Hi everyone , recently a new lurker and new member. First post. Car with questions is a 2004 XJ8 4.2 N/A 70k miles. A few days ago I poked my head under the hood and noticed what seemed to be a slightly low coolant level. I added about 6-8 oz of OAT in expansion tank. A couple days later after using the car I noticed a small puddle of coolant about 4 inch in diameter under the car. I pulled the belly pan and was pretty wet mostly on passenger side and center. Started looking around and wasn’t sure where this expelled from. It doesn’t appear to have an obvious overflow hose or catch tank. I have been driving it sparingly and close to home while keeping a close eye on it and it hasn’t repeated itself in over a week of daily use. I didn’t notice anything under the hood that looked as if it sprayed erratically everywhere. I’ve done some investigating and noticed some weeping at passenger thermostat outlet flange. Which leads to the face of the block and around the water pump. It looks like it’s been leaking for a little bit and haven’t pinpointed it to the water pump. I’ve since ordered thermostat housing, water pump, idler, tensioner, belt and passenger upper radiator hose which was swollen. All thanks to the help of reading through all these fine threads at Jaguarforums I’m still stumped where that large amount of fluid came from and can’t replicate. I did look at things much closer and noticed the swollen passenger upper radiator hose which does connect to the thermostat housing and noticed it looks as though it’s moved on the radiator inlet about a quarter inch as though trying to slide off. That hose does get hot and firm and also does become relaxed when cool. I have bled the system several times and it doesn’t seem as tho the coolant level in the expansion tank fluctuates as far as I can tell which I thought odd. I do have heat in the cabin. I can squeeze upper and lower hoses of the radiator and hear slight clicking and clacking of what I believe the actual thermostat All other hoses look good and dry with no discernible swelling. I know I have quite a bit of work ahead of me and will keep posting any revelations. Thank you for any and all thoughts.

 

You might chect the radiator on the passenger side for stains, just in case.

 

That's not from overfilling, it was already leaking somewhere which is why you had a low level.

Common sources are cracks in the radiator side tanks, usually right at the hose pipes, or the thermostat housing. The expansion tank itself can crack as well. Finally, it's VERY hard to see with all the hoses installed, but it could be the water pump.

I've just been through a cooling system overhaul this past summer, which started with a crack at the fitting for the upper hose on the radiator side tank. I changed the radiator, but it was a helluva job! The A/C lines wrap around the top of the radiator and create a very restrictive space to wriggle out of and back in. Once the radiator went in and the system came to pressure, the expansion tank cracked, and then I had leakage from the water pump. I went for a complete overhaul, including all hoses. None of my hoses were actually in obvious need of replacement except the one under the intake manifold, obviously the most difficult one to reach, and that one was soft and ballooned. Sourcing the proper hoses was difficult, and I ended up never finding the one that attaches to the bottom of the expansion tank so I reused my existing one.

 

Wingrider- thank you very much. I just went and checked and super dry with no stains of any sort and a light uniform (undisturbed)layer of road dust.

 

Wfooshee- Thank you very much. I know it has been leaking from thermostat housing and/or water pump but I’ve never had a puddle or an accumulation on the ground until just after I added coolant which may have been a little too much. I forgot about the interior steps of the expansion tank as fill min/max. I definitely overfilled beyond the max step and thus had a small one time purge puddle. Otherwise the leak or leaks I have are mostly contained to running down the face of the block and cling there until evaporation.

The radiator is very dry and no signs that it’s leaked. I have replaced the expansion tank and cap do to the barbed nipple. You aren’t kidding it’s hard to see every nook and cranny as things are shoehorned in there every which way. I am kind of suspect of the water pump but not certain because what I’m certain of is leaking right above it….thermostat housing. I’m just going to replace both.

Wow, I can only imagine the work and frustration you experienced and put into the vehicle. I’m hoping the hose under the intake manifold isn’t bad but you have me thinking that if I’m going this far I should just do it also. I need to look into what’s involved with that now. Thank you for you insight and a reminder to not half *** it and do the valley hose as well.

 

Have a look for stone chips on the front radiator as well as lower part might be even swollen. 300€ for a spare
Coolant tank get fissures way too quickly . Replaced with a Meile 70€.
naturally your hoses are old I do have all the numbers .
If you look down on the reservoir left hand below fixed with one screw onto the radiator is the auxilliary pump.
the thermostat housing is all plastic and broken off pieces can obstruct the free flow of coolant . Jaguar seems to not have them anymore.
underneath the throttlebody is the valleyhose quite easy to get to. More work on the supercharger engine

 

Yeah, I'm gonna call $&*@ on this statement. The intake manifold has to come off, which is not "quite easy," even if it is pretty much straightforward once you realize there are about 137 electrical connectors with three different kinds of locks on them, two of which can't be reached until you lift the manifold and move it forward as far as the wires from those connectors permit. Most places with replacement gaskets have the paper gaskets which are useless, you have to have the metal gaskets with the clips that hold on to the bottom of the manifold to align the gasket when the manifold goes back on. Two of the companies I ordered from pictures the metal gasket and sent the cheap, flat, paper gaskets, which they did accept the returns on.

It seems that on some of these cars, the valley hose goes all the way through to the back of the engine, but on mine it loops back to just under the front of the intake manifold. Maybe the '04 goes to the back and is reachable from up top, I couldn't say.

 

Like wfooshee i also went throught the exersise.
Of thermostat, with housing,water pump, auxillary pump.
Radiator, with all the hoses, including the valley,.
The two short heater hoses in back.
Are only available with the metal pipes attached.
Will have to find replacements other than stock for them.
When i do the 07 hoses will see if they will fit the 04 or not.

 

the one going to the back of the engine is the super charged engine

 

That's what I was thinking, but then, how is the hose easy to access? You CANNOT get to the end in the valley with the intake manifold on the engine. I don't think you just can unbolt and raise the manifold far enough to clear, at least I couldn't.

Not trying to argue for the sake of argument, just thinking we have different definitions for "quite easy..."