Try looking at the coolant cross pipe, where it bolts to the front of the head. I had one leaking from the seal on one end: the coolant didn't go down the front, it went back into the valley and along the seam where the head meets the block. Almost looked like an external head gasket leak, but it was from the cross pipe seal..

 

Tom,
See if you can get your hands on an inspection camera. It will help you take the guess work out of trying to find the problem. You can fish it into small and hard to get to places and it has a light. Not sure if you can get a loaner from auto parts places. I purchased mine and it was a great investment. Would like to know what you find.

 

JTO is referring to a post I make on another forum regarding a coolant leak that has gotten progressively worst over the past month. As many of these type problems, it only occurred when the system was hot, under pressure and it is impossible to get a hand into the wiring/hose mess at the back of the engine.

At first I thought it was from the Norma connector which is famous for leaking or the hose that runs down the valley under the intake manifold. There certainly had been a leak there over time but using the cooling system test equipment obtained from the local AP store I could not make it leak now.

The leak was in the overflow tank, a little 1/4 inch crack in the side of the plastic, not in any seam and with no sign of any external damage. It obviously leaked under pressure and stopped after it cooled off and the pressure was down. It was in an area that you could never explore while the engine was hot and was not visible without moving the tank.

Guess I will have to find some of Billy Mays' magic epoxy sealant.

The following pictures display the leak evidence under the Norma connector, the leak in the overflow reservoir, the test setup and the pressure test kit. The kit was great, it had 18 fittings to attach to almost any car on the planet. It also had 3 universal fittings, one of which fit the Jaguar. You buy the kit ($180), keep it for up to 45 days and take it back for a full refund. What a deal for a hobby mechanic!

 

That's hilarious, I have an old piece of crap pressure tester, and I made a suitable adapter by screwing a hose nipple into an old coolant blanking cap to fit to the thermostat tower. That'll be $1.50, please. Posted on Roadrash about two years ago, went right past everybody.

Sorry for trying to help, I'll mind my own business. Don't suppose you'll be wanting to buy a good used expansion tank, either.

All the DIY guys point to the heater hoses beneath the intake when they see a coolant leak anywhere in the neighborhood. That's a false assumption 99% of the time. Since you weren't getting any better advice and there was no evidence of a resolution, my enthusiasm got the best of me. I'll remember to keep it in check.