Today was unusually warm for January and Trenton and I were able to do a bit of maintenance on the Jag. It had trouble starting and running well last night on the way home from work. So, I thought I would swap out the distributor cap and spark plug wires form the parts car. If you’ve ever priced parts for a Jaguar, you will know why I didn’t just purchase new parts. Not only are they three times as expensive but they all have to be special ordered. The parts car was a good idea.
Over the past few weeks, I have noticed a bit of oil on top of the valve cover gasket. But try as I might, I could never pinpoint where the leak was coming from. Today, I saw it again and noticed that the oil was spraying onto the underside of the hood from above spark plug #5. Hmm… There were no leaky hoses nearby and the only oil caked pieces were at the front of the engine. I couldn’t figure it out, so I decided to just swap out the distributor cap and wires and see if the car ran any better. All but spark plug wire #2 from the parts car came off easily. The surprise came when I began removing the wires from the daily driver.
Each spark plug is located in a 6-8″ shaft in the DOHC head. When I pulled the wire from cylinder #5, the entire shaft was filled with oil. It was the same thing for spark plugs 2-5.
“Houston … I think we have a problem.”
My immediate reaction was to think that the head was cracked and leaking. But I later found that the valve cover was not bolted down tightly. After removing the valve cover, I checked the gasket and it seemed to be good enough. It was just the bolts (Phillips head!) that were not tightened down. At least that’s what I hope it is. After cleaning out each spark plug shaft, the top of the head, and the inside of the valve cover, I reinstalled the valve cover and it seems to be good to go.
That afternoon, I confirmed with a Jaguar mechanic at Motor Werks in Painesville that these valve cover gaskets do get old and brittle over time. So, it’s probably time to replace it. But before I order one, I’m going to see if torquing down the bolts will solve the problem. I’m also cautiously hopeful that this is the reason white stuff was in the oil. Perhaps it was just moisture getting into the oil through the loose gasket? As always, we shall see. There is never a dull moment in my driveway.
1 thought on “1990 Jaguar Sovereign : Leaky Valve Cover”
“Undid them.” Nice grasp of the English language, Andy.
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