In a previous thread I got advice about a puddle of oil under the car that had never been there before. The local Jag dealer told me they didn't work on the older cars. I took it to a shop advertising experienced factory trained Jaguar mechanics. They told me the rear main seal had blown out and the valve cover gaskets were leaking which was pretty much what everyone told me. After racking up a $1,400 bill for the seal and gaskets they told me my rough idle meant I probably needed new spark plugs. I didn't know what they were talking about since this engine and transmission have always been silk. I told them not to change the plugs for an additional $350. As I backed the car out of the parking space at the garage the engine ran terrible and I had no brakes. I had to stand on the brake pedal to stop the car. I immediately went back in and spoke with the mechanic. He said the brake vacuum line was in the vicinity of the valve covers and maybe came off. I have to doubt it worked when someone drove it out of the garage to the parking spot and then fell off if that indeed is the problem. He also said the leaking valve cover gasket filled the spark plug recesses with oil and that may have shorted out a coil causing the roughness. I have seen the oil around the plug before chasing a fault code, but it never caused a problem with the engine running, I cleaned the oil and everything was good. He said pulling off the plug boot with the oil around caused an issue. He also said it may clear itself up after driving the car for awhile. I told them I wasn't driving the car with no brakes and left it there. Sorry for the long story. Is there a possibility oil in the sparkplug recesses all of a sudden caused a problem when it had been running fine up til now? He sent me a picture of the rear main seal loose in the engine, but said he couldn't find anything that would have caused it. Hoses weren't pinched, the PCV valve was good, and they didn't find any pressure when the oil cap was removed. Could this have been working it's way out then finally just popped out (coincidentally the day after I let my son drive the car for the first time). I don't have a lot of faith in the mechanics at the moment and need your thoughts and experience.

 

It's not uncommon for the 4.0 litre unit to develop an oil leak around the cam covers and spark plug boss seals. Even with a coil unit shorted, you may not have the MIL come on, but having a misfire causing raw fuel enter the exhaust is not good for the catalyst on that bank.

With a bit of patience, you can replace the cam cover gaskets, spark plugs and spark plug boss seals yourself. With the cam covers removed, it's also a good idea to inspect the secondary timing chains and tensioners.

 

I just got a call from the shop saying they found a nicked vacuum line by the catalytic converter heat shield. They fixed the vacuum leak and now the brakes work and the engine runs fine. They are going to deliver the car to me, which is nice, so hopefully the car will run as good as it always has but without the oil drips and recent puddles.