Hello jag lovers,

I recently inherited a 1988 xjs v12. I have had various issues which I’ve been working through. It’s been running perfectly recently but has started to overheat very quickly. I notice the aux fan is not coming on of its own accord and I can only get it running by turning the aircon on. The fan also does not continue to run after the ignition is turned off like it usually does if warm.

additionally, the engine is idling at about 1500 in park and neutral - it comes down in drive to 900 but this is also a new issue. Was fine one day, the next it was all heat!

please may I have some assistance?!

thanks!

 

as an aside, I am aware that in the long run I will need to replace and work on the whole cooling system. But would love some help as to what specifically Might be going wrong here given it has had such a sudden onset.

 

The cooling system if proper is fine. No need to re-engineer it, just get it working properly.
Start with airflow. Is there any trash /leaves between the A/C and the radiator? ( very common). Then check the seals between the radiator and chassis. You need air to go through the radiator core not around the edges.
Is it properly filled with coolant?
Jaguar has 2 radiator caps. Check the owners manual to see how to fill it. It’s not what you think.
Next how old is the coolant? No more than 2 years old I hope. If older than that you are risking really serious engine problems. The coolant is in Aluminum block, heads, and passages . In that block are steel studs holding the head on ( 29 on each side ) then the radiator is brass and there is steel core plugs and covering plates not to mention cast Iron impellers on the water pump.
All those dissimilar metals cause electrolysis that quickly builds up and ruins things if not replaced on schedule.
Not to mention that tap water is far from pure and will leave deposits that plug up the radiator core.
So always use 50% antifreeze and 50% distilled water. Replace at 2 year intervals even if not driven!
Then there is the rubber issue. Because of a lack of airflow through the engine compartment rubber hoses take a real beating. Cautious people replace them every 5 years. I personally think that good rubber will last 10 years as long as there isn’t a lot of stop and go city traffic in those 10 years. If there is, I’d spend the time looking for good silicone hoses. And be done with routine replacement. Nope, there is no Kit! You’ll have to search for each hose individually. Maybe connect a few bends etc.

Finally, dealing with fans. The original fan has a finite life. In addition to the clutch wearing out It has been known to fly apart causing serious radiator damage. New replacements are much better.
One last issue. The distributor. In your owners manual it tells you to add oil to the center of the distributor. I’ve never seen that done. Until overheating causes a problem.
What happens is the advance mechanism freezes up and the timing is off. People don’t notice it because the car still starts and runs smoothly. ( thank you V12. which is a really smooth running engine)
But if the timing is off, the car will run hot!! And probably idle wrong as well.
Ask, I’ll tell you how to check and how to easily solve the problem. It will only cost you a few drops of oil.