So a little over a year ago and 15K miles, I replaced my spark plug seals, valve cover gasket, and isolators on all 13 valve cover bolts.

Upon removing the valve cover, the isolators were mildly damaged, hard, and the spark plug seals were in worse shape, having allowed a fair amount of oil to drain into the spark plug wells.

Anyway... where do you guys order your spark plug seals and isolators from? The dealer wants around $10 each for everything (over $190), and I can find them for a range of prices online. I just want them to last longer than a year if I haven't got to spend nearly $200.

 

$200 is horribly steep.

You should be able to get the valve cover gasket and plug seals for about $50-60 total. The isolators main job is to prevent galvanic corrosion between the magnesium cover and aluminium cylinder head. So long as they are intact I wouldn't replace them. If you need to you can get them for $4-5 each or less.

Look at Captain's Jaguar or Motorcars Ltd websites.

The main thing is to ensure that the sealing surfaces are clean and level. Also make sure you dig out any sealant that may still be in the valve cover groove. It's quite common for the cover to warp a bit. I always smear a little RTV ultra black on the boss seal faces and also on the inside of the valve cover gasket, paying careful attention to the half moon seals at the back.

Then once in place, ensure you don't over torque the bolts and use the tightening sequencing shown in the service manual. Too tight and the cover will leak.