So I have been happily driving the cat without much issues, but now she is back with some little coolant leak.
Today I had time to check, and once warmed up, coolant is leaking from what seems the small connector on top of the plastic thermostat housing (not the hose attached to it).

I am quite familiar with the fragile plastics, and I don't want to break anything, as the car is scheduled for 1/2 year inspection next week.

So, does anyone know if that "cap" can be lifted / removed, how it can be removed, and if there is a cause for leaking there (O-ring??).
Or am I hunting in the wrong direction?

Thanks a lot!
Eric

 

The entire plastic assembly needs to be replaced - the plastic warps and cracks over time. If yours is the factory original, you are fortunate it lasted this long. On the 4.2 XK8 models, it is called the Coolant Outlet Duct, part no. AJ89486. It is an easier job if you also remove the Front Manifold Plate at the top of the engine to get at the two rear Torx T-30 bolts on the Coolant Outlet Duct. If you remove the manifold plate, be sure to install a new Manifold Front Seal, part no. AJ87991. I did this job on my wife's 2006 XK8 back in late November 2014. I believe the thread I posted to document the job was entitled "Slight Coolant Loss...."

 

Replace it with the aluminium thermostat housing. The plastic housings are complete crap like they are on every car.

 

To my knowledge there are still no aftermarket aluminum thermostat housing kits available for the 4.2 engines, only the 4.0 engines....

 

Thanks for the quick advices, along the lines expected.

After a night cool-down, I had the chance to clean up all old crap from hose and plastics.
Then warmed up the car, and could see it start seeping from the hose, not the fitting.

So, short term, I will replace the old hose and fittings, hopefully without breaking anything, and get her through the inspection.

Then I will see what to do with the plastics (I replaced the thermostat tower on my 4L XJ as a precaution long time ago, but I have never seen such for the 4.2L).

 

they last like 10+ years lol