Looks like there is something else I need to order so I can address it during my leave next month- this sensor at the left-front corner of the engine, middle of the photo, is weeping oil. Can anyone tell me what it is please, even better, how it seals- e.g. o-ring etc?

 

A detailed search of the workshop manual reveals this is the Oil Control Solenoid for the Variable Cam Timing, It appears that the seal can only be replaced by removing the valve cover.. If anyone can confirm or deny, I'd appreciate it.

 

On the 4.0 liter in my XK8 I did not remove the valve cover, although it is recommended by the service manual. I replaced mine by disconnecting the electric connector on top and sliding the new ring down into place. This after removing the old O-ring and cleaning the area of course. No further leaks for over 8 months.

 

It is just the seal around the VVT sensor, part AJ82856, removing the valve cover is not necessary.

 

Thanks to both replies, very much appreciated- especially the part number. I'll order two of them and have at it.

 

Hi not sure if this was answered or not, but the seal itself pulls off

I myself am wondering if these are leaking, will it cause a vacuum leak ? I’ve recently just replaced the brake booster seal from the throttle body manifold as had a high leak, but now I’m getting lean codes after a long journey but no cel lights anymore

 

No vacuum, it's in the valve cover so communicates with the crankcase rather than induction system, just weeps a little engine oil.

 

I replaced this on mine a few weeks ago, its fitted from the outside so you don't need to remove the valve cover. Its on quite tight, you just need to jab it with something like this to pull it off:

To fit the new one just slide it over the VVT sensor and push down firmly.

Despite what it says in the workshop manual removing this seal before taking the valve cover off makes removing the valve cover much easier as it gives you more wiggle room to get it clear of the VVT sensor, i.e. you can change the VVT sensor seal without taking the valve cover off. I suspect they say to remove the valve cover to make you change the valve cover gasket and o-rings as they are probably coming to their end of life too.

I replaced a leaking VVT seal on one bank last year, then 6 months later had to replace the valve cover gasket and spark plug o-rings because they started leaking, which meant replacing the VVT seal again. In the last year I've replaced both valve cover seals and the o-rings due to leaks, it was actually relatively straight forward to do.

You might want to check the PCV system is working properly, you might have excessive pressure in the crank case that isn't being relieved properly so its forcing its way out via the VVT sensor seal, if you plug that leak its going to try and find somewhere else to get out. A typical thing on this engine is that the PCV hose back to the throttle body gets brittle over time and creates a vacuum leak, preventing the PCV from operating properly. Run your hand or a cloth along the PCV hose and see if there is any oil on it, if so its probably leaking and needs replacing.