My XJS V12.....like..most ...runs hot far too often.....any tips on how to fix or at least improve this issue??

 

The biggest one is having the correct thermostats. As Grant explains in this post: https://www.jaguarforums.com/forum/x...2/#post1302110 most thermostats don`t have a long enough `foot`to block off the bypass, so a large percentage of the coolant never goes through the radiator. If you can`t find the Dayco, a Gates 33188S will work, but you need to drill a small bleed hole in the flange.

The other big thing on V12`s is the space between the radiator and condenser seems to be a magnet for debris - leaves, aspen fluff, cat fur, you name it. I have pulled all sorts of stuff out of the radiator that was blocking the airflow. Unfortunately, radiator out is the only proper way to do that and clean the radiator.

 

Have you....... tested the fan clutch? Added water wetter or had the rad flushed with a good product? Verify resistance readings on the sensor?, tested aux fan? consider adding manual toggle for aux fan? ignore the temp gauge? Tried a handheld IR temp gauge?

 

How hot, and under what conditions?

Cheers
DD

 

These are the items to replace/service to get the car running correctly (mostly already mentioned above) but you would be best to do the lot and have done with it:

• Remove rad and clean rad fins and blow out the condenser and oil cooler fins with compressed air
• renew all coolant hoses
• renew thermostats
• renew pressure caps
• remove LHS front wheelarch rear stone baffle and check overflow bottle is intact and the pipe to the wing tank is clear and properly attached
• check mechanical fan clutch and renew if deteriorated
• fill with good quality antifreeze
• renew all drive belts most notably the waterpump one.
• Bleed the system carefully (you can search on here for how to do that)

All the usual specialist suppliers can provide the stuff: eg SNG Barratt, David Manners, Coventry West.

Which model do you have, by the way?

 

Good list and I certainly agree with the "do it all" approach to V12 cooling systems.

But, as long as the radiator is out, and since removing it isn't a 15-minute thing, I'd assume it's internally clogged and send it to a radiator shop for a professional boil-out and pressure testing. Might as well go all the way !

Cheers
DD

 

I'm in Australia and had this problem. I fixed it by fitting twin ford falcon thermatic fans. I also fitted a new aluminium radiator and converted it to a cross flow setup. I also use Tefba filters in each radiator intake. On a 40 degree celsius day it runs cool, idling without moving.