If the thermostat isn't controlling the water temperature when the vehicle is moving and the engine is under significant load, then there is something wrong and the system requires attention.

 

In heavy traffic, with 40°C outside temperatures, is an 82°C thermostat more desirable than an 87°C?

Unfortunately, we just discovered that KWE sent the wrong thermostats! They tested the valve lift opening and it was measured to be in standard, however, on inspection, the thermostat code refers to the 87°C, not 82°C!

Of course this was not intentional and KWE agreed to replace the thermostat, but the 82°C devices aren't available, and there is no expected date for them becoming available.

I've heard so many horror stories that I want ZERO risks, given the temperatures and traffic that I expect in Naples. I rebuilt both head gaskets and the whole cooling system (new shrouds, radiator, electric fans, expansion bottle, every hose, clamp, etc, etc) so I want, and deserve, complete peace of mind.

Should I wait for the 82°C to become available, or will there be little difference if I use the 87°C?

Tommaso​​​​​

 

Shouldn't make a lot of difference. In the end, proper thermostats do not change the ability of the system to shed heat. If it can't get rid of the heat with 87 it won't be able to to with 82.

 

82° say I !
I use these:
You have to drill a bleed hole 4mm diameter just inside the rim. Open at 180° Fahrenheit

https://www.rockauto.com/en/moreinfo.php?pk=366571

I have also recently bought 82° stats (not Stant) from Manners, work fine, and I would be amazed if they were not in stock. Tall to Jack Weston there.

 

In my experience the conditions you describe will tax the V12 cooling system a bit. Zero risk is the stuff of dreams but if you can tolerate the temp needle moving up a bit, you'll be fine. What is worrying is the temp needle climbing up-up-up with no sign of stopping !

Cheers
DD

 

Thanks, Doug, Greg and Jagboi, I appreciate the argument that most offer: what matters is the cooling system's efficiency, not thermos opening point (87C or 82C). Even Chris Knowles insisted that the 82C is superfluous and, was a US "cheat" to avoid litigious customers that wanted the temp indicator to be centered. Regardless, this time I will go with Greg's advice, as I am happy to err on the side of safety, if that error only costs me €20.

Furthermore, while KWE acknowledged the mistake in shipping the wrong item, Chris said that he would not get involved and simply offered me this link: https://www.sngbarratt.com/English/#...&saveBranch=FR - Greg, is this the appropriate 82C?

Ciao, Tommaso

 

It is, but JCP do not have them nor do SNGB.
https://parts.jaguarlandroverclassic...hermostat.html

This is what I used last time
https://jagspares.co.uk/thermostat-8...ebc3576-3.html

 

Thank you Greg. With these will I have to drill a bleed hole (4mm diameter) just inside the rim? Or can I install them just as they are?

 

Install as is, hole uppermost.

 

With the cooling system in good order, the higher temperature thermostat should be fine. The only loss in cooling margin might be if you have to crawl up hill in 40°C. The needle will start from a little further to the left, but soon rise to the same place irrespective of where it started. Especially if you still have the engine driven fan, it helps to push the transmission into first gear for very slow climbs. It keeps the revs up when you lift off the throttle.
It's a long time since I've driven in Naples, but coolant temperature wasn't my primary concern when I did. Traffic was quite complicated.

 

Thank you Pete and Greg, this Daimler Double Six will come to fruition this year, I promise! It's been in the works for three years now!

 

No!

The important number is the hot length from the "foot" to the large flange must be At least 42mm. Thermostats usually move 7-8mm from hot to cold, so you are looking at a cold length of at least 34-35mm.

The Waxstat brand thermostats I have bought from a Jaguar dealer were 32mm cold and only moved to 39mm when hot. The gap in the thermostat when fully open hot is about 5mm, so a 3mm gap to the bypass port when cold is really offering very little resistance to recirculation within the block. To control the engine temperature it is critical that the pathway to coolant recrculation within the block is completely closed. This is far more important than the temperature rating.

So make sure that the thermostat is extending to 42mm when hot ( I measured a V12 today and that is the flange to port distance) and you will have a properly working thermostat and bypass system.

I use the Gates 33188 thermostats and they work very well. I do have to drill a small (5/64" or 2mm) hole in the flange as an air bleed.

Craig

 

@Jagboi64 Good morning Craig!

I declare my ignorance & lack of experience but it makes sense that the most important thing for a cooling system must be heat exchange and, hence, the amount of coolant flow. If this were true, then, surely, flow redirection (proper valve travel) must be paramount.

I remember reading 2 papers (linked from this forum) four years ago - when I first joined this community - that attributed to incorrect thermostat valve travel the cause for many blown head gaskets (like mine). I remember reading that even OEMs were not operating correctly.

That's why I asked KWE (Chris Knowles) to actually open the box and measure the valve travel @ 82°C before shipping the two thermostats. I remember that very clearly, I visited his garage in person! That's why I'm rather disappointed that not only KWE sent the wrong thermostats in the first place, but also that now he left me to my own devices by refusing to take the wing ones back... this could have ended up with another blown head gasket. Again!

I think that the senior members here should publish a sticky post on this forum listing:
1. which thermostats are suitable for etch car.
2. where to find/buy them from.

Bottom line, Craig, is there an 82°C thermostat for a HE V12 that is ready to be installed out of the box (I fear that my mechanich may mess up the 2mm hole)?

I appreciate that the debate 82°C VS 87°C is far less important than correct valve travel, but, Craig, bear with me in my preference for an 82°C - look up traffic on the Amalfi coast & temperatures during summer (this car will be only a summer holidays car). I accept that I may be obsessing but, it's only a few euros, allow me to go with the "feel good" option 🙏
​​​​
Tommaso

 

Tommaso
Yes, the link to Manners that I gave above, repeated here:
https://jagspares.co.uk/thermostat-8...ebc3576-3.html

I think Craig is referring to the SNGB link to a waxstat, not to the link I gave to the Manners item. I have these in my car fitted recently, all 100% good.
Of course, the Gates stat Craig mentioned will be fine too, once drilled.

 

Thank you Greg

First of all, apologies to you: I read my post again and it reads as a critic to your comment. It wasn't.

I was trying to solicit a sticky, and then my disappointment with KWE led me to express the other comments.

Again thank you for the link, and apologies, I was not directing my comments to you.

Tommaso

 

No need for apologies, Tommaso. I was just clarifying.

 

I wish all Jaguar owners would learn a little about engine cooling.
Hot is good!! Especially the way most. XJS’s are used. It boils off the water and acids collected by short trips where the engine doesn’t get fully up to temperature.
Anything less than 210 degrees is fine!!! No your guage doesn’t read in degrees. That’s because royalty doesn’t want to be bothered.
You mere peasants 😜 worry about such things. As long as water is flowing and not boiling no damage is done! Water boils at 212 f with anti freeze it’s raised to over 235. f and the pressure cap and it’s still extracting heat at 250 degrees.

 

Either one is fine. Go with what you like! The engine doesn't really care.

The thing is, though, if the cooling system will only shed enough heat to cool down to (let's say) 98ºC it really doesn't matter if you have an 82º or 88º thermostat. Either one will be wide open at 98º and not actually controlling coolant temperature.

If you can get the cooling system working so well that it'll cool to below 82ºC then the thermostats will be controlling the coolant temperature as they constantly open-and-close slightly; hovering at 82º you might say. In Naples traffic with 40ºC ambient temps I have my doubt that this will happen..... but it might !

Cheers
DD

 

Does the Manners have a jiggle pin or hole? I couldn't see one in the photo. I've not used their thermostats, so I don't know what they are like.

Yes, I we looking at the Waxstat that SNG sells, and if it's the same as what the dealers sell it's not right.
The Gates are easy and cheap for me to get, so that's what I use.

 

Yes, the Manners item has the jiggle pin.