My coolant level was running a bit low. When I opened the hood I noticed some fluid, (turned out to be coolant), puddled on a cap on top of the engine. There are water lines running into this cap from the rear resovoir.
The cap seems to be removable by a hex drive of sort. What is this cap?

I am certainly no mechanic and need any help I can get. With the coolant about a cup low, I knew it must be somewhere. I will pressure test the system in the next few minutes but I already believe that it is coming from this "cap".

Thanks

 

I think you're describing the Thermostat Tower.



This has a black plastic cap (Item 3 in this drawing) with a hexagon in the centre. Please confirm and I'll give you the information on it.

Graham

 

Thanks and that is what I'm looking at. Could it be that the cap is cracked or could I have a bad thermostat? Any suggestion?

 

The Thermostat Tower is a known issue on the V8's.

The OE Jaguar plastic Tower can crack leading to coolant loss. A regular upgrade is to replace this with an aftermarket aluminium Tower. This is the original (left) and replacement (right) on my 2001 XK8 but I had to do the same change on my previous 2001 XJ8L:



Does it appear to be anything more serious than a leak from the cap?

Graham

 

At 1st glance it appears to be from the cap itself. The coolant is coming up through that hexagon centre. We just dried it out and I'm going to run it around the block and get it hot and look at it again to be sure.

Would I need to replace the entire housing as I see in your picture or just the cap? And where would be the ideal place to order that from? And also, what would I be asking for exactly?

I really do appreciate your help on this!!

 

Here's the Parts Manual diagram and the Part Numbers:

JAGUAR X308 - Thermostat & Water Outlet.pdf

You'll be lucky to get away with only a cap and seal leaking. However, if this proves to be the case, these parts are available separately both from Jaguar and aftermarket suppliers.

The odds are the Thermostat Tower will need replacing and, if so, it's prudent to swap the Thermostat at the same time as these are also a regular fail on the V8.

As you can see from my location, I'm a long way from Georgia! Any advice I can give on parts sources won't help.

Now you've discovered exactly what the issue is and what's required to fix it, a question posted on X308 section asking for US suppliers is the best option.

Graham

 

Thanks and once again, I very much appreciate the help. I'm sure you've saved me a lot of anguish!!

 

I had to replace the whole unit. The bolt was stripped so I could not replace the thermostat. Had to drill out the bolt then install new tower. At the same time I did a rad flush and installed new water pump.