I've had some very sporadic overheating episodes that I think are due to a stuck thermostat, so I'm going to try replacing mine to see if the issue goes away. I did a search and the OEM housing seems to run about $100-120 while aftermarket ones are all over the place with a couple of aluminum versions available on eBay and Amazon. I'm assuming all of the aftermarket ones are made in China like this one I found on Amazon:

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Kind of hard to pass up at this price. Has anyone here tried something similar?

 

. Problem is that OEM is crappy short lived plastic but made and fitted specifically for our cars. Aftermarket metal could be just slightly off its specs and cause havoc. It could be a toss of the dice. If we had years of feedback of those using the metal aftermarket pieces on our limited production cars we’d have a slight edge on the decision making. Unfortunately Jaguar has made some horrible decisions on cooling engineering ( not to mention no temp gauge) and materials chosen for suspension boots.

 

I understand the sentiment. Plastic prolly used primarily to reduce weight and meet various government mileage specs. That said, it's a 12 year old car and 12 years is a pretty good run for that part. Sure, it's not the old days many of us are used to but still not bad. @Simon Tan , if it were my car, I would use OEM. $120 is nothing in the scheme of things. I'm still on my original housing and stat.

 

More likely plastic is/was cheaper than anything else. It's always about the money.

 

And it needed to last longer than the warranty period.

 

Based on experience and knowledge, I'd stick with genuine OEM plastic. First, genuine JLR is only about double this price, second aftermarket parts often don't fit as well as genuine, leading to further issues, and finally plastic does not respond to heat the same way as plastic which in this application could potentially affect how the thermostat operates as well as affect ECT readings. I had the original thermostat last about 150K miles before one of the seams began to seep, but not leak. For $100 the risks far outweigh any benefits.

 

thermostats are the lowest concern item on these.

crossover and the heater manifold are 100000x more likely to leak

that being said there was an entire bad production run last year on the OE 133/126 thermostats. they had to put a stop sale and return TSB up on them

 

. Order of failures 1) water pump 2) front crossover 3 ) thermostat housing 4) rear crossover/ heat exchanger 5) everything else. If any of these parts ( especially front crossover and rear crossover ) ever have a catastrophic failure as in splitting etc, our engines are toast. Everything else can eventually start seeping which can be maintained by constant checking levels before every drive. Most of our cars seep, but failing and great loss of fluid at one time is the fear. Best to change everything or at the very least the 4 most vulnerable plastics mentioned. Keeping a regular eye on coolant level is the safest way to keep going. Our cooling system is the weakest link to XK ownership. Great car but crappy cooling system.

 

I have an ongoing over heating issue, the problem with these cars as I see it is pin pointing the issue. At motorway speeds and basically normal road conditions my car sits happily at around 91 degrees C. As soon as I hit traffic or any length of stationary traffic the temp goes wild. I know the main water pump is working fine, I’ve had the electrical supercharger pump changed, I have fitted a new metal stat housing and new stat. I believe my issue is the electrical radiator fan not working as it should. I am currently waiting for a new one, I have witnessed the speed signal for the fan being at 40% and yet the fan was stationary. So you’d think that would definitely be the fan motor, but it might be the ECM control, or the wiring harness. I am a skilled industrial electrician but this fault is doing my head in!!

 

I found this website very useful for the 5.0 SC engines


Guy seems very knowledge and honest.

 

Just a note to get the right thermostat housing. There are both sensor and no-sensor versions.
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