i have finally got around to playing with my fathers HE XJS. Compression is well down on one cylinder, mediocre on another 10 and high on the last one.

I am planning to try do the work on my own but want to know if anybody has pulled a head but then had a liner move?

The number of replies will determine my need to somehow make cylinder hold down clamps

I am praying that my local Jag Owners Club (Melbourne Victoria) has one of those puller plates we all see on YouTube

Thanks in advance
Coxy

 

Coxy,

You are NEW, so welcome.

What year is the beast??

In all the V12's I have dissmantled the liners have NOT moved. Most need to be driven out from below.

The risk is there, and rotating the engine with the head/s off is a sure fire way of one or more to move, BUT, the issue with rotatig the engine is the timing chain, it will get all messed up, and jam as well, mongrel thing.

I ALWAYS set the engine at TDC #1A compression stroke, and LEAVE IT THERE. Unlock the timing tensioner, and straighten that "plastic fiasco", IF YOU ARE TRULY BLESSED, but I have never been blessed and they break, or are already broken.

This will determine the next step. If its broken, then the timing cover needs to come off etc etc to replace it, and always a NEW chain, and seriously look at the guides plates. If that cover etc is all off, then liner hold downs are a must, as the engine WILL be rotated to put all the bits "back in time" as reassembly take place.

The V12 is one of those engines that age is at them now, and that timing chain tensioner is the weak link. I dont do them now unless that tensioner is replaced, and assesing the rest as we go. Carboned piston rings is now common, as is loose valve seats (prior to dropping), oil pump suction and supply o/rings MUST be replaced.

If you are real lucky and get those cam sprockets to sit ON the "keepers" without the tensioner springing too far, then the heads can come off, and the engine can stay locked in the TDC position. Sort the valve seats, new head gaskets and good to go.

Let me know if you want more "prior" info on this task.

 

Thanks for that little Gem of information.

She is a March 1985 build with a metric engine (according to the parts manual). The car has been under cover in a well ventilated carport since the 80's and was used for long runs up the coast to NSW and the occasional formal outing.

As such she appears pretty original and that include the cooling system.
She was regularly serviced but not maintained so the Vee was a bit like an archeological dig, I kept finding bits of broken sparkplugs and a lost bolt but the loom appears to have been preserved.

She did not cost me anything but that means I have less incentive to spend big to keep her on the road.

I can get my head around dropped valves and timing chains but if it comes to lower end work then it might be game over.

Funnily enough I just snapped a sprkplug clean off a 2008 Chrysler Grand Voyager and am more terrified of that engine than the V12

I appreciate your lengthy reply and can assure you I would have stepped on that land mine without even knowing about it.

Thanks

Coxy

 

Coxy,

Interesting scenario indeed.

Low comp in what you describe is NORMAL. I certainly would NOT be lifting heads etc based on that finding.

Doing all the "normal" reactivation items (any car) and get it running. That alone will get some heat into the internals and things will sort themselves quite quickly.

Cleaning the main fuel tank, and the small pick up tank under the battery is mandatory.
New fuel pump and filter. Pump is the same as VN etc Commodore, and Falcons, so cheap and available basically anywhere.
New spark plugs. HT leads will do wonders.
The fuel hoses, ALL OF THEM, must be renewed, as they will hard and brittle and if/when they leak, BBQ Jag is quickly a reality.
Fresh engine oil and filter. I run 15W40 (10ltrs) and the filter is Z133.
The cooling system, OK many items, but to basically get it running to "suck and see" I would ensure it is FULL, and bled of air. Drain whatever is in there, and refill with fresh coolant. HEAPS of other items will need attention once you decide it is worth whatever you feel it is worth, and I do mean HEAPS.

The list continues, but it is no different to any other stored car.

Broken plugs in a Voyager, HAHA, how common is that????. We get them at work all the time, and the BA+ Falcon is right on its heals. The V12 is not normallya plug breaker, but there are silly people that do silly things, and the badge on the car means nothing. The 2 #1 spark plugs are a MONGREL, and raising the a/c compressor is the ONLY way to get then out without breaking them. Most of the spark plug breakages on the V12 are the porcelain section more that the threaded bit as in the Voyager. Please clean that V thoroughly, as any item floating aroung will go straight into the cylinder, and that is a major pain.

 

OK, based on your replies I have decided not to pull the gheads just yet and am Most of the way through replacing the plugs and distributor cap (bits are missing) and am going to fire her up.

My next aim is to get her leak free whilst at the same time follow your recommendations for other maintenance procedures.

I will be posting very very specific questions which will hopefully allow others to hone in on similar issues.

Thanks for the insight

Coxy

 

great idea to make an early Jag V12 leak free, you may be able to seal most places, but the rear main bearing ROPE seal is always a problem, like you go to all the labor and couple months later its leaking again(been there done that).

the seal is $5.00 dollars, the labor is $500.00 dollars.

Ford finally cured the problem, with a 360* neoprene full circle seal, but it requires a different cylinder block!

i found that a vacuum in the crankcase helped the most, out of most options.
using a GM chevy PCV valve.

my poor jag would be lost without GM parts.