Most manufacturers calibrate the gauges so the needle is at or near the middle of the scale when 'normal' temperature is reached....which is typically thermostat rating. That is, if Jaguar used an 88ºC thermostat (which it did), the middle of the N would be about 88ºC.

XJS gauges are known to be a bit flakey, though, so the middle of the N on one car might be xxx-degrees but something quite different on the next car. On my XJS, middle-of-the-N was about 88ºC as I recall, and top of the N was about 93ºC.

Anyhow, car-to-car variances aside, it's safe to say, IMHO, that if the needle touches the N at the top, bottom, or middle....then you're in "normal" range. That is, nothing to be alarmed about. For example, there's no reason whatsoever to think that running at 93ºC will hurt the engine in any way.

Understandably, sort of, we're hyper-sensitive to coolant temps on the V12 Jags. But, some of this sensitivity is misplaced, IMHO, and came from the words of one particularly noted and respected XJS owner who insisted that ANY increase in coolant temp above thermostat rating temperature (and corresponding rise in needle reading) was "overheating". In strictest terms he is correct...but it causes lots of needless worry.

This is the exact reason that Jaguar finally threw in the towel and joined the ranks with so many other car builders who have coolant temp gauges that are calibrated to stay firmly in the middle of the scale over a wide ** range ** of temperature. For example, my XJR temp gauge hit the "N" at 174ºF and stayed there until at least 205ºF. I say "at least" because I never recorded any higher temperature.

Cheers
DD

 

I would recommend you buy everything online, and do a little research. Often one part will be a better price at one place, while another will be more. Also take into consideration shipping costs from each seller - Terry's Jaguar, Coventry West, SNG Barratt, XKS Unlimited, Jagbits, etc.

Also some parts aren't only used on the XJS, such as the fan clutch which can be found lots of other places. I've had great luck using Amazon, RockAuto, and eBay as well. Careful shopping can make a huge difference in $$.

Make a list of everything you might need (remember copper crush washers, gaskets, and so forth) then order everything and have it on hand when you are ready to attack the job.

btw, if you have an ACE Hardware nearby they stock the A/C Insulation foam that Kirby Palm is referring to.

 

Thanks for all the suggestions. I opted for the Wizard unit thanks to its drop-in application. Also getting a new fan blade (obviously) and clutch. I'll let you know how it goes.

Jess

 

So, update:

The Wizard unit (even though I ordered for the V12 XJS with automatic transmission) apparently arrived with an extra hole in it for a temp sending unit. And, we're having trouble locating a suitable temp sending unit that won't cross-thread the hole (we just want to plug it up). Anyone ever run into this before and/or can suggest a fix?

Jess

 

Just ask Wizard the thread size and buy a plug and a fibre washer to seal the hole? Some later cars had the electric fan temp sensor in that hole, I believe.
Greg

 

When I received mine, I had ordered a temp senor for it and the plug...
I could not use the temp sensor as the stock fan shroud did not give enough clearance for it


Jaguar XJS V12 Auxiliary Cooling Fan Switch Upgrade


now a lot of people here do not like this guy so I know that posting this link is going to rain some stuff down upon me... I never had any problem with him, ordering receiving paying or what ever...


I got that switch and the plug from him... the radiator too... that was shipped straight to me from Wizard Cooling... (I paid a little more than if I bought it straight from them but hey Knowledge is power and money)


I think you can get that plug from any hardware store... even Lowes...
I just wrapped mine w Teflon tape and tightened it up... OH I knocked everything (shroud) down to bear shinny metal and painted it all black

 

Start from the basics: Fan and clutch are good and pulling air? Rad is clean inside and out? Mine started overheating and when I pulled the rad the fins were plugged with sand ( originally sold in Florida - owner must have lived near the beach). It's also common that debris gets pulled in between the rad and condenser and blocks off the rad.

Are the foam pieces in place that surround the rad and seal it to the body? Without that the air will bypass the rad and significantly reduce the cooling ability.

Thermostats are opening and closing properly? You mentioned that needle not coming up to N on cool days which makes me think the thermostats are stuck open. Take an IR laser thermometer and measure the upper hose temps.

Finally, how clean is the inside of the block? I had an E type that overheated and once it was over about 72F outside it became out of control overheating. Turned out the PO has not used used distilled water in the coolant, so the inside of the block was coated in minerals from the water, since we have hard water. I had to do a chemical flush to clean it out, flushing with a hose did nothing.

Drain the coolant, and make sure the block is well flushed. Fill and drain at least 3 times with water until it comes clean. Drain again, then fill with vinegar. Vinegar will react with glycol, so that's why it's important to be well flushed. Run the engine until it's hot and the thermostats open and allow to circulate for a while. Let it cool and then drain both the rad and block. Flush with clean water again making sure the inside is well cleaned and flushed, and then refill with fresh coolant.

When I did this on my E Type the water/vinegar mix coming out looked like milk, there was so many minerals dissolved in it. My drain pan is about 24x18" and I let the water sit in it overnight and in the morning I had a 1/2" thick layer of minerals on the bottom that had settled out. I never had another overheating problem after that, no matter what the ambient the gauge always stayed at the thermostat temperature.

So if everything else checks out, take a look at the inside of the block for plugged coolant passages and consider dissolving the minerals out of it.

 

VW and Audi products used a switch with the same threads for years. Is there a self serve wrecker near you that you could pull one from?

Something like this: More Information for BECK/ARNLEY 2011266

 

https://www.jaguarforums.com/forum/x...er-oem-144173/

https://www.jaguarforums.com/forum/x...o-bolt-150566/

https://www.jaguarforums.com/forum/x...-think-146184/

 

Wanted to give a final update ...

We ended up needing to plug two different holes on this radiator, so "drop-in" is a term that I'd say loosely applies. I wish Wizard would ship the plug that goes on the top driver's side of the radiator with the order. It's a cheap little thing but it cost us almost two weeks getting this problem solved. The other one was much simpler to fix (I didn't even know it had been an issue until I picked up the car).

Having said that, the performance looks pretty amazing at this point. My car lived around "N" to just north of "N" for 3 years, except in the dead of winter. Running the A/C and sitting in traffic would easily get it 2/3 of the way up the dial.

So far, I've yet to touch the "N" zone at all. The car is holding steady around the 1/3 mark on the dial even with the A/C on. So while the radiation might not qualify as "drop-in," it definitely appears to do the job.

Jess

 

Jess,

I wish you had posted that on Friday. I'm in the same boat in trying to find a BSPT plug. What did you do for the other M22X1.5 plug? I've sourced one meant to be an oil plug, as it needs to be low profile to avoid the fan shroud, but it will not be here for another day or two.

 

When I received mine, I had ordered a temp senor for it and the plug... I could not use the temp sensor as the stock fan shroud did not give enough clearance for it


Jaguar XJS V12 Auxiliary Cooling Fan Switch Upgrade


now a lot of people here do not like this guy so I know that posting this link is going to rain some stuff down upon me... I never had any problem with him, ordering receiving paying or what ever...

 

I'm going to claim ignorance knowing the difference between "BSPT" and "M22X1.5" (i.e., which hole is which); for the one positioned on the driver's side at the top, we finally had to get it directly from Wizard. Nothing we ordered locally had the correct thread.

My shop was able to find some generic plug at an AutoZone or Advance Auto to fill the other slot. It may or may not have been from the list of Audi parts someone else suggested to me, they didn't say. Had we struck out on a source for either of these parts, our next step was going to be having a radiator shop weld/solder the holes shut.

Jess

 

BSPT is British Standard Pipe Tapered, which is an imperial thread M22x1.5 is metric 22mm.

Radiators or cooling systems should not use tapered threads as these need PTFE tape to seal them. I said this in a thread yeaterday.

The problem is 2 fold, these plugs are usually supplied with sealing washers, so if the tapered thread is too tight the washer will not seal, so the unsuspecting installer keeps tightening the plug damaging the thread in the process, or the washer seals before the thread is fully engaged. Both of these scenarios have the potential to blow the plug out under pressure.