZ 70-25455-00
It is from the '70s/80's PRV V-6 thermostat gasket.

I don't bother to drill a small hole in my thermostat since I have a cooling system vacuum tool that extracts most of the air from the cooling system and said vacuum is then used to fill the system.

Minimal to no cooling system air bleeding is needed when air is evacuated.

Coolant - I use GLYSANTIN® G05® Concentrate in all of my cars. In a pinch I use G03.
In the US it is branded as Zerex G05. I think the Peak global lifetime is the same product?

Motorad is JUNK

Stant 13558 is the recommended replacement for these US market cars:
BMW 2500 1971
BMW 2800 1971-1974
BMW 2800CS 1971
BMW 3.0CS 1972-1974
BMW 3.0CSI 1972-1974
BMW 3.0S 1971-1974
BMW 3.0SI 1975-1976
BMW 528I 1979-1981
BMW 530I 1975-1978
BMW 533I 1983-1984
BMW 630CSI 1977-1978
BMW 633CSI 1978-1984
BMW 635CSI 1985
BMW 733I 1978-1984
BMW BAVARIA 1972-1974
ROLLS-ROYCE SILVER SHADOW 1966-1976
ROLLS-ROYCE SILVER SHADOW II 1977-1980
ROLLS-ROYCE SILVER SPIRIT 1981-1995
ROLLS-ROYCE SILVER SPUR 1981-1998
 

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I put up the Motorad just as an example that there were equivalent thermostats available - I chose it from the list at random. Thanks for the recommendations.

Have you ever used any of these thermostats in your Silver Shadow. I'm interested in how they perform.

Geoff
 
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