Leaking alumimum thermostat housing
 

It leaks from the top cap thing, where the hex socket goes. I need to buy a hex socket for mine, as the sockets I have are too small. I can loosen it by hand, so I would assume it's not tight enough. I have it as tight as I can get it by hand. Or would I need to buy new a piece? Even with me tightening it by hand, it still leaks. Very slow leak, but still.

I'd get my hands on a hex socket for proper tightening.

You mean on the V8 plate (supercharger coolant fill port)? Do you have an XJR? If you have an XJR and it is leaking from that port, an easy way to get that tight without having to buy hex drivers is to take a longer 19mm lugnut, and a 19mm box end wrench, and combine them to use on that port. Think it's supposed to be fairly tight, finger tight won't cut it for holding 15psi in.

edit: reread and saw I misunderstood, guess the NA cars have a port on the tstat housing the XJR's don't.

For the N/A car, I've dealt with a lot of those aluminum thermostat housings and replace them with just a plastic OEM cap. I think it should be molded closed and have a bleeder screw on the top instead.

I agree, doesn't make sense for it to open the way it is, should be closed. Thanks guys, I'll get some hex sockets and see how it goes once I tighten it. If not, I'll put the plastic cap on. Also, my 02 XJ8 Sport has green coolant in it. Should I be worried about that, or just keep using green coolant?

I was a little disappointed in the casting quality on the aftermarket aluminum housing. You have to really torque it down to stop it from leaking, which is not easy as the threads are kind rough like the rest of the casting. It looked like it would pretty well slice into the o-ring too. If you ever unscrew it, it will need a new o-ring for sure. But definitely get the right tool to tighten it.

I bought mine from Welsh Ent. Very good finish and I had the cap off many times with no leaks. But that was five years ago and I don't know if the quality is still high.

+1.
From my forum observations over the years, there seems there are 2 versions, with the version sold by Welsh and some others as the superior quality.

No problems with leaking on mine, but yes, used a hex socket to close it a tat tighter than by hand.

Is the o ring sold separately? Hate to keep asking, but do I need to worry about my car having green coolant? Because by the coolant tank, it says to use orange coolant.

That's a can of worms, I'll leave to the more spirited members here. I will say that both of mine have/had been 100% green, but mind you I made sure they were completely flushed & it was all green, not a mixture & have had no issues as of yet.

Edit :

Do a search on "orange coolant" or "recommended coolant" & you'll see the debates , there are a few in-depth threads here.

https://www.jaguarforums.com/forum/s...archid=6586692



Godspeed

It was actually very loose. I'll keep you all updated as to whether it leaks or not.

I would flush the system and use the orange.

Turns out whilest replacing my tower w/ the Welsh unit I discovered I had a mixture orange/green seems the majority in the system was orange but it had been topped off in reservoir w/ green.

Flushed & all orange now, I feel accomplished lol.

I would but the PO had it all flushed it out when the heater wasn't working, few years ago. What I drained from the radiator was all green.

I don't see the problem....as for closing it right off that is patently ridiculous.
It's a good design, you need to understand how it works.
What i did ws to make sure the top of the housing was completely flat and transfer the flat rubber washer from the old plastic cap.....some of them come with an 'O' ring which doesn't work as well.
Tighten it well by hand and use the correct fitting Allen key and tighten
a 1/4 turn more.
I have had mine fitted for six years and never experienced a problem.