I just had to put a quart of anti-freeze into my 95 v12! Should I panic? It has not been driven a lot recently has never overheated and it has been really cold.

Strangely the check engine light did not come on until after I put the anti-freeze in.

Fingers crossed.

 

Short answer no, don't panic. What you really want to find out is where has it gone. The cooling system is in effect a sealed loop (although some will over spill the expansion tank and into the wheel arch escape pipe on occasion which is worth checking out - air in = bad news). It may have also blown out of one of the rad caps or just be leaking from a hose (bottom are often oil damaged).

Find out the underlying cause for the loss and all will be well. And make sure you burp it properly after filling, it is notoriously difficult to get all of the air out of the system unless you follow the filling instructions to the letter (you might want to consider also fitting a venting "T" on a heater hose and installing some filters on the top rad hoses).

Cooling is THE most important aspect for the long-term health of your v12, it will happily do 250k miles if you look after it - let it overheat and you will almost certainly drop a valve seat (sooner or later) then its a head off rebuild. Also the light coming on intermittently suggests an air bubble in the system, something that requires immediate resolution or you may suffer hot spot damage.


P.S Overheating is anywhere north of the middle of the N, although on a 95 I think you temp gauge is different.

 

A quart? No, your car is almost 20 years old. If you aren't finding any puddles do a more thorough inspection.

I HIGHLY HIGHLY doubt your car is drinking coolant. Head gaskets are not a common issue on the V12.

How often do you check it? Has it lost that since it has sat or could it have been gone before parking it??
There are a few things that could happen here. The coolant is leaking out of a specific area and the coolant is not sitting lower than that area.
It could be leaking (or have leaked before parking) onto the exhaust or running down and spreading out so there is not an appreciable puddle.

My car is seeping out of the top hat seals on the coolant rail. It isn't very detectable because it immediately hits the exhaust manifold.

If you don't want to try to hard to find the leak then throw some UV dye and then hunt around with a blacklight.

I'd check the weep hole on the water pump as well.

The engine light may be totally unrelated to this issue and something else associated with parking it caused it to come on.

PS: never assume overheating is middle or north of the N. These cars are 20-38 years old. If you own an XJS please buy an IR thermometer to check temps and verify your actual temperatures.

My car can run over the N which to some people is OH HOLY !@# TURN THE CAR OFF IT HAS DROPPED A VALVE AND BLOWN A HEAD GASKET THE XJS IS DONE FOR. but this is actually about 180 degrees on my car.


Also I have pegged the H after blowing a heater hose and my engine is fine. These are very well built engines. They aren't extremely prone to total failure as a result of overheating, they are just prone to overheating because the stock cooling system is JUST ENOUGH. so if it is old and anything isn't correct it will probably overheat.