I have pretty much completed the rebuilt of my 4.2L liter engine (documented in another thread in this forum) and it is now connected to an engine test stand. I have filled the setup with coolant (50/50 mix of DEX-COOL and distilled water) and right off the bat I noticed seepage from the cylinder head gasket on the passenger side - clear as day light. I drained the coolant and removed the cylinder head bolts. One by one I removed the studs, inspected them and re-installed them. I then followed the torque tightening sequence as described in the book. I have ran several cycles of the tightening sequence at 25ft.lbs, 35ft.lbs, 45ft.lbs and finishing with 52ft.lbs. I was methodical and very meticulous. I used a SnapOn torque wrench.

I added the coolant back in and seepage was gone. I then pressurized the system and seepage came right back, same spots at about 7psi.

The head and block were straight before I assembled them (or so I thought). Now the head gasket was floating around the shop for a year before it was used (new of course). It is hard for me to believe this but I am suspecting a bad gasket. We are talking brand new, fresh rebuilt here with fresh parts and gaskets. The engine was fine before taken apart other than leaking oil from every conceivable mated surface and burning some on top of that.

I am open to thoughts...

 

Thoughts:
If a 'new' gasket was "floating around for a year" in our shop it would Immediately be suspect! However, in that Clean Room you call a shop, it would be a stretch of the imagination to say the least. Then again.....

If you had the head plained or otherwise machined it's possible a metal shim gasket couldn't conform if machine marks are too deep. And it might not hurt to check it with a machinist's straight edge anyway, not only length and width but also corner to corner both ways, block and head both.

We used to spray metal shim head gaskets with a copper sealer called Copper Coat and never had a head gasket failure after using it. I've heard there's an aluminum one too but I have no experience with it. (The Book calls for "Jointing Compound" whatever that is.) Of course I've never worked on an XK engine so all this may be moot.

However, by now you should be very proficient removing and replacing the head, and a gasket shouldn't be all that expensive, so why not ditch the one that was "floating around the shop for a year" in favor of a brand new one and try it again after checking for flatness.
(';')

 

Just a thought or two...
When you removed the head studs ,..did you clean out the coolant that would have dribbled into the holes deep down in the block ?? Coolant in these holes will provide false torque readings as you are trying to compress the coolant in the holes. As well are you using "acorn" nuts on the upper end of the studs to tighten the head down ? If so make sure they are not "bottoming out" before the correct amount of torque has been applied.
Did you check the block for cracks prior to rebuilding it?
I feel that, if the head was sent out for refurbishing ,.. any good machine shop would make sure it is not warped and the final finish is at factory specs. Is gasket on correctly? I use the Copper Coat as mentioned previously as well - good stuff. After my own past experiences with the long head studs I feel they are the weak link in the Jaguar method of containing cylinder pressure and preventing coolant leaks unless the block is cracked or the acorn nuts are prematurely bottoming out due to some other ailment.

 

I second all of the above. Especialy, the checking of bottoming fasteners.


And, yeah, another gasket. Even f the one you used, twice now, was good, it may no longer be good. Taken a set....


Carl

 

Thanx for the thoughts guys, appreciate it.

So, yes the block had been check for cracks. None were found. The cylinder head I rebuilt myself and checked straightness with a machinist edge. The block was bone dry when I installed the gasket and new studs. I put the longer studs in the right places. I checked the bottoming. That was the first thing I did. The studs extend about 16mm of the top of the head (long ones a little higher ) and the acorn nuts bottom out at 25mm. That seems not be the problem.

Now Copper Coat. Never heard of it! Need to look into this and possibly use it next time. Any tips on that will be appreciated.

I got discouraged last night but I am recovered now. I ordered a new gasket set from SNGBarratt and will be tearing the engine down, again. This time just enough to remove the head. I will take it to a shop to check it for trueness.

Wash, lather, rinse. In this case, repeat.

 

I hope it works. You did a beautiful job on that engine. i watched the thread with envy.

 

Copper Coat comes in a spray can. I find it good for holding gaskets in place while fastening parts together... acts as an adhesive.

 

Are you absolutely sure it was the head gasket and not the inlet manifold gasket leaking ? There are coolant passages against the inlet manifold gasket, (I'm not sure how many), but clearly if these leak the fluid will drip down opposite these passages. Might be worth a check, you never know.

 

Lagonia, don't know if you come on here anymore, but if so, did you ever find out why you had the leak? Did it get fixed? How?

I read your two threads here and it was like a good book where the last pages are missing.

 

I am planning to finish this book for sure. I hate unfinished books myself. It might take a little while but it will get done.

The engine is still on the engine test stand in a corner of the shop - I have not done anything to it yet but I am planning on it. Since my last post I got a Mercedes 560SEL, a Jaguar Mark 10 and a C3 Corvette. I do keep busy and, unfortunately for my pocket book, I like variety.

 

Ahh. well thanks for that. I am considering what I need to do for my new to me XJ6 and am trying to learn as much as I can before I turn a wrench.