over heating xjs

David, Generally, I have found that when the temp starts rising in traffic and is fine on the freeway, it means the water pump is starting to go. Usually if the passages in the radiator are getting plugged is a much slower process and you would have noticed the car running hotter on the gauge in ever increasing amounts.

Cheers Webserve

Check your fans. It's likely your mechanical fan clutch is bad and you're not pulling enough air to cool things down when you're not moving. Also, check to see if your electric aux fan is coming on when the engine is running hot.

Neither fan is necessary when you're at speed on the motorway because there's enough air being pushed through the radiator by the motion of the vehicle. They're critical in stop and go traffic, however.

Regards