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Although I've previously recommended the Jaguar/Waxstat thermostats I thought try these Stant thermostats, number 45398, on a "I'll give 'em a whirl" basis. Others here have recommended them.
First I'll mention that the two I bought came with steam holes and jiggle pins. Others have reported that they had to drill the steam relief holes. Apparently Stant changed the manufacturing spec.
I did the pot o'water on the stove test. The closed dimension is 35-36 mm and the open dimension is 42-43 mm. Depends where exactly you take the measurement. Anyhow, I am satisfied that these will work fine in terms of blocking-off the bypass ports.
They begin to open just shy of 180ºF and are fully open just past 190ºF
That's very useful to know, when I looked previously the thermostats with the jiggle pins didn't extend far enough. These thermostats will work equally well in the 4.2 XK engine too.
Although when I looked it up on Rockauto it says it doesn't have a jiggle pin.
Greetings. I just had my mechanic do a pretty pretty full overhaul of the cooling system on my newly acquired XJS. New hoses, radiator flush, new water pump, new heater valve, new water rails (SS) and bushes, and thermostats. I had no idea when any of this had been done by the previous owner so I decided to have him do it all in one go. I got 82 degree Waxstats from SNG. They open in the pot of water to 42; which I think is the proper length.
The previous owner had drilled not one, but two larger than necessary holes in the thermostats (see photo). I noticed that the temperature fluctuated a lot before I changed everything.
After getting my car back, I noticed the temperature gauge creep slightly to the right of middle after a long wait in traffic, 32 degrees C with high humidity. It cooled down once I started driving. (see photo)
After this reading, I opened the new aluminium header tank and couldn't see any water. This got me concerned. So, I decided to go through the detailed bleeding procedures that Grant wrote about and Greg has commented on. There was a lot of trapped air that came bubbling out of the radiator. A surprising amount. Grant suggested that changing the water pump can really increase the amount of air in the system. I bleed the car twice, with a second time getting the front left quarter elevated a good six inches higher than the right. That made a big difference too. More air bubbles came out as water went into the cross over pipe inlet.
Since then, it takes much longer to get to the middle of the temperature gauge. It has only once, after sitting in a long traffic jam, ever gone over the middle (see attached). So, I am happy with the 82 Waxstats. When I have the stats replaced in five years, I will try the Gates 33188S for comparison.
So, what is the take home? Getting the system properly bled makes a huge difference. My 82 degree Waxstats seem to work well.
If the 6.0L XJS has the same radiator and cooling system as the XJ40 / Daimler Double Six, 88 degree stats will be fine. My Daimler which has 88 degree stats runs so much cooler than the XJS.
This was supposed to be in answer to Some Day Some Day as a follow-up to his post under "high efficiency cooling system upgrade." I started reading your post, Doug, and got off on the thermostat tangent! Looking forward to reading about your new stats.
Doug - good to know. I can add them to the list of potentials along with the Gates.
Charles: sorry, I didn't notice your reply here. Very interesting, however. I rather like your wood, too, from what little I can see of it. Curious about the oil pressure, however. Mine almost always sits basically dead centre. Your temp gauge in the top pic is about the maximum mine ever reaches in summer (at this time of year, Hong Kong and Japan seem pretty similar, temperature (and humidity)-wise.
that stants, also motorad are not made in the US anymore. they are made in israel now and come with the jiggle pins. I jsut went through this 3 times trying to get a stant one , only ended up with one. If you read the pub regarding stats you will see it comes down to the opening size. which you need it to open 43mm so when measuring the closed state of it you -8mm. I measured the one stant 45398 with the gates one and the gates was 35mm and the stant was 34mm. So im going with the gates as when I ordered 2 stants i got one stant and one gates. another gates is on the way.
V12 Thermostat Stant 45398
