After a long time of researching a lower temperature thermostat to replace stock 3 piece 190 degree AJ811788 thermostat with a perfect fitting 180 degree unit, now I got a perfect matching insert. If you got a 4.2 or 5.0 Denso car, I can offer a performance tune as well with an adition of lowering fan start temperatures by 10 degrees to match the new thermostat. Now this is not a requirement but if your pushing more power and or race the car the track , this would be a nice addition.
Price with shipping in the USA will be $70
If your interested in a tune we can discuss.


Should fit all models using the 3 peace AJ811788 thermostat

1. Jaguar XF XFR 4.2 V8 & 4.2 V8 R
2. Jaguar X150 XK & XKR 2006 on 3.5 & 4.2 V8 & 4.2 R
3. Jaguar S Type 4.2 V8 20063 to 2009 from vin N52048
4. Jaguar X350 XJR 4.2 V8 2006 to 2009 From vin G49701

 

There are a lot of variables to take into account when swapping out a thermostat.

Are you remapping all the temp sensors to differentiate when the car should enter open loop? If not, your introducing a lot of possible error signals to the ECU.

In old school days, you replaced the temp sensors to compensate for a lower thermostat as they were technically on/off switches.. Maybe today they are just variable, and can be addressed in programming?

Swapping thermostats is no simple win-win process.

Peace!
Vince

 

180 & 190 is just starting opening temps, full opening is around 10-12 higher than this.
On our cars 180 starting temperature thermostat car will run aprox 188-195 range (have it in my car) vs with 190 thermostat car runs 196-203 range , this might be higher with higher temperature climates. Fueling and going into open loop is not effected as the threshold is lower than 180 for this. No reprogramming is needed and no ECU codes, car will just run slightly cooler with longer time until fans kick on. With reprogramming of the fans will stay consistently cooler and is easier to keep it cooler vs 190 thermostat and having to fight it by lowering fan temperature. Probably no need to change for your everage driver not pushing the car much, oem 190 is perfectly fine, But in hotter climates and with pushing the car harder, slightly lower temp thermostat will give an extra cushion, car will stay cooler so timing advance won't get as large of a retard thus better performance.

 

Do you have the thermostat for the 5.0?

 

I believe it only fits the 4.2 models mentioned above