Borrow a cooling system pressure testing kit from one of the big-box auto parts stores such as Advance Auto Parts or Autozone. You put down a deposit on your credit card, take the kit home, use it to find the source of your leak, then return it for a full deposit refund on your card. This is what I did when I could not find the source of a tiny coolant leak in my wife's 2006 XK8 back in November 2014. Pressurizing the cooling system using that kit revealed the source of that leak in seconds, and I could then proceed with obtaining the necessary parts to fix it....

 

Tom, you must have deep pockets brother. I wouldn't throw money (big money) on a radiator without being 100% positive that is the problem, let alone $75.00ish on a DVVC.

Jon gave you the best advice, "rent" a coolant pressure tester.

 

I guess that is an answer. Did you simply remove the cap on the reservoir and pressure from there?

I am curious- where was your leak?

Tom

 

Yes, you pressurize the system through the coolant expansion reservoir after removing its cap. You use the small hand pump that comes with the kit. The kit you borrow must also have the appropriate adapter that looks like a pointed empty ice cream cone that fits snugly down into the reservoir's opening....

My wife's XK8's leak was in a very typical spot for the 4.2 engine - the coolant outlet duct that also houses the thermostat. They are made of plastic and like so many plastic parts in our Jaguar engine bays, they tend to warp and eventually leak as the years go by due to being baked by the engine heat. This is a very different engine and system from the 3.0, though....

 

I have not yet replaced anything, but based on several tests (and no I have not yet done a pressure test and think I do not need to do one now).

I have monitored my folded paper towels on the DCCV and even though I might have used it I choose to leave the Climate Control at low and not use any heat at all and guess what- no leak.

When one day I was cleaning the car and engine and let it run- it definitely with the heat on could be heard opening and closing and on that one day, my paper towel showed some dampness and an orange spot. So apparently when I use the heat at all, the side toward the heater core on the valve and apparently past the valve stops, I get a very minimum seepage and I assume that the location is toward the radiator and between the seal where the metal and plastic come together.

I never use Auto on the CCM nor do I have anyone that rides with me that adjusts their side differently than mine,

So I am going to replace the dccv and the heater hoses and while I am about it will replace the lower radiator hose, coolant reservoir tank and the hose from the tank to the upper radiator hose assembly.

It does appear that the best approach is from the top and in that regard several questions.

1. How do you easily get off the lower hose on the dccv or once the bolt, electrical connection and heater hoses are loose- is it simple to get to the pressure points on the clip which point downward. It is such a PITA to deal with the radiator splash shield and the undercarriage.

2. When replenishing with new coolant, where are the bleed points on the 3.0 (beyond the one on the coolant res. tank) or should I just run the heater at high and then let the system work itself out and pay attention to the coolant levels and fill as needed.

Appreciate your help and thoughts. And I think one of the users said it should be part of monthly maintenance to wipe under the DCCV to see if any coolant is there- to prevent the problems that get caused by the piece of junk DCCV.


Thanks

Tom in Dallas/Plano
3.0 2005- 101,500

 

I finally started too get a leaky water pump at 105 K, so I decided (I already had the parts) to replace the water pump, lower radiator hoses, the DCCV - the 2 heater hoses that came off of it, the coolant tank and the hose from the tank to the turret on the upper radiator hose.

Once off, it was the DCCV that was leaking out of that metal to plastic seam, but after the valves were closed. So no leak with AC on- small oozing leak when heater on.

No leak now.

Tom in Dallas/Plano 05 S-type 3.0 105K

 

Thanks for posting your successful results...i have been following this thread with a similar problem..mine turned out to be the radiator tank seam close to the dccv valve...the insulation foam was soaking up the small amount of coolant...finally the seam gave way and i replaced the radiator...i was getting ready to replace the dccv even though it was only 18 months old...the pressure check would not reveal the leak...it would lose pressure down to 9 lbs then stop...hard to see that particulr spot...all is well now