Water Temp shortly before Red on steep mountain roads

Hello everyone!

My daily 1994 3.2 Auto Xj40 is getting a bit hot when driving on really steep roads for about 20 min and with outside temp of around 30 degrees celsius. Temp is then shortly before red. Is this normal? The electric blowers where running around 4 minutes after I turned the engine off.
I got my radiator flushed with new coolant and I also got a new thermostat.
Is this normal or should I replace my radiator. Car has around 250 k kilometers on the clock.

Thank you for your help!


No, it isn’t normal getting that hot, although having fans run after shutdown is pretty normal. You should check the space between the condenser and the rad for bits of crap and general blockages.

Undo the torx bolts on the upper rad support and lift off the plate, that will give you access to the gap.

That and maybe replace the thermostat.

I already checked the space, it was pretty clean, and there is a New Thermostat and i flushed the radiator

Was it doing this before you did the flush, stat, etc? Or is that why you did the work on the cooling system?

That s why I did it. because on steep mountain driving and hot outside temp its going up, shortly before red. Maybe its normal under this extreme conditions?

Is the coolant level in order and does the coolant look good, as well as the oil? With the engine cold, is there pressure on the hoses immediately upon startup?

I‘ll check this. Oil is new as is the coolant.
Maybe the radiator is blocked? I had a similar situation with my xjs. But this case was much worse: it did overheat. I replaced the radiator and since then everything was good!
Where do I get a radiator replacement? Here in Europe its very difficult to get…

Could also be a collapsing hose on the suction side. I would avoid blaming the radiator as long as possible but you would find a replacement eventually.

Screen Shot 2021-05-25 at 10.42.54 AM
aybe your gasket looks like this and there’s no water flow through the head

My xj40 overheated when the air conditioning was working. It was enough to wash both radiators from the outside, blow with compressed air and use a radiator cleaner.

A bit of history: back in my factory warranty days with the XJ40 and XJS we had some issues with internal clogging of the aluminum radiators. The blame was put on non “phosphate free” antifreeze use. Some of which might have even been installed at the factory. Jaguar in the USA, then began supplying their own branded antifreeze that was phosphate free. Not sure if today all antifreezes available on the market are phosphate free or not, or dealers still supply Jaguar approved antifreeze. . Can the end tanks be removed from the aluminum radiators and have them rodded out like the old copper ones could?

After getting a leak in the oil cooler, a couple years later mine would overheat. Turned out the radiator fins had been coated in oil from the original leak and over two years time, collected enough dust to block the fins. Hard to see just casually looking at it from the front

I don’t think that is normal. The cooling system was extensively tested under conditions you describe for millions of miles when the car was under development. If everything is in good condition the gauge should remain around the ‘N’ position despite outside temps and hills etc. Although radiators can become blocked internally, if you are certain the air flow through the radiator is good I would check the entire system before condemning the radiator for being blocked. As already mentioned check all the hoses to see if any have gone soft and could be collapsing internally when hot. Is the pressure cap seal in good condition ? Is the drive belt to the water pump slipping, does the pump feel free to turn and without any rocking or free play ? Is the transmission oil up to the correct level and in a good clean condition ? Does the car coast freely in neutral when it’s hot to rule out a brake caliper sticking ? If all that checks out as good condition try removing the radiator and back flush it by turning it upside down and using a hosepipe sealed around the outlet, if you can, use a radiator flushing agent and leave it over night before the back flushing.

Clemens …

If you’re experiencing overheating on a car almost 3 decades old I think putting in a brand new radiator is something that you OWE it ! Forget getting it cleaned or rodded out, show your Jaguar some respect AND possibly stop chasing your tail on your problem.

That’s one way of looking at it Grooveman, but what if there’s nothing wrong with the radiator,
then he’s still ‘chasing his tail’ after replacing a perfectly good radiator. As you mentioned the car is almost 3 decades old, that’s why I suggested he inspects the entire system first.

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Casso …

Of course the other way to look at it … if it hasn’t been replaced in the past there’s no way a radiator that’s been used for 27 years and 155,000 miles is going to be as efficient as a new one. Since they’re not that expensive think of it as a routine maintenance item. I’m not a fan of troubleshooting by blindly replacing items but since engine cooling is so critical I’d start by replacing it and have one less thing to worry about.


Regardless, you’re absolutely correct that the entire system should be checked

Grooveman I have to agree a radiator almost 30 years old is bound to be down on efficiency and changing it would be a sensible move, but Clemens mentioned getting a replacement in his location was very difficult, that’s the only reason I suggested he tried leaving a flushing agent in it over night and then back flushing it.

Casso …

“I suggested he tried leaving a flushing agent in it over night and then back flushing it.” Very good advice!

Measuring the inlet and outlet temperature would also show if it works well wouldn’t it?