1984 Jaguar XJS from North America - Comments

Well, I have a heating problem. it likes to get Really warm really quick, but that's expected with a V12, and the interior is in ruff shape, but I haven't put that much money into it I've only had to replace the starter.

I have a sports tuned transmission and this car can move if I put it down, I highly recommend getting the transmission tuned up, it makes that V12 act like its suppose to, havn't lost a race yet.

Very short review, but I am interested in the transmission tune up for better performance, have not heard of that before.

If you have an overheating problem, you must fix it immediately or your engine will die (actually, you'll drop a valve seat and your mechanic will not want to deal with the extra labor involved in getting the head off these). These engines do not run hot (ever) unless the cooling system is in need of maintenance. The "hot running V-12" myth is just that. They run at 94C. That's hotter than a Chevy V-8, but not all that hot. The thermostats keep them at correct temperature provided the rest of the cooling system is in decent shape. Some morons actually put cooler thermostats in, thinking that this will "fix" an overheating problem. It won't. The correct temperature is 94C. This is the designed temperature for maximum power and efficiency. If you put in cooler thermostats, the car will run cooler (with less power) longer, but once warm, or on a warm day, the car will overheat. This will happen until you fix the cooling system.

Usually, the radiator is blocked and usually, the owner can't face this simple fact. Even a partially blocked radiator will send the temperature through the roof. I cannot emphasize this enough. Aftermarket fan assemblies will not fix a blocked radiator and the original equipment is more than adequate for racing applications.

Also, this engine cannot tolerate being run hot. Aluminum engines must never be allowed to overheat-not even once.

You cannot neglect the cooling system in this car. I have owned enough of these to know that the temperature gauge rests 1/2 to 2/3 of the way between C and N in a properly operating engine. Any higher is too hot. BTW, you can run these at 120 mph ALL DAY LONG and never get outside this range. If you can't, your cooling system needs work. There is nothing wrong with the DESIGN of the cooling system or any of it's components. This is another common myth.

Most used V-12 XJs need a new radiator because of bad factory maintenance that stipulated adding Barr's Leaks to the cooling system. They're all clogged with this garbage from the first owner (who took her to the dealer for maintenance). Do a complete cooling system flush. Twice. Then change out the radiator and install original thermostats and gaskets. Remember that this is a very unique engine. It has probably the highest compression of any factory engine made, it advanced the art of fuel injection and requires careful attention be paid to its operating parameters.