My XKR has recently developed a coolant leak- it empties half the reservoir and once even lit up the low coolant message. After topping it off and taking it on two (hot and fast) test runs, it dribbled the reservoir back down to half (but didn't flash the message this time). I've held a troublelight everywhere I can top and bottom with it running hot to see if I can tell any signs, but nothing. Any ideas/experience with this? Runs fine otherwise and got all new hoses in the last couple years...

 

The two likely things are the dreaded hoses under the supercharger (hidden, therefore hard to see any leaks) or the octopus hose behind the engine.
I don't want to be an alarmist, but I've read lots of threads (including my own) with the same symptoms, followed by an overheat and a blown head gasket.
Be aware that the temp gauge is next to useless and cannot be trusted to indicate actual coolant temp until it's too late. Read the "RealGauge" threads for more info.
My suggestion is take this seriously and get a shop to pressure test the coolant system to look for leaks before it's too late.

 

In addition to Rob's suggestions, the Expansion Tank is a known source of mystery leaks.

Pinholes or small cracks can occur which only open when the system is hot. The leaking coolant usually drops onto the exhaust manifold and is vapourised so there no trace when the engine is cold!

Graham

 

Several of the nation chains of auto parts stores will 'loan' you a system pressure test kit. Pump it up to 20 psi while cold and the leak should be evident. My tank had a pin hole leak that sprayed a 'fog' of coolant that simply blew away with no evidence of a leak other than vanishing coolant and smell.

 

Much appreciated, gentlemen. I checked the coolant tank and the dipstick this morning when it was cold and there are no signs of any mixing- I'm almost positive the head gasket is OK. Doing a pressure test is a good idea and I'll see about borrowing/renting a device this weekend. I noticed on startup when cold (yesterday), there's a bit of exhaust smoke from the exhaust manifold right under the expansion tank that emits for just a few minutes until it warms up, so that could be a tell-tale sign that the leak is my reservoir. Might also explain why the level doesn't run dry, just down to half (at the seam perhaps?). Though it's hot after shutoff of course, and any excess would probably still be burned off, so maybe this is a separate (and better!) manifold leak. My old 944 Turbo did the same for a few minutes when cold. I should note with the new hoses it got in the last couple years, the 'spider hose' was noted to have been replaced as well. Is this the same?

I actually just bought both RealGauges during the recent sale, but haven't installed them yet! They're on my autumn to-do list...

I'm not driving it until I can successfully ID and fix this.

 

I hope it turns out to be something simple. I think you're on the right track. Let us know what you find out.

 

Could A/C dye be added to the coolant in order to use the UV feature to trace the leak?

 

I'll bet it's that damn octopus hose!! I changed everything I could find, and same issue. We couldn't find any evidence of a leak!! Finally realized it was the one way connector gone bad on the octopus hose under the throttle body. It leaked down but burned off before we could find any evidence. Once we replaced the hose, problem solved!!
BUT, you can't change the one way valve alone. It's the entire monstrosity of a hose set up!!
Good luck! I spent many a night, and many bottles of wine, searching with lights to find that damn leak!!

 

Well after no luck being able to successfully pressure test it even after pinching off all the lines around the reservoir and trying a dozen pumps on each (glad I'm getting my money back on that system- loaner), I think I found the source.

The drainage is dripping from the dead center of the car, closer to the front of the engine, and I'm seeing active seepage from the 1" hose coming off the bottom of what I believe is the thermostat housing. My radiator and other hoses look fine and no bulges, but there's a small coolant puddle underneath that thermostat assembly on top of the engine in a crevase.

See the screw-on hose clamp in the center of the picture? You can probably even see the tiny pinprick reflection of the seepage from the bottom of the clamp, not at the top of the hose, so I think (even though this was apparently already replaced) the rubber needs to be replaced. It's not even quite on all the way up, adding to the evidence. The bad part is... where does this go? I goes under the supercharger nose and out of sight... how difficult is this going to be to replace and what is it called? Is there a diagram someone can provide? I don't see this assembly under reference at JagRepair.com, at least for a XKR.

Also of note, I found the radiator fan assembly totally ajar! It was hanging loose an inch from the radiator right in front of the belts. I wonder if this 'inefficiency' caused this hose to start leaking as it may have been the weakest link and started to go first. I dropped the fans (working fine) back on top of the radiator where it apparently just hooks on top-center (no bolt holes I could see on the sides) and appeared firm. If you work in this area, WEAR GLOVES! The shroud is fiberglass (think about it) and I'm now nursing several micro wounds. EDIT: just checked a similar write-up on JagRepair.com, there are two bolts, one on each side at the top, that I will address now.

This is standing over the passenger side of the car with the supercharger on the left, front of the car on the right.

 

I just re-read this as well. Please tell me more about the dreaded hoses under the supercharger, as that's what it seems to be... I'm actually staying positive about this because the head gasket isn't blown and the car runs great otherwise! I now feel terrible for taking it on another hot and fast run this evening to see if I could make the leak more evident... no more of those until this is done.

 

It looks like the heater feed hose. I am pretty sure the supercharger has to come out to get access to replace it.

 

I started searching for the heater feed hose and found maxwdg's great write-up from a year ago now on the SC removal. It appears the hose in question is clearly there in his photos, in the belly of the beast unfortunately, but perhaps I can get away with not removing both air charging assemblies to get at it (and while I'm at it, the return line as well and the pipe connector he recommended replacing as well- I've got the PNs from him in that thread).

https://www.jaguarforums.com/forum/x...removal-78486/

Am I on the right track? I'm going to have to triple check all this before it gets underway- if this is what needs to be done, it's going to wait until next month for cooler temps. Looks entirely doable for me, just time consuming. I also sent a PM to Gus and he's seeing if he may have any XKR-related docs on this.

Jag #4, you sure got off easy today on our similar issue with your upper radiator hose!!

"It's all just nuts and bolts... It's all just nuts and bolts... It's all just nuts and bolts..."

 

I'm not out of the woods yet, but I'll keep my fingers crossed for your adventure.

 

Thanks- I ordered the two hoses and fitting today. Might tackle this over the holiday weekend.

 

Thanks for your complements on my write up last year. Taking that S/C off is a crazy pain in the a$$ - and it will cause your back to ache, from all the time it it will take. I thought I'd mention that you CAN (just barely) get to that hose clamp that secures the hose that you think may be the leak without taking the S/C off.

You could pull the water pump manifold off allowing ability to pull that hose out from under the S/C just a bit... Undo the clamp and pull the hose off the manifold. Inspect the hose. If it looks OK, redo the clamp and if you are lucky it MIGHT cure the leak - before you have to take the entire top of the engine off.

 

Thanks, maxwdg- for the PM as well. I indeed can get to that screw on the hose clamp, and tightened it up for good measure. After running it to warm in my garage again, the pinprick leak at the clamp was half the size, but still there with tiny bubblage. However, I decided to stick the trouble light under the car, and lo and behold, one drop of orange coolant per second coming off the driver's side exhaust pipe! I tried to trace it but didn't see anything around the firewall, though after shining it between the supercharger and driver's side cooler charger assembly, I can see a small river of coolant way down there. Not flowing, but certainly there and wiggling with the engine vibration. This is just forward of the throttle body- down in there. I'm thinking my pinprick leak at the hose clamp is a decoy- the other end of that hose or the return line has a far bigger leak to get a drop per second going at the ground...

I've got a long 4-day weekend coming up, the wife and kids are going to be out of town visiting some of her family, and I think I'm going to brave the heat and just knock this out over a day or two. With plenty of lager.