What degree thermostat are you guys running in your 2000 s-type 4.0. I'm at 5000 ft in Colorado and it gets purty cold.

I would stick with OE temp. If worried about the cold I would make sure you have fresh coolant mixed at least 50/50, but no more than 70/30. Honestly as long as the thermostat is operating properly and is not a cooler temperature rating than OE then I wouldn't be concerned about it, but it's always good to replace it on a regular basis or whenever coolant is changed.

I wouldn't go hotter as warped heads would not be funny.

And colder isn't likely to help.

So +1 for OE.

If it's not hot enough I wonder if there's a fault of some sort - blocked matrix or whatever.

+1 on original thermostat, which begins opening at 85 C.

Ok, the reason I asked is I check the flow out from the thermostat and was getting a reading of 180-185 after a 20 minute run. Seemed a little cool to me, I thought it should read over 200??? The real question is what is the OME thermostat rated at. Just want to make sure I'm not to cold for the engine as I am getting a P1183 code which calls into question the thermostat.

Thermostat begins to open at 85 C and is fully open at 100 C to 102 C.

What is the battery voltage across the terminals with the ignition off?

Can't say for sure, but 185 doesn't seem too cool for an external reading after a freeway run on a cold day. The coolant inside the pipe may well be around 200.

If you do want to try a new thermostat, I HIGHLY recommend testing the new and old ones side by side in a pot of water on the stove. Sordid details here of my experience with a failed original thermostat, followed by a bad replacement:

https://www.jaguarforums.com/forum/s...rature-186873/


I could have saved myself a lot of grief by testing the new thermostat before installation.

Via OBD, what is ECT (as well as re-reading what you already did)?

ECT is what the car sees and used to flag codes as well as command fan speed etc.

What you may have is a flow problem of some sort and if so the thermostat is not the issue.

BTW no harm changing the thermostat but I would not depart from OE.

People usually are surprised at how HOT these cars run! (It's done for emissions/fuel efficiency.)

Not all T-Stats function the same way. Not only is the temp rating important but also the rate at which it opens.

Take a good look at the spring and compare the new stats spring to the OEM. If the new stats spring is short as compared to the OEM you might have slow warmup times which can result in DTC codes.

I'm not saying to buy only OEM. But a guy / gal (yes there are only 2 genders) should take a careful look at all aspects of replacement parts.

Switch the odometer to read temperature, and see what you run at.
I have just replaced a thermostat and fitted an 80 degree in stead of the factory 84.
My temperatures are between 95 and 100 typically.
(press left stalk and hold while turning key, until TEST MODE appears, then press repeatedly until TEMP IN. Shows temp in degrees C.
IE 256 equals 25.6 degrees C)

I don't think his era car can do that.

But it can do OBD

I don't recall the pre-facelift X200 having a left stalk that can be pressed in.

For NBcat, reading 12.11 volts, I know I have a battery drain somewhere just one of the 3 or 4 things I am sorting out, any suggest are welcome.
For Wydopnehrill, Thanks for the education on the genders, who would have known.
For CRT, True, no such stalk on the 2000 model, any other short cuts.
Many thanks to all. Mile High at 5280 ft in Loveland Colo.

Battery voltage across the terminals should be 12.6 volts at a minimum with the ignition in the off position for ten or more minutes. Try charging the battery at 5 to 10 amps overnight and retest it. If voltage is still less than 12.6 volts, the battery is suspect. Many random DTCs and other electrical 'gremlins' chased on these forums are ultimately the result of a failing or weak battery.

For NBCAY, yes, charging the battery over night gave me a 12.83 reading this morning, will watch it closely for a few days to see what develops
Thanks you NBCAT, that was a good idea.

a new expansion tank cap has solved my heat problem, now at 195 degrees behind the thermostat housing, 185 degrees in front. Was not building any pressure in the system.

Thanks all...