Hi Vector,

Thanks for your reply, I wasn't trying to be cranky with Mikey - people on this forum are great and a I really do appreciate all the great advice people offer. I understand that temperature fluctuations are normal and that the car will get hot at times depending on the circumstances.

It's clear there is a problem given that every time my car is stationary it starts to heat to the point where the gauge hit 220*F plus (and other symptoms mentioned in above posts) in less than 30mins. Ambient temps here at the moment are about 20*C/68*F. Other threads indicate that at 220*F it's time to start getting concerned. So I am. It's not like it's happening when the cars been working hard on mountain climbs on twisty roads or being driven hard like, err...a sports car (which I don't). It will happen if it's parked in my driveway idling, the temp climbs and doesn't stop.

I guess I'm not really asking if the car is overheating but trying to understand what is causing the overheating. I'm replacing the thermostat today but noticed how the AC being off resolves the problem completely and wondered if that gave any clues as to additional/other problems that might impact on the efficiency of the cooling.

My car has the recommended WSS M97B44-D coolant.

 

Are the fans turning on and off at the correct temps?

Idling an engine for an extended period will cause just as high coolant tmps as going up a long grade. Having the AC on while stopped makes it worse.

 

If both fans spin as required, it is likely not the fans.

If the engine cools rapidly once underway, it is a sign that the
water pump is on the way out. The increase in engine speed
allows the pump to push more volume.

The pump is easy to change, and not expensive.

As for the behaviour when the AC is turned off, that is
consistent with volume considerations.

 

We're back to my post #2.

 

Have you checked your thermostat yet?

 

. . . and my post #4. I think 220* is too hot!

 

Many engines frequently achieve this temperature, in accordance with their design parameters.


The days of running a Chev SBC at 160 thinking it made 'more power' are long gone.

 

Thanks for everyone's responses :-)

With everyone's advice, docs and sticking my head into the engine bay I feel like I'm starting to get to know my car.

I replaced the thermostat yesterday (topping up with the spec'd coolant). The bottom 5 inches of fins on the radiator were clogged so I cleared that out.

I haven't had a chance to get test much yet, but all is working correctly, fans spun up at about 95*C / 203*F.

If it still gets unreasonably hot I will, as mentioned originally by RJ237, replace the waterpump.

I'm not planning on it unless I have to....but what's the minimum I need to remove in order to get to the water pump?

By the way, is there a special tool to remove that coolant filler plug on the top of the engine? I couldn't find anything at my 2 closest auto stores, however I had a spark-plug puller that was exactly the right fit...but just wondered.

Thanks everyone!

 

If you mean the hex key for the top of the thermostat tower, DON'T. That old plastic cap will probably crack. You can refill through the reservoir. Some have removed that cap by carefully using channel locks, but I wouldn't risk it.

 

Hmmm, mine has a metal plug, you can see it in the image below. I was just following the guide for draining/refilling the coolant guide.

 

Yeah, the XKR had a metal thermostat housing while the XK8 had a plastic housing and cap. The many year old plastic cap could be easily broken by using the obvious 10mm Allen wrench socket in the top. If you don't have an Allen wrench to fit your metal cap use a hex bolt that the head will fit and add two nuts to create a substitute.

 

The plug in this photo is NOT the primary fill point for the supercharged vehicles. The black plastic reservoir is where you fill the coolant. AFTER filling the system via the resevoir, this plug is used just to top up the intercooler system. The connection between the systems is just a very narrow vent pipe.

 

Yep, didn't think it was WhiteXKR, however the drain/refill procedure clearly state that it should be topped up during a complete fill - presumably to help remove any excess air for the system.

 

Not thinking again, forgot you have a XKR. That's a 19mm. I bought one online.

 

...actually, it's an XJR...but I'll let it slide this time

 

Before changing anything, I would pull out the radiator, (about a 15 minute job), and check to see that there was not a build up of debris between air conditioning condenser and radiator. That was a problem on a ford that I owned. Also flush condenser fins with hose, check radiator fins are not clogged. Are both fans running at full speed when the car gets hot. Are you running coolant at the moment, it stops corrosion, "wets" the metal so it transfers heat more efficiently, and raises the boiling point.
keep us posted.

 

This is the thermostat you need, the others that you looked at were earlier models, and too small.
Tridon Thermostat Jaguar XJR V8 AJ30 Mpfi X300 99 03 | eBay

Looks like you can get it from supercheap.

Is the undertray still fitted to the car, it is a piece of flat plastic, the width of the car, running from the spoiler to the front of the engine. Its job is to stop the hot air from the radiator being drawn back into the air inlet again.

 

Hey Freddo,

I ended up getting one from Karcraft (Silverwater) who delivered it next day cheaper than Supercheap (without postal charges). The car coolant was already the 50/50 specified, so I just topped it up (well, replaced over half of it) once I'd changed the thermostat. I also cleaned out crud from the radiator - not that much.

I can't see the plastic undertray, unless I'm expecting something bigger than it is - how big is it? Obviously as wide as the car - but how long? There something attached to the plastic spoiler about 20-25cm deep?

I haven't had a chance to really test it again yet but will do this weekend.

I'll keep you posted!

 

Here is an indispensable tool for heating or over-heating problems at about the best price I have seen. The temperature reading at the data port is, like the OEM temp gauge, an approximation of the true engine temp based on the temp/resistance ratio of the sensor. Without the ability to measure the actual temp of the engine directly you do not know if the issue is a sensor or something else. It took 3 new sensors before I found one that almost matched an IR gauge reading.

Non Contact LCD IR Laser Infrared Digital Temperature Gauge | eBay

 

Excellent, I've just ordered one :-)