Ok, so... this is where my slow leak is coming from. Is there a rubber washer in there?? If so, is it easilly changed? This is a 97.

Thanks

 

I would be somewhat alarmed at the color of the dried material as well as the leak itself. If it were mine, I would replace the cap and change the coolant, replacing the leaking clamp on the upper hose in the picture. The whitish material looks like some mineral deposits that should not be there. This happens when phosphates are present, you don't want these in there. This picture tells that there is more to worry about than you think. I also suggest replacing the thermostat while you are messing with it if the thermostat has more than 60,000 miles on it.

 

Yes there is an o-ring under that cap. I just replaced mine. It's a standard size. You don't have to buy a Jaguar part.

 

What size? Where should I get it? Local auto part?

 

Please take some info from someone that deals with this for years. Like oldmots said. That white color is a total breakdown of coolant and i guarantee you have that white sludge deposits in areas of the cooling system. Also you have a 97. Any plastic that old is soft and will break when you touch it/work on it. If that were mine, i would chemicaslly flush the system real well. And buy a new crossover pipe and metal thermostat housing and thermostat. It comes complete from many suppliersfor around $85. Thats what jag charges for plastic not complete.

 

The white slugde is no big deal. I have been running only water for the past month, it is to be expected in any car running only water. Rest assured, a complete flush is on the way. Now, about that rubber washer. What size is it? Anybody have a part number for it?

 

Just buy a sheet of rubber gasket material at the auto store and cut it, cause it only comes from jag as the cap and washer together

 

The o-ring is 1/8-218

 

If it were me I would replace the housing and all associated hoses. Do not fix it with a Band-Aid, Brutals comments are dead on. This link will help Thermostat Housing Replacement

 

I saw that page and the one with the aluminum housing. I was thinking about it, but my housing is perfect. No leaks or deformations. My hoses are not as bad as those pictured on that website, that would've scared me if they did. I don't want to start replacing parts that don't need replacing just yet. In the future, I will definitely consider the new housing type for sure. I thing I will order the new cap with the rubber o-ring

 

The choice is yours!