It's a little hard to find the expansion tank for the '99 Jag online so it's hard to tell how much the parts alone cost, but id imagine it would be anywhere from $70-$180. If so it seems reasonable, even cheap to fix for $300

The leak is at the point where within 3 minutes the entire tank empties out from the bottom. Water trickles down, rather pours out, around where the passenger side catalytic exhaust (im not sure if thats what its called) is

 

That was the root cause to my old engine blowing out the head gaskets. Good thing you caught it in time. Check your PM again.

 

I attached some photo's below.

 

those parts actually do seem similar, these are what mine look like
Any second opinions?


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The picture isn't working, but this British parts store on eBay has it listed for both models. http://www.ebay.com/itm/Jaguar-XJ8-X...a09609&vxp=mtr