I think I solved my squeeking belt syndrome. I found the leak of coolant at the joint where the lower expansion tank hose (about 1" hose) fits onto the expansion tank itself. I looked underneath the expansion tank with an inspection mirror. The drops of coolant that appear come out of the area where the spring clip is at the joint for the lower hose to the tank nipple, and NOT the white plastic area. This leads me to believe that this joint is not sealing well. I concluded that the expansion tank itself is probably ok with no cracks, since there are no drops forming at the bottom of the tank where the nipple is.

Is there an O-ring inside that I can replace or do I have to replace the whole hose? Anyone have a part number for 04 XJ8 for the o-ring or hose? Thanks.

go to the dealer and get the green oring for an ac compressor. do not get the black 1 it will leak again. take the spring clip all the way off with pliers and dont drop it. using a small pick take out the black 1inside the black hose connection and slip in the green 1. lube up the expansion tank lower fitting, slip the spring all the way back on then push the hose connection back on till it clicks

Thanks Brutal,
Got a matching new oring at NAPA....problem fixed.

I actually had another coolant problem. The thermostat housing was cracked (housing between intake manfold and thermostat) and leaking coolant all over the belts. Why did they make this out of plastic?? Anyway the entire new thermostat assembly (with stat, sensor, all housings pre assembled) was surprisingly only $105 at the dealer. Took me about 3 hours to install. had to remove all the throttle body stuff to get to it.

Well give the 2 Kens at Motorcars alittle time and they will come out with a pot metal housing for the later V8's like they did for the older ones

Brutal, do you know the exact size o ring for this? Mine must've slipped out when I was changing the expansion tank, so I don't have one to compare to. I'm in desperate need and the dealer parts dept. isn't open til Monday. I have a 2005 jag s type V6.

Steve, not sure if this is the same location, but might be. I have a 2004 xjr with the expansion tank. Had to replace the o ring inside and it all seems to be working fine...got it at ACE...mine was black...

https://www.jaguarforums.com/forum/x...2/#post1358928

Hi fellas, 2007 xj8l, I had the nipple break off at the upper refill hose. I cobbled together a patch with vacume hose parts and duct tape. Everything was fine while I waited for the new reservoir tank. I just finished installing it, filled her up and started it up only to find a coolant low warning. Let it run for 20 min, checked the coolant and it's full. Any ideas?

Sticking float in new tank.

Sensor wiring problem.

Sensor fault.

Thanks, I'm thinking king the float is most likely. The sensor and wiring were all in working order prior to replacing the tank and there doesn't appear to be any wiring damage from the repair. Does anyone know how to check that without removing the whole tank again? I'm not that great a mechanic

I have a spare tank and the float rattles about when I shake it.

Did your new tank do that?

Did you change the sensor from the old tank to the new tank and did you plug the

wiring in?