Should there be a sealing ring or something where the low coolant sensor goes into the expansion tank? I have a leak there and the tank was replaced only three years ago. I can see a leak where the black electric connector goes to white plastic and then goes into the clear plastic of the tank and it seems loose. Or is this just another expansion tank failure? Its a 2004 2.5 v6 petrol.

 

When I replaced ours "last year" a month or so ago, there was a blue tiny O-ring between the resevoir and the low coolant sensor.

 

Thanks Rick. I have taken the expansion tank off and tested it in a sink like a bike tyre by pumping air in and can find no leak. Maybe it needs to be hot and at higher pressure to leak. There is a tube over the low coolant detector wich doesnt leak so maybe the coolant is dribbling down. I am reluctant to go off and buy a new tank when I cannot find a leak and the previous owner had a new one two years ago but I may have to.

 

I am now wondering if the cap on the expansion tank could be the fault. It is hard to do up tight as it starts clicking too easily. The cap is made by fomoco in india, is this right? Sometimes there is residual pressure in the tank even when it has fully cooled down and this morning it bubbled coolant out even though cold ,but I may have overfilled it. I think this mystery will run and run.

 

Three actual years in S-Type years is 150 years...It's probably leaking, I think Jag was going for Guinness book of world records for the most poorly designed tank...

 

I concur. The coolant expansion tank in our 2005 S-Type was replaced with a new one in September 2009, but I continue to check it every weekend as part of my routine inspection process. Gotta check the expansion tank and the DCCV regularly, and it only requires an additional 30 seconds to do so. Time well spent once you understand the risks of not doing so....

 

Thanks for that, the new cap was much stiffer at first so I could do it up tighter. But the next day it clicked sooner so I couldnt get it so tight. The cap seems as cheap as the tank, the words on the plastic suggest its made by Ford in India. What idiots to put such poor parts on such an excellent car.
Still watching for leaks its my new hobby.

 

There's little (nothing?) about the cap being a common problem.

They click to prevent overtightening, don't they?

Each cap includes a pressure relief valve IIRC. No signs of them being triggered commonly.

Probably because the leak occurs elsewhere

 

Thanks for that Jagv8, I am still trying to get the air out as I can hear bubbles gurgling around, is the metal pipe high up on the Uk passenger side part of the cooling system? It seems to have a valve on it but I do not want to let out aircon fluid by mistake.

 

That'll be the aircon high side pipe. Thanks for the pic Rick!

 

You could safely undo & remove that black cap if you wish. There's a valve tucked away below it, which the a/c matching part releases. The cap just keeps it clean, as any dirt in the a/c is very bad news and some could be allowed in when the hoses are attached, if that inner part wasn't clean. If you do have a look, put the cap on afterwards.