2006 XK8....

I typically keep the coolant level in the expansion tank at a quarter-inch or so below the bottom of the filler neck. In the last couple of weeks the coolant level has gradually dropped by a total of about three-eighths of an inch (I've been checking it every morning for the past week). I topped it up yesterday. No visible leaks, no coolant smell, no orange stains anywhere I can see with the engine dust cover removed. The service history of this car does not show an expansion tank replacement so I assume the tank is original. The car was built in May 2005....

I know the initial suspect in this case is always a hairline crack or a pinhole leak in one of the tank's black plastic hose nozzles with the escaping coolant evaporating in the hot engine bay before it leaves a stain somewhere. But some owners have also discovered that their tanks have sprung a pinhole leak from the tank seam....

Any tips on exactly where to look and how to go about nailing down the culprit from those of you who've already dealt with this issue? I don't mind ordering and installing a new tank but I want to make certain that I don't waste my money if the existing tank is not the issue....

 

A pressure tester and a quiet, bright garage where you can hear/see where the coolant is coming out from with the engine off is the best way to find it.

 

Will a pressure tester always generate enough "oomph" to force coolant through even the tiniest of pinhole leaks to the point where the leak can be seen/heard?

 

It will generate more pressure than the system does on it's own. I used my tester on a XKR with a leak that I couldn't see yesterday, and at 15 psi it threw a stream out of the outlet hose.

 

A tester rented from you friendly, neighborhood auto parts store is capable of applying twice or more the pressure that the system normally operates at. Pump it up to 20psi and any leak will be plainly visible.

 

Jon, The tester normally goes up to 14 PSI and this will generally be enough to hear and see a leak. The hard part is finding someone with the adaptor for the expansion tank. I have the tester but not the needed adaptor, plus a long way to come. I do have to get one, as surely mine will do it sooner or later. Autozone my have one. It's just hard to hear in a busy place as XKR pointed out. Keep an eye on it as I know you will. Jan does know to stop if she starts to smell antifreeze


Wayne

 

Hey Wayne,

I made Jan smell my jug of Jaguar coolant last Saturday so she would be able to recognize the scent if necessary. She wasn't very happy about that as you can imagine. Her next solo trip to visit her mother in Tampa will probably be the week before Christmas so I need to figure this out before then. I'll check with the local Autozone and Advance Auto Parts to see if they have the necessary pressure tester/adapter. If not, perhaps one of the local indies that I trust can run this test for me....

 

The only one that will work in the big box of 20 or so is the universal one shaped like a pointy ice cream cone. Wiggle it down into the reservoir as far as it will go and apply the expansion lever. That seals it just fine.

 

The local Autozone does indeed have a loaner pressure tester/adapter kit for a $75 deposit which will be fully refunded to me when I return the kit to the store. I'll give this a shot within the next few days and see what it shows, and I'll update this thread with any results. Thanks once again to our experts here for your very valuable advice....

 

You can buy a leak detector for coolant. Add it, run to operating temperature and any leak will be visible with the special glasses in the kit. Most auto supply stores sell them and typically they have the ability to detect different kinds of leaks: oil, coolant, etc.

 

Update:

The pressure test kit loaned from Advance Auto Parts this morning quickly revealed a leak in the car's thermostat housing. The housing assembly looks to be held together by three bolts and the leak is coming from the bottom seam where the thermostat cover bolts into the thermostat housing. So is this simply a failed gasket inside the thermostat housing assembly that needs to be replaced, or does the entire thermostat housing assembly need to be replaced due to the age and heat cycles of the car?

This car has the 4.2 engine. I remember reading about "thermostat tower" plastic failures in the 4.0 engine, but not so much for the 4.2 engine. Like I said, this leak appears to be coming from a seam, not from a piece of cracked plastic....

 

G'morning, Jon

I did this job on my '03 recently. There is a kit consisting of a new thermostat, cover, and seal that should work for you. The seal looks like a big 0-ring from a distance but has a more complicated cross-section.

Pretty easy. A bit of coolant loss of course.

 

Dennis,

Many thanks for your quick reply. Where did you source your repair kit? Can you provide part numbers as well? Thanks....

 

Jon,

Nothing in my file on this. Which is strange. It's possible I got the kit from my indie. I'm drawing a blank. SNG Barratt will surely know of it.

One strange aspect to this kit. You have to assemble the thermostat. Maybe this is not so uncommon, but I've never encountered it before. Use the old one as a model; otherwise it's possible to get it wrong.

 

Jon, Glad you found it so quickly. You may be able to use the drain system I did on a tower replacement. Saved the fluid and the environment. If interested, I go find the write up. I don't know if the 4.2 has the intake manifold interference on the rear bolts, if so, I will mail you the crow foot tool I made.


Wayne

 

Dennis,

Thanks for your additional information. I'm surprised you have no documentation regarding this kit. I keep records of everything and assume all other DIY guys do as well. I guess this one fell through the cracks....

I'll call SNG Barratt tomorrow morning. Hopefully they'll know exactly what you're talking about....

Do you recall any specific tools or tips that were needed to successfully effect this repair?

And is there anyone else here on the forum who is familiar with this kit?

Thanks in advance for all responses. I believe that using the pressure testing kit this morning to locate this leak further opened up the leaking seam. It's a fairly steady drip-drip-drip-drip now from the thermostat housing with the engine running. So my wife's XK8 is officially parked until I can source the kit and effect repairs. She's already pestering me about not having her preferred car available....

 

Wayne,

Many thanks for your kind offer to allow me to use your custom-made crow-foot tool. I have no idea if our 4.2 has the same bolt access problem that your 4.0 does, but it would be great to have that tool in hand just in case....

And yes, please post the write-up of the drain system you used to conserve your coolant....

Thanks!

 

https://www.jaguarforums.com/forum/x...ousing-119815/


Jon, I found it and I will pay attention on the bolts, when someone lets you know.
It's about Item 7 or something like that.
Wayne

 

Thanks Wayne. I'll study the write-up very carefully. I was just outside again and was able to get my 8mm socket pretty easily on all three thermostat housing bolts that I could see, but they all face frontwards. Not sure where the troublesome rear bolts that you mentioned would be. Maybe I just missed them, or maybe they don't apply to the 4.2 engine....

 

Gents,


Apples and oranges here. Old style thermo housing vs. '03+
No bolt access problems for Jon's job.
(edit: hadn't seen cjd777's post. This from the department of redundancy department.)