I've searched and read several threads, none seem to cover this. My apologies if I have missed the correct one. Here's what I know:
1998 XK8 convertible
Lost serpentine belt and got hot (not overheated to red zone).
replaced tensioner and idler assemblies and belt
with the help of a mechanic (non Jag specialist, but familiar (allegedly))
Pulled all spark plugs and cleared aspirated coolant, and replaced spark plugs.
Drained coolant from radiator and flushed with clear water
replaced coolant (at overflow tank up top only).

Ran at idle for over 45 minutes with heater both off and on at various times, no leaks....

Drive it down the road for 5 minutes, and low coolant light..
Home: something is leaking coolant towards the left center at the rear of the motor.
It is not coming from the overflow tank, and the "octopus" doesn't seem to be wet. It does appear to be almost directly below the throttle body, somewhere (ish)

Is there a chance this is due to air in the system from an incorrect refill / burp process? It's not a constant drip, not even with the thermostat out. I cannot currently get under the car to look from that side, but am not sure what to look for even then, or how to correct.

 

could be a couple of things - 3way-connection under throttle body, heater hoses. Best thing is to pressure test the system and see where the leak may be

 

Thank you, sklimii. Unfortunately, I don't have the tools to pressure test at the moment. I plan to get her up on stands tomorrow evening and attempt to see, it looks like enough flow that the location should be visibly clear, I simply cannot see if from above. I'm still curious, however, if this could be the result of failing to follow process on the coolant flush as well.

 

I don't think it had anything to do with the coolant flush, more likely overheating resulted in a hose or connection failure.

The temp gauge will not necessarily go into the red when you overheat, another jag gift.

Do not run the engine with the thermostat removed, it's important for maintaining proper coolant flow to various parts of the engine.

 

Are you absolutely certain the Expansion Tank isn't the source? These are known for pinholes or splits on the joint which only leak when hot and under pressure.

The cooling systems hoses are visible without any dismantling apart from the pipe from the Expansion Tank to the Atmospheric Recovery Bottle.

If it's a persistent leak with no visible source then it could be the one of the 'valley' hoses to the heater.

Graham

 

I'm sure it's not the tank with the cap where you top off... It's below that.. I'm NOT sure it's persistent, as it doesn't seem to do it at all if you just let the car idle (well over an hour at this point).. but you get in and drive down the road, or run up the RPMS, and she lets a pretty good leak. I'm going to pick up my Jack stands (I moved, they're at my old house, now used by my son).. and try to get her up high enough to crawl under this weekend... I've seen the diagrams and pictures of the valley hoses, but where is the atmospheric recovery bottle?

 

Here is a diagram where the recovery bottle is located


Here is also a link that might help as to where you can find it.
https://www.jaguarforums.com/forum/x...ocation-57551/

 

OK that's not where it's coming from. I guess this evening and weekend are going to be spent accessing the valley hoses and the heater core hoses, if not one and the same. Ugh. Hopefully there won't be too much of a wait for the parts!

 

The Atmospheric Recovery Bottle feed pipe goes across the vehicle behind the engine (the ARB is behind the RH wheelarch liner) so it is still a possibility.



Note that the overflow pipe is much closer to the centreline of the vehicle.

Graham

 

OH! That's on the (US) 'Passenger' side.. opposite side of the expansion tank. Given the semi-intermittant nature, and that this seems to happen during higher RPMs, that's a great place to look.. particularly that hose!

 

Finally got all the hoses in house and replaced! Markedly easier job overall than I had feared. Unfortunately, I've managed to unhook (or I failed to plug up) the vacuum hose running from somewhere under the intake manifold up to the left side cover, so I have a rough run and horrible sucking sound.. lol. I'm hoping to figure out where that plugs in without taking it all back apart!

 

Everything is re-assembled and the vacuum hose located and hooked up for no more hiss. Now it's running extremely rough and throwing up "restricted performance" with the amber check engine light. I don't yet have a code reader, but knowing that it was running well *except for the coolant leak before disassembly, and that it's running rough now.... Is there a torque spec for the air intake manifold? I put all new gaskets on that, but couldn't find anything giving me torque numbers. I just tightened it down good and snug with the ratchet. There are no apparent cracks or leaks in the breather tube running to the throttle body... help? I really don't want to give up and send her to a shop. *and I don't have the $ right now for a code reader...

 

Get an ELM327 from eBay, and pair it with a phone app. It's like *$ coffee money...

 

Wow, thanks.. Done, it'll be here Sat... Meantime, anything else I can look for?

 

Misfire on Cyl. 8... Resolved! Coil pack was wet from spillage on coolant fill, and the cover wasn't fitted correctly. (not part of previous work, so who knows how long!)