1989 v12 running hotter

[al.sharp1]

Since I got the xjs 3 years ago the temp gauge sat 'mid N'. Top hose leaked last year and I replaced it and bled system. Since then on start up the water light comes on for a minute or so and goes out and stays out. Is that drawing coolant from expansion tank? Today on a dull 6° run for Drive it day my gauge rose slightly above the N while sitting at roadworks and stayed there. Is this normal? I'm now using Shell V power fuel and someone (non qualified) suggested V power makes the engine run hotter. Is that true?

[davidr]

Hi - any sign of running hot is a red flag with a V12. The golden rule is Don't Cook It! The V12 is a very robust engine but one thing it won't stand is overheating and warped heads, dropped valve seats etc all become a possibility if you do.
The temperature gauge should sit at the low end of the N - if its been mid N for a while that indicates its running hotter than it should. Getting above N on a relatively cool day suggests the cooling system is struggling to keep the temperature down.
The cooling system on a V12 is capable of its job if its kept in good condition but there isn't much leeway if something is wrong.
I would suggest a thorough go through the system. As a starting point (and I'm sure others will chip in too)
Is the radiator in good condition? Look for damaged or missing fins
Is the radiator obstructed? Look for a build up of material that may be preventing airflow. Also look between the radiator and aircon condenser where debris can get stuck
Is the system sealed properly and air-tight? Look for leaks where coolant can escape under pressure and air can get sucked back in as it cools
Does the atmospheric recovery system work? Look for leaks and blocked pipes
Has the system been emptied, flushed and refilled with new antifreeze regularly? Ideally this should be every 2 years with the radiator taken out and flushed.
Are you sure you got all of the air out of the system when you changed your top hose?
It sounds to me like it may be time for a cooling system overhaul. If it hasn't been done for a while then its a good investment in your car's longevity and reliability and within the scope of a home mechanic.
Sorry if any of this sounds apocalyptic! The good thing is the worst hasn't happened yet and you've caught it in good time.

PS good picture! Where is that?

[al.sharp1]

I appreciate the great response David. Clearly a bit of work to do! Pic is at Kessock Bridge as the A9 passes Inverness onto the Black Isle. Part of but not the official route for the NC500.

[al.sharp1]

Just had a closer look at my radiator and its not in good condition. Wondering about replacement. Jag rad is c£800. Any views on ASI PRO PERFORMANCE AA5052 aluminium radiator - or alternative suggestions?

[davidr]

My suggestion would be to have the existing radiator re-cored. You can have an uprated core fitted and you'll have the reassurance of knowing that it will slot back into place with no hassle. Almost certainly cheaper too.

[al.sharp1]

Thanks. I'll look into that. As a followup - any recommendation for best antifreeze/ inhibitor?

[SimonR]

Pic is at Kessock Bridge as the A9 passes Inverness onto the Black Isle. Part of but not the official route for the NC500.

I think I may have seen your car parked down there, outside the Costcutter in North Kessock last summer when we were up there on holiday, if it's a regular haunt of yours. There was certainly a very nice red V12 XJ-S convertible there anyway! We often venture up there to stay in a holiday cottage in Kilmuir, just round the other side of the bridge, on the Black Isle.

It used to be a good holiday to take the XJ-S on so we could stretch its legs on those beautiful roads out towards Gairloch, but the arrival of our daughter three years ago has put paid to that for now. One day I hope to do it again.....

Hope you resolve the overheating issues with your car - I'd also agree with getting the existing radiator re-cored by a specialist. These guys near me are very well regarded:

http://www.angliaradiators.co.uk/

Although I assume there'll be someone else a little closer to you than that!!

[al.sharp1]

Thanks for response. Yes it is indeed a local haunt for me so more than likely to have been my car. As it happens, I was on the Gairloch road last week - not in the XJ-S though. Turns out Precision Engineering in Inverness will recore mine so that's my current plan. Just have to get it stripped out now!