HI Greg, i wish it was only 85F here in central TEXAS, just checked right now its 102F where i’m at!
it is well known by the old timers , Jaguar cars just cant kool in this kind of weather!
the old mechanics have tried years ago, and best option is leave the car home and drive something else!
i know this is off topic, guy i know in Saudi ( car guy )said nobody buys older Jaguars! all over heat!
120F is common! Yikes.
ron
Old British cars were built for UK. Luckily NW United States is very similar weather.
My old Volvos are super toasty in the winter, heaters blow so warm! I’m sure they’re tested in Sweden.
DHS , i see you have your stats in front of you!
question; what is the outside diameter of them ,what year V12 do you have?
seems when buying there are 2 different size O.D. 2 inch, and 2 1/8 inch O.D.
thanks from ron
I have four different brands and all are 2 1/8, this is in a 94 model. I tested all of them and only the Gates went past 42mm, since I was hoping for better flow I made the bypass extension so I could use the MotoRad’s.
I don’t usually post on this forum, but I have some information that may be useful to you. My research on E-Type thermostats has been painstaking, and I’ve begun to document it in an E-book. I’m publishing one chapter a month, and it will be a few months until I get to the V12’s, but I’m announcing each chapter on the E-Type list if you’re interested.
My research into S2 and S3 E-type thermostats indicates that the depth of the bypass probably started out at 1.6" as cast, and was machined down a few thou to give a good sealing surface. For the S2 and S3 E-Type housings, that depth is between 1.607-1.625", within a hair of 41mm. I doubt the XJS was any different. That’s the depth below the bottom of the thermostat flange. A proper thermostat will just seal the bypass a full open, which will come about 10C above start-of-open. At that point, the bypass spring, should compress no more than a millimeter or two.
I’ve also accumulated a large collection of thermostats, and I’m just waiting on samples of Dayco and Calorstat (Vernet) to wrap up my research. So far, few brands actually fit and work correctly. Stant and Gates have or recently have had the same corporate ownership, so it should come as no surprise that their products are identical, and they work. Of course, if you can find an original Western Thomson Waxstat, those are unique and actually fit.
But of the others I’ve examined, including Tridon, Motorad, Quinton Hazel, Beck Arnley, Unipart: all of them appear to come from one factory (in fact, my Tridon samples are actually stamped “Motorad”). Even some original label Jaguar stats are of this pattern. And all of them are too short, some by as much as 3mm. I wouldn’t be modifying my housing to accommodate an inappropriate thermostat. Despite the claims of higher flow, or the more dubious claim of ‘fail-safe’, none of these thermostats have a mod-worthy advantage. In my E-Type, I use a Gates and that’s what I’d recommend (or the equivalent Stant). You can use a Gates/Stant Superstat if you have a problem with stability when running cool, but I doubt anyone with a Jaguar has that problem. Since there’s a widely available product that actually works, I don’t see why you’d fool around with it.
Looks like a gimmick device to make people think they can make an inefficient cooling system work better or a failing clogged system work period. I wouldn’t waste my money.
Thanks for the info Michael. I’ve gone ahead and ordered Gates 180F thermostats, even though I just replaced mine with Motorads.
I noticed the Gates thermostats actually have info about the bottom bypass! Do those measurements match your work?
Note that the thermostat housings on the E-Type SIII are not the same as the thermostat housings on the XJ-S, yet they both apparently fit the same thermostats and share that 41mm dimension to the bypass port. Evidently Jaguar was serious about that dimension. Makes one wonder why so many companies offer incorrect thermostats.
The Series 2 and Series 3 E-Types don’t have the same housing, they don’t even have the same number of cylinders, but their thermostats are interchangeable. It’s because automakers don’t design thermostats. My guess is that the Western Thompson guy came by with his sample case, said have a look at this, and the rest is history. You’ll find other cars of the period used the same item. Fiat comes to mind.
There really seem to be only two factories turning these out for the aftermarket world wide. (I’m not sure what’s left of Dayco or Wahler, and Calorstat only has a Volvo thermostat which may fit by accident) So if one isn’t doing it right, that’s going to impact a big chunk of the market. How did it happen? Not sure, but Porsche uses almost the same thermostat, except 3mm shorter and with a larger bypass valve. That’s the only clue I can offer.
The bottom bypass on the Gates/Stant thermostats in my collection are all about 27mm. The Superstats don’t seem to have an air bleed. The regular thermostats have one, but it’s a tiny hole in the poppet, hard to see. For XJS applications, you can simply drill a single 1/16" hole in the flange to effectively bleed air. The air bleed/jiggle valve only matters on initial fill, so smaller is better, but it may take some time to “burp” the system.
Wow. That pretty well explains it all. And it adds justification to the idea of stepping up that bypass port by 3mm.
I have seen thermostats that didn’t have a bleed hole per se, but the moving plug portion of the thermostat had a notch in the edge that would provide a leak even when fully shut.
I personally think a genuine jiggle pin or ball is a good idea here because I can imagine an air bubble getting up against a tiny hole and effectively plugging it.
I wouldn’t build up the port to match a poor fitting thermostat. Not when a reliable, well fitting alternative is readily available.
The regular Gates/Stant have a tiny notch. If the Superstats have one, it would be hard to see because of the weir-valve design. A 1/16" hole is fine. This is only going to affect initial fill, and the very worst that happens is that you would have to walk away for an hour while the air slowly bleeds out.
I found some Gates XJS stats which are said to be 33mm, instead of 43 , so would be 10mm off ?
Well 33mm would be to short for the XJS V-12, the E-Type V-12 does have a different set up for the stat housing but still has a bypass, I never measured the E but the double action stat fixed my over heating. Because of the air filters the stat housing are different on the XJS, it could be possible the E only needed 33mm and the stats are for that engine.
OK, just looked at your site the 33mm is cold so a Gates will open the 10mm you need to block the bypass, I would buy one and test it in boiling water.
Dan
thanks for clarifying the “cold” measurement.
I’ve already changed the stats, , using those from SNG, but didn’t measured them before fitting.
may be worth checking the proper extension , but this need to take them out again…
or is there a way to check them in place, like by checking the temp of the water in the bypass ?
Well SNG might be able to tell you the brand they sell, but the right side is not to bad to check, if it’s a Gates your done. If not just leave it off and order the Gates then go pull the left side and in a few days you will get the Gates to install. Checking the bypass will be hard.
I found the information on some pictures I took while checking the stats before fitting them : the brand is “waxstat”, PN C37925*
they seem to have enough “reach” when hot
