Late last fall I saw that the thermostat that came with my Welsh Enterprise Alum. tower was not allowing the engine to get up to 185 F on cold days except when waiting at lights. I replaced it with a Gates 33948 and was operating at 195-201 F.
Both are 84 C and appeared to open the same on the stove top. Now as summer approaches I find the temp. 197-203, so at least one fan is running all the time. So today I swapped them again, and now running at 187- 192 F, except when waiting at lights. The engine temp. also drops back more quickly when I begin moving again.

So it looks like I have summer/ winter thermostats. Time to put a petcock that will connect to a hose on the radiator so I can remove fluid without making a mess.

 

I added a petcock to a copper radiator on another car and then an extension for a hose fitting for that purpose. The plastic radiator has screw threads so there should be a fitting of some kind that could be added and modified.

I continue to keep a suspect eye on my engine temp after last Fall's over heating problems and have a pump and thermostat on hand for the next level. Like you I hate to dump $25 of coolant with every system problem.

When motivated to change the pump/thermostat out I will figure out how to provide a drain as you describe.

 

I pumped almost a gallon out ot the system today, first from the pressure reservoir, then the tower, finally disconnecting the upper hose and pushing the pump hose down as far as the radiator. When I removed the thermostat I only lost about 12 oz., some of which was caught in a dish pan.

A lot of screwing around, but no where near the mess compared to removing the drain plug.

 

Does anyone know what the correct temp range should be?

 

JTIS states "the thermostat starts to open at 80 to 84 deg C (176 to 183 deg F) and is fully open at 96 deg C (205 deg F)"


(click on the image to enlarge it)

Note this applies to both Normally Aspirated and Supercharged models.

Graham

 

Are you trying to solve a problem or just seeking information? After a cross over pipe replacement with a new temp sensor my fans ran all the time which I considered a problem especially since that was in 20*F weather.

Another way to describe the 'Normal' engine temp is the specifications for cooling fan operation. In the AJ26/27 Jaguar Service Training Guide the low speed fan operation is turned on at 90*C(194*F) and off at 86*C(187*F), the high speed function is on at 97.5*C(207.5*F) and off at 93.5*C(200.5*F).

I would interpret that to mean that an expected operating range should be in the area of 86*C(187*F) to 97.5*C(207.5*F).

. . . but . . . that assumes that the temp sensor varistor measures 250 ohms at 90*C per Jaguar specifications. It took a 3rd new sensor before the closest measured 246 ohms at that point. That small resistance variation translates into about 5*C at 90*C as read at the OBDII Data Port. You really need an IR temp gauge to deal with the complete system.

Further discussion here: https://www.jaguarforums.com/forum/x...rature-138312/

. . . and a great buy on an IR temp gauge here: Nice Non Contact LCD IR Laser Infrared Digital Temperature Thermometer Gun HG | eBay