Temperature in S1 engine bay

Found an IR temperature gauge when cleaning my garage and pointed to my S1 engine bay in different parts as shown in picture, after a 30 mins drive:

A: 310~320 degrees
B: 282~292 degrees
C&D: 88~96 degrees
E: 98~102 degrees
F: 86~90 degrees
All measured by the handheld gauge in Celsius and just after engine turned off. Are these numbers normal?

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Why wouldn’t they be normal. Maybe the front carburetter is leaner than the rear, maybe the IR gun isn’t perfectly exact (they work best on dull black surfaces).

Oil is hotter than coolant and the head is cooled more than the timing chain area. 90° degrees at the radiator are too high. Do you have any problems with it running hot? Maybe a 88° thermostat?

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I am not sure what type of thermostat is used in the car. I may get one 78° thermostat to fit in by myself.

Another question-was the engine running when you took the measurements or did you turn it off (which would explain a much higher temperature in the radiator due to heat soak)?
And what was the ambient temperature?

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Oil can become hotter than coolant during high speed running but in slower traffic the coolant is as hot or hotter. 90C is not too hot for glycol mixture at 7 psi in average driving.

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All temps were taken just after engine turned off, maybe in 5 mins? It was about 25 degrees.

Yep, I forgot about that the coolant is pressurized.

No, it’s not too hot, but for water that has already moved across the radiator on a car that’s been idling for a minute it might be a bit much if it’s at least ten degrees hotter than the operating temperature? That was my thinking.
With the car standing for five minutes, 90° is perfectly fine. The heat that’s been in the engine had time to soak into the water and is no longer carried away (the pump is shut off, but the engine is still hot), so it reaches a much higher temperature at the highest spots.

I thought the oil was even hotter, but if it depends, it might be alright. The measurements all make sense to me, then.

My series 3 shows 105-110° on the gauge a few minutes after shutdown. Nothing wrong here!

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Provided everything is behaving normally there is no issue. You have more data than most people so there are few comparisons that can be made and even if others have info there are technical measurement and usage variables that would make direct interpretation risky. Enjoy that car.


Thanks gents. It just surprised me abit that the exhaust manifolds got north of 300 degrees. I never measured the temperature in my other cars since they are all covered by some plastic.


They get hotter than that :slightly_smiling_face: Taken after an hour @ 130kph, with heat shield, in the dark. All my cars glow, but most need higher speeds than that to be visibly glowing.


Wow, I have only seen something like this on those youtube engine dyno testing videos.

I’ve seen an engine on a dyno once (at Eberspächer probably, so probably any standard turbo Mercedes or BMW…) and they were glowing bright red just like in the videos, I can’t even match that when pulling up after full power. Amazing what the steel can cope with. Beautiful sight!

The hardest pull I could put on the engine is when doing hillclimb. I leave it in 2nd gear so to maintain the rev at 2500~4000rpm through the whole 30~40mins. But feel more pressure is on brakes rather than the engine. I will test the temperature next time after hillclimb.

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You will have a nice clean engine inside. Many Jags (especially V12s) are not used hard enough and die of black sludge and neglect.


The exhaust manifold temp is not so surprising given the temp of exhaust gases. Still it is fairly high. To protect surrounding materials - we were talking about crispy connectors and wires recently - Jaguar put a stainless heat shield over them in XJ cars which seems to be missing in your car.

I’m a bit surprised about the higher temperature of the front exhaust manifold compared to the rear. If anything I would have expected it to be cooled better by the fan than the rear exhaust manifold. So you might cross-check plug faces.

The other thing surprising me is the temperature taken at the expansion tank at the left wing - if that is what was measured as “F”. I would have guessed water getting there should have cooled down considerably … but I didn’t look at the place where the water tube leading to the expansion tank is coming from.

Apart from that: just about any exhaust will be red hot with serious driving - just as brake rotors do with serious braking. Yet, they are up to it.

Good luck


75 XJ6L 4.2 auto (UK spec)

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Looks like the radiator, but I‘d expect the tank to be this hot too (it receives the hottest water after shutdown, when the water expands a little further into the expansion tank).

Not sure if his had the heat shield or this was optional, don‘t know the AED. The front manifold can be hotter for many reasons, plugs/AFR or temperature while running are the only diagnostics I would accept.

Keep in mind that the car was shut off for a couple minutes; as Peter said, enjoy the car! Hill climbs are great.

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Yes, the USA 71 I owned at least had the heat shield, plus a duct from the exhaust side to the intake, which was fit to the heat shield. You can see in the OP’s photo the tapped holes for the heat shield in the exhaust manifolds, and the tapped hole for the crossover in the cam cover.

I was very concerned about heat soak after my daily commuting run years ago. I removed the heat shield and things got a lot worse. I finally fitted louvres to the bonnet, and that solved the problem completely. For good measure I fit a Series 3 radiator and other bits. Besides heat soak after shutdown, I was worried about OP and oil temp (had a gauge). At traffic lights in 100+ deg F weather, the OP would drop in proportion to how hot the oil was. Probably didn’t need any of the modifications, but it was Shipwright’s plain and simple.

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Thanks Jochen.
I have seen heatshields more on series 2 or later cars. Now seriously thinking about buying one or making one by myself.
“F” is on metal area of the radiator. I measured overflow tank and got about 60~64 there.

I had thought about putting louvres on the engine bonnet as well, nut could not find any one doing this in Brisbane area.