I am hoping someone can help me with a new issue on my 2006 Jaguar XJ8. I noticed an error message telling me that coolant was low. It was, but only a bit low (i.e. I could still see coolant when I removed the radiator cap). I topped it off and drove with no issues. The next day, there was coolant on the drive way. Removing the radiator cap showed it was low, but still there was a little coolant visible. Topped it off and drove the car again. This time, I drove it for about 30 minutes, checking the dash to see if the red light would come on with a low coolant warning. It never did. So, I took the car home and parked it. I checked it a few hours later and there was coolant on the driveway. Removing the cap showed the same thing ... not a ton of coolant missing ... even so, it was obvious there was a leak. I had to take go to a scheduled appointment, so I topped off the car, drove it, parked, made my meeting (it was only about 15 minutes long) and went back out to the car. There was NO coolant under the car. So, I drove it home. I checked it again a few hours later and this time there was coolant under the car.

My conclusion ... and please keep in mind I am not a mechanic nor do I play one on TV ... the coolant is only leaking after the car cools to a certain amount. I can drive it for a good period of time with apparently no loss of coolant. I can have the car off and as long as the engine is hot enough, there is no loss of coolant. But once the car cools to a certain point (i.e. sits for a certain amount of time), I lose about as much coolant as would be in the reservoir.

I did a spot check of the reservoir and it looks okay. In fact, I'd had to replace it about 4 years ago, so the one in the car is pretty new (it was new when I replaced it). Again, not a mechanic, but could this be a hose that is not fitting tightly somewhere? The fit gets snugger as the engine heats up and then, when it cools down enough, and with there still being some pressure inside, some coolant is forced out?

The leak appears in the very front, almost the middle-front, of the car. That's where the majority of the spillage is under the car and I saw a few drops hanging off the bottom-front of the car. The radiator looks dry ... as much of it as I can see.

Any ideas before I get someone to tear into this thing?

Thanks in advance for any help with this.

 

After a cold soak, preferably overnight, use a cooling system pressure tester to pressurise the system to 1 bar and inspect for leaks.

Typical areas for leaks are around the water outlet, or the EGR return pipes under the inlet manifold.

 

Again, not a mechanic. Sorry for my ignorance, but what is a "cold soak"? And, of course, I don't know where any of those are (ERG return pipes, etc., but will do a search ...).

EDIT - Hah! I read your message wrong! I thought you said, "ADD a cold soak" not AFTER. Sheesh. I need more coffee!!!

 

Well, I'm glad I'm not the only one who misreads some of these postings!

The water outlet is at the front of the engine above the water pump and has hoses that connect to various other parts and the radiator. If you're not sure, have a Jaguar specialist look at the vehicle to correctly diagnose the source of the coolant leak.

 

I haven't worked on an XJ8 and so I'm assuming the crossover pipe is plastic like the LR3 -- assuming this to be the case I would check the plastic crossover pipe at the front of the engine that connects both cylinder heads and also includes the thermostat housing. I believe this pipe also includes the engine coolant temperature sensor. The plastic on these can fail over time (it did on my LR3) and there are various fittings that can leak. I would inspect this part and its connectors. Other areas in the front to check include the water pump housing.

When I address coolant leaks, the approach I have had the most success with is to use a combination of a) inspection, b) pressure tester as the other poster suggested, and c) UV dye. You can start with the first one, then add the pressure tester, and if it is still elusive dye is probably your best bet. Note that if you are still running the original OEM coolant color you might need to find a color-matched dye. If you have green or yellow coolant, the typical green dye will just boost its 'green-ness', in additional of course to being visible under blacklight. You'll need a blacklight and the typically-included yellow glasses.

Ramps also work well here if you have them, if not I would put the front of the car up on jack stands.

Small coolant leaks can be difficult to find sometimes because they might only occur under heating and cooling cycles. In that case the pressure test will come back without any issues, but the dye will remain after driving and identify the problem.

Good luck with it. You should be able to rent a pressure tester from an auto parts store, and the black lights can be picked up cheaply and are good to have (very useful if you have dog that occasionally uses carpet instead of grass!).

 

My 2006 leaked more than a drunken sailor after 5 pints. We replaced the coolant expansion tank, it was all cracked. Six months after and around 200 miles more (I travel a lot, out of country) it started leaking again, I decided to replace all the pipes. Go to a mechanic, one that know these cats.

 

On my V8, an XJR, it was the auxilary water pump that was leaking. Not a huge ammount but enought that after about 5 days the light would come on. It lives to the left of the expansion tank down in the rats nest of pipes.

 

Thanks, everyone! I think I will take my car to someone who knows more than I do on this subject (which is just about anyone!). I do appreciate the replies and help.

 

Just wanted to update this (in case anyone was interested). I was able to witness the leak and it was a hairline crack in the overflow tank. A simple and inexpensive fix.

 

JDog it happened to me 2 months ago on an XK non turbo. The small hose leaving the coolant container heads toward and under the plastic cover over the intake manifold. Remove the plastic cover. At about the 18 inch mark there is a straight plastic connector that deteriorates. Replace it with a metal one. Pooling of coolant takes place there.