I have a coolant leak but no visible coolant anywhere. I would fill it up drive about 1/2 hr and low coolant light comes on. I pressure tested and hear a gurling sound on the passenger side center or towards the back but cant tell the exact location. Its only air but no coolant. The system will not pressurize at all. I keep pumping the tester but will not come off 0 pressure. Engine oil is clean and not over filled. No bubbles in the coolant reservoir when engine is running. Anybody with a clue?
Its a 1997 XK8 convertible.

 

Tried running the engine to get it hot and the water started to overflow from the reservoir. I do thing i see some bubbles but very few. Still no water in the oil and no weird exhaust smoke.

 

Is the remote header tank filled to the brim? If it is not and the header tank cap is not sealing properly then you will lose air pressure but not coolant either past the cap to atmosphere or, more likely, down the small hose to the expansion tank which is behind the righthand side wheel arch line. Listen with your head inside the wheel arch and you might hear the air escaping.
The cure would be a new, or silicone greased pressure cap and to check that the expansion tank is about half full of coolant,

Richard

 

I hear air escaping but from the opposite side of the reservoir. the passenger side. (left side drive car) its like gurgling sound. like when you blow into a glass of water with a straw. Between the valve cover and firewall. Just hard to tell. I'm assuming its not the cap because I'm using a different cap to pressure test. Thanks

 

Near the firewall on the passenger side of of lefthand drive car does sound as if it could well be from the expansion tank which is attached to the firewall, or from the pipework which goes across the firewall from the header tank down to the expansion tank.

Are you using the special cap required to stop air leakage down to the expansion tank? If the cap you are using is a simple cap which seals against the top flat lip of the header tank, then it will never work and pressure will immediately bleed away. The Jaguar system is more complicated than a simple combined header tank and expansion tank.

Richard

 

The header tank is the one on the drivers side with the 3 tubs coming out. Where exactly is the expansion tank located. Thanks in advance.

 

ON LHD cars, passenger side front wheel well. If RHD, the driver's side front wheel well.

 

The ATMOSPHERIC CATCHMENT TANK needs to be blocked off when performing the pressure test!!!!!!!!!!!!!!!!!

 

Please advise in how to do that.

 

plug the line coming out of the expansion / header tank that goes to the recovery tank

Z

 

I did explain this in my post #3.

The two tanks are referred to by various names but I call the black one which is in the engine bay the "remote header tank". I call the one which is hidden behind the wheel arch liner the "expansion tank". This second tank is open to the atmosphere, which is why you can hear the air escaping, so is often referred to as an "atmospheric expansion tank", or similar.

Richard

 

I just use the terminology that SNG Barratt does in their parts catalog. If they don’t know then who does, out side of the manufacturer.

Z

 

Attached to inner wing/firewall on LHS = "Coolant reservoir"

Under front wheel arch = "Atmospheric recovery bottle"

...says JEPC / SNG Barratt.


Of course, I've never got them mixed up...

 

Even Jaguar do not use consistent names for the two tanks between their different models. 😉

In such situations, I prefer to use my own descriptors based on cold, hard, experiential logic. Nearly all radiators have a header tank and the Jaguar one is remote, and nearly all coolant systems have a tank for dealing with the expansion due to the rise in temperature and the Jaguar one is in the wheel arch. 👍

Richard

 

That may be so, but the above terminology is what Jaguar has chosen for our X10n series cars, and is relevant here.

"I love standards: there are just so many to choose from"

 

 

Thank you for that advise. I blocked off the overflow and found the leak. Its under the unit in the picture. It looks like some kind of water distribution unit.

In the middle of the unit in the rusted area its spraying water.

 

Took it apart and it looks like the thermostat housing gasket went bad.

 

With the atmospheric expansion tank being open to atmosphere, how does the system maintain pressure in normal operation?

 

As I explained above, it's not a simple cap on the remote header tank. It's a double action cap which seals at the top but has a spring-loaded central section which allows pressure out into the expansion tank when it builds up. It has a one-way action and as the system cools down it allows coolant to flow back into the header tank which is why the header tank should always appear full to the bottom of the neck.

Richard