Either the cam or head could be out of line.

Then again, it is a new head. So, it points at the used cam as being the culprit.

However ...

Is it possible to gain enough clearance to assemble for checking the straightness by removing all the buckets and shims? That way you could tighten all the caps and see if the cam still exhibits binding. Depending on orientation, doing up only a couple of caps will tilt the cam and cause it to bind because of interference with the valves against the lobes. It even happens on the shorter V8 cam when doing tensioners.

Forgot ... a simpler method ...

Back when service manuals were on paper, cam journal bore straightness checks were done by assembling the caps and using a machinists' straight edge along with feeler gauges. The size of the bores was checked using inside micrometers. So, if the bores are the right size, and the bores are in line, the inspection passed.

And ...

On the Supra inline six, it has been seen that surfacing a warped head does not work out too well because the entire casting has warped and thus the cam towers are no longer lined up. If the head is warped and must be saved, the bores have to be built up and then line bored to regain a straight line through them.

 

Thanks for your comments.

I had been doing a trial assembly with no valves/buckets etc. The tightness seemed to be mainly with the thrust bearing cap and number 4.

I took it to the local engineering workshop where we know the guy running the show. He checked the cam and said it was effectively straight (1 thou out) which was negligible for a cam of that length. He took a thou of width off the thrust bearing cap and with a few taps on the cam with a rubber hammer it freed up. My bearing cap studs are original (I transferred them form the old head) and a couple were very slightly bent. He reckoned that was causing the cap to be a little tight.

So I have moved on and received my new shims yesterday. My clearances range from 12 - 14 thou for inlet and 13 - 15 for exhaust (I was aiming for 13 and 14 respectively).

Hoping to get the head on this weekend time permitting

 

That is good news all round.

 

Well the head has been on for a few weeks but yesterday I got to the point of start up.

Like a typical Jag is gave me a huge scare but in the end it was only a minor oversight. While cranking the motor it appeared to lock up so I obviously feared the worst but it didn't make sense as several weeks earlier I had cranked the motor several times after the cam had been reinstalled and there was no problem.

Anyway, then I realised I had only placed the battery terminals on by hand and had not tightened the clamps. Also the battery was low on charge. So I put in a fully charged battery and tightened up the clamps and it started!

The motor run very smooth, better than I ever remembered it and oil pressure was good. I haven't had time for any road testing yet (there is a newborn in the house) but hopefully sometime this week I can do some testing.

So in summary I have a brand new A bank head with new valves, reconditioned fuel rail and injectors and new injectors hoses (done my jaguarfuelinjectorservice.com) a new vacuum advance unit as the old one was seized, and a clean radiator.

 

SWEET.

Newborn, no excuse, get him/her accustomed to the beautiful sound of a Jaguar early. Sets them up for life.

Good news on both counts.

Congratulations on the task and posting back the final outcome.

 

Disaster strikes

Hadn't run the car since the initial start up almost a week ago. Today was the day I was going to take it for a drive.

Checked the oil before starting and it looked like a chocolate milkshake. Probably a Litre of water in it based on the dipstick level. I had checked the oil before the initial start up last week and it was ok but I never checked the oil after the initial test start.

So removed the coil HT lead and turned the motor over to see if it would lock up from excess water in a cylinder. No problems. Then put the HT lead back on and it started immediately. I idled it for about 10-15 secs. It idled smoothly with no sign of exhaust smoke.

So I have no idea where I have gone wrong. One possibility is that a cylinder liner to block seal has failed. I didn't turn the motor over when the head was off so didn't think I would have a problem here.

I torqued the head down in line with the workshop manual specs.

Obviously something has gone seriously wrong.

 

BUGGA.

Has the coolant level dropped equal to what you think is in the sump??.

A liner loosing its seal with the head off is NOT common, but quite feasible in real life thinking. The original "seal" was only Hilomar, which is rated as a "gasket dressing", and did the task well, and still does today, except we have better products available to us now.

A pressure test is going to show "good or bad" but if it is a liner you will not be able to see it sadly.

No water in the cylinders is a very good sign, as is the running as described.

Sadly it now looks like an engine out and reseal of the liners. What a job.

 

Hi Grant, thanks for your reply.

I added around a Litre this arvo to make it brimming full.

I note Kirby Palm's book reckons it is potentially possible to seal each liner in car with the head off, as follows:

"With the Jaguar V12, with just the heads off you might be able to accomplish several things that would require opening
the bottom end on other engines. The first possibility of note is that you can reseal the liners to the block. Use the liner
retainers (or some reasonable facsimiles) to hold 11 liners in place. Turn the crank until the piston in the one
unrestrained cylinder is at the bottom of its stroke, and then continue turning the crank while encouraging the liner to
come up with the piston. When the piston is at TDC but still at the bottom of the liner, the ledge on the side of the liner
that sits on the block will be higher than the head surface. You can then carefully clean the surface on the liner and the
block, apply new sealant, and slide the liner back into place. David Johnson actually used this method to reseal a liner
that had accidentally come loose, and ended up knocking a few more loose just to make sure they were all properly
sealed. In fact, it might not be a bad idea to turn the crank a little with no retainers in place, just to see if any liners are
loose enough to move. Or, succumb to the temptation to reseal them all whether they need it or not. See page 102 for

notes on sealants to use here."

If the engine has to come out, well I am wondering if there are reputable people out there (in Aust) that can sell me a re-conditioned V12 but at what price. I see Mike Roddy Motors claim to be experts. I am thinking that because if the engine had to come out there are plenty of other things that I should replace given the age of the motor (rear seal, tensioner, timing chain, other head etc?). There is also a limit to my available time to undertake a full engine rebuild.

But I am committed to keeping my XJS. It's my favourite car of all time and I will spend the $'s if I have to.

 

Marke,

I agree with the scribing of KP, in principle. My concern is always the age of the engine now, and you have already found previous silly things.

I would pull the engine, strip the liners, and clean all the mud out of the rear of the block, new rings, bearings, seals, o/rings, tentioner, chain, etc. The liners will be OK, as they are "super hard". Also check that other head, peace of mind I reckon.

My only concern with attempting a reseal as described is the room is limited, and the muck in there will cause you some serious headaches, coz if a grain of that gets on that seal land it will leak again.

By all means a rebuilt engine that you can really be sure is "rebuilt" would be a quicker and more convenient way to go.

The rear seal on these is not such a big issue, and if it aint leaking from factory fitment leave it be. Unless you can access the Jag special tool for "sizing" the new seal, you will have issues with it forever.

The V12 is NOT known for crankshaft bearing failure, but with that coffee brew circulating I would replace them if it were mine.

There are a myriad of things that could be discussed, but if the car is as you say to you, "do it once, do it properly, never go back there again".

 

It could just be a bad/damaged head gasket.
As I've said before, not my engine, but I don't see how a leaking liner can dump coolant into the oil.
Doesn't there have to be a leak somewhere where water pressure is greater than oil pressure (a return gallery?)

 

Steve,

V12 is a "wet liner" engine.

The cylinder head "crushes" the liner onto the alloy land of the block at the bottom, thus making a seal for coolant. This land, and the section of the liner sliding into the block are coated with sealant (Hylomar from the factory), and thats as simple as it is.

When a head is removed, the chances of a liner moving (even a few thousands of an inch) due to the loss of crush, is possible, even without turning the engine over at all. Sometimes they reseal, mostly they do not.

At this particular area there is NO oil pressure, only coolant pressure, and gravity.

 

Thanks for the explanation, Grant.
MF tractors (no offence - just what I know about) use the same system with an O ring seal so you can reline them 'at home'.
I can see how this gets combustion gas into the coolant with loss of compression but how does it get large amounts of coolant into the oil?

 

Steve

Doesn't the coolant enter the bottom of the cylinder on the upstroke, through the minute gap at the bottom of the liner, and fall down past the crank into the sump?

Just an idea...

Greg

 

And a cunning one at that but wouldn't it end up on top of the piston during induction when the chamber pressure was < coolant pressure and then be blown back during the compression/ignition phase or be blown out of the exhaust on the exhaust stroke?
I don't know, just theorising on a damp Sunday morning.

 

The seal at the bottom of the liner fails, and water simply flows into the sump. It is all below the piston line, even a BDC (bottom dead centre).

Renault used a paper gasket of varying thickness to give the correct liner height "above" the top deck, so when the head was tightened down the "crush" made the seal.

Peugeot used a copper ring, variable thicknesses also for liner height adjustment.

Jaguar did not use a seperate seal, relying on the liner actually "crushing" onto the block machined land to give a seal, and the Hylomar took up any variations. When I rebuilt mine I swapped liners form hole to hole until I had a consistent liner height I was happy with, and Hi-Temp Red RTV used as a sealing agent.

 

Right, I understand.
OP's going to have to take the liners right out then, presumably.

 

Pretty much.

Lots of theorising about resealing them, but when you actually get in there to do it, it is really theory. Then add to that, the age of the engines now, patch up will always be the weak link.

 

There have been further developments with my XJS, for the better it seems -

After noticing the milky oil I drained the oil and left the oil bung out with a small tin under it to collect anything that wanted to drain out. I then filled the radiator until it was brimming with water. Over the course of a couple of days it required very small top ups until it reached a point when it stayed brimming full. No water found its way out the oil drain. So the small water top ups must have been as small air pcokets were dissolved.
Then I purchased the cheapest oil I could find (Woolworths homebrand, A$16 for 4L) and filled the engine with oil. I run it in the garage for a total of around 15mins over a couple of days. There did not appear to be any water loss and the oil stayed fairly clean ( a little bit of water residue from the old oil and what was in the filter) and the engine ran well.
I then changed the oil again (cheap oil) and also changed the filter. I have now done around 200km in the car over a couple of weeks. So far the oil is perfectly clean and I've had no water loss. The engine also runs well. It was hunting slightly but I tightened a hose clamp on the hose that provides ECU vacuum and that appears to have cleared it up.
So I have the mystery of how water got in the oil but no longer appears to be? Maybe the water got in when I initially removed the head but I didn't think it had based on the dipstick level. In hindsight I should have done an oil change prior to the initial start up but in my haste to test the motor I didn't.
Anyway I will enjoy driving my V12 and hope that problem is behind me

 

Well done.

Many theories on how it got in, and now it dont, so basically history, and best left there.

Enjoy the drive.

 

I did not read the whole thread, but here is my 2 AU cents.
Replace Oxygen sensor on that side and see what happens.