Cleaning up the undercarriage which I like to do on occasion on my cars as it is a good chance to check for loose hardware, missing fasteners or any other odd potential problems. In doing so on my XK8 I discovered a fair amount of dirt and tar coated road gravel which makes it stick trapped in and on the rear subframe. I would say enough to fill a cigar box from the sub-frame flanges and upper surface. Took about a half hour to get it off the flanges and out of the nooks and crannies. I would think where you have road salt and slush to deal with this would be a nice source of corrosion, and might warrant some attention to keep cleaned out.

 

I'm on the lookout for a good replacement as they tend to rust from the inside out in the UK.

 

I looked under my girls' skirt

12 years old, a bad thing to do.

 

I just dropped the rear sub-frame of my 2004 XK8 Monday night and got it stripped down last night. It looked almost as good as yours from below but I was suspiscous of all those places I couldn't see. As you say they look like grit traps. I had nothing wrong with the rear end except it is a twelve year old canadian car, and I figured shocks and bushings are probably due. The attached picture will tell the tale. Parts in for blasting this morning, then I will repair that front rail and get it all powder coated. I am going to put a sealant of some kind between the subframe and the vertical triangle shaped piece when it goes back together.

 

Melbec,
Are you aware that repair panels are available in the U.K. for just your problem?
I used one and it fit really well and is lot cheaper than replacing the whole sill.

Jaguar XK8 XKR (X100) Body Repair Panels Rear Half of Sill | Jaguar XK8 and XKR Parts and Accessories

 

I'm partial to just good old fashioned oil spray.

But you might like one of the new seam sealers.

From 3M I think?

 

How very rude!

 

Thanks, I have left the car with repair people but have sent them your link.
Many thanks.

 

And another rusted mess. I bought another a frame from a junk yard.

 

This is by far the best product I have found for internal cavity rust stop and rust proofing. Just be careful to protect any surfaces where you don't want it, it is nearly impossible to remove. I think some strategically drilled holes in the sub-frame would allow access and it would be nice to somehow get a borescope in there first to see what is going on internally.
Eastwood Internal Frame Coating 14oz Aerosol