hello everyone,
in my xj6 4.2 from 1982 with 140,000 km for a week I noticed an oil leak from the small hole under the intake manifold; I then opened the oil filler cap and a breather reports a loss of compression from a piston and therefore, given the normal functioning of the engine, I believe it is a segment of one of the pistons; the car doesn't make any smoke
I intend to redo the engine but the specialized Jaguar vintage mechanic is about 100km away. Can I bring him the car without worries?
I'm worried that the oil vapors could fuel an uncontrollable self-ignition
Thanks for your thoughts on this

 

you can drive it ok but did you do a compression test? how does opening the filler cap & breather report a loss of compression?

 

I agree with Tom.

Any of my XK engi=ned beasts since 1968, that had that hissy fit were generally caused by too gentle driving, too many short stop/start runs.

We were 300miles from anything, so the chances were rare at best, but when one the pops up, change the oil, go for a blast, HARD. Alwats fixed them.

I have refreshed a few of those engines, and damaged pistons or rings, NEVER.
One had some alien marks in the crown of one piston, which I put down to a spark plug tip bouncing around.. It cleaned up well.

I would suggest an oil change, then a good 300km run, and being where you are, PLENTY of places to go. I know fuel is EXPENSIVE, but if one tank of Bang Juice saves an engine rebuild, cheap as.

These engines are good for 500K kms with minimal car, but they MUST be driven as designed.

Good luck.

 

I checked the fume exhaust and the screen is clean
the leak manifests itself with a hiss and a slight pressure both from the oil filler cap and from the vapor exhaust that goes to the intake
I did about 200km not on the motorway but still not at low speed
the oil is castrol classic 20-50 with few kilometers

 

I am assuming this "hiss" is with engine being rotated by hand with the spark plugs installed.

If so, perfectly normal for ANY internal combustoon engine, as the Comp Pressure is bled past the ring gaps on the compression stroke. That is why, when hand turning with plugs insitu, you meet resistance, wait 2 seconds for the bleed off, and rotate some more.
All internal combustion engines "hiss and huff" as part of their normal cycle of life.
All mine did, and do, that exact same thing.

As for driving it to the workshop, go for it, I seriously doubt anything sinister is going to happen.

 

I'm talking about the engine running at idle, the snort and hissing sound is on the oil filler cap which is open with the engine running.
that is, the crankcase is under pressure and this was not the case before
Thank you

 

On front of engine is a metal pipe that goes into a rubber ( well used to be rubber, likely hard cracked plastic by now) fitting and there is a screen behind it, i would check there before I go any further, air gets sucked through it to I believe the air filter housing, can’t remember exactly as my 4.2 is long gone!!! It’s a basic pcv setup if I’m not mistaken ( but I usually am, lol)

 

already checked free from dirt and blows oil vapor which is deposited as I said before in the intake manifold
grazie

 

the motor is always under pressure, that's why there's a breather, opening the filler cap will always give odd noises, if you have the tools, do a compression test, take a photo of the oil leak and post it here - sounds like rocker cover - briciola > looks like you're talking yourself into something that most likely isn't there, ..... do the comp test - post a pic or get someone to do it for you.........then people her can give the best advice........

 

Read it one last time, just to be sure.

At 140K kms in 40 odd years, I reckon its got glazed bores, and savage blow-by, from lack of use.

I know your new, so I am being gentle, trust me.

A re-ring, hone the glaze from the bores, and it should be as good as it was when new.

That XK engine needs to be driven, and as they age people are scared of that, I have never understood why.

That breather is doing as designed, and the accumulated oil in the Inlet manifold is "normal" for a "heavy breathing" engine.. As it gets worse, there will be Blue smoke, for sure.

Many suggestions that have worked for me over the years, but will reserve them for later. If you intend to "do the engine" at that mileage, go for it. I would try some other things first, but I am not you, and its not my car.

 

I'll do a dry and wet compression test and then I'll let you know
Thanks again

 

Hello everyone,
will update:
the spark plug of the first cylinder towards the radiator is completely covered in oil encrustations, the compression on that piston is low and improves little with the wet test despite the low mileage I think it is inevitable to dismantle the engine.
thanks for any opinion on this