So, last weeks post about a clacking noise does in fact turn out to be a dropped valve seat (#4 cylinder exhaust).
Just gave up the ghost after the car had sat over winter.
The car had the cooling sytem well sorted by the previous owner, incl. electric fans.
Ho hum...........
I had one instance of heat sink last Fall when the temp guage went to 3/4 on sitting and vapour lock occurred. Beyond that no issues.
What do do now?
I have no garage so option of doing it myself is not there, and not sure I would relish the job anyway.
My mechanic has an engine builder he has worked with for years, so I am confident in the expertise being there to get it sorted properly.

Options include just doing the head and dealing with the one dropped valve seat. Obvs the cheapest option. My mechanics thinking is that the previous instances of overheating from new remain unknown. If one seat has dropped, then he would prefer all 12 are addressed while the head is off.
Another more spendy option is go with a donor engine. Get it stripped down and cleaned and rebuilt using new piston rings, gaskets, bearings etc. Install new injectors, new harnesses etc.
I am wary of cheaping out and going with the least costly option, if similar issues are likely later.
Grateful for any thoughts on whether restricting repairs to the one dropped valve seat vs. the belt and braces approach much appreciated!

 

You could always just go for a donor head.

 

Its a thought.
Seems the labour for replacing the heads is twice the labor for removing / putting back in engine (46hrs vs. 23hrs).
Going to see if we can find a decent used engine or heads locally, as another potential option. However, probably limited chances (in Canada).

 

One thing that is making my grunnions levitate is the fact that the car has service history from the previous owner showing cooling system maintenance. Most recently the radiator was replaced in 2021 with a high capacity, triple core aluminum radiator. 82 deg. thermostats were replaced in 2016, but cannot know for sure if correct replacements were fitted. The previous owner was very detail oriented, so I would think so.
Since 2016 it has been run using Evans waterless coolant. I am ditching this, as it seems it tends to make engines run a bit hotter.
I gather that heat sink and vapour lock are not unheard of even in well maintained cars. So I am wondering about the future risk of dropped valve seats once I get the current problem resolved.

 

The V12 is a very reliable engine. Once this is sorted out you will not have any problems.
Fitting a good second hand engine in its entirety is the cheapest and easiest option.
Some new heads are still available and they are not that expensive so it is worth looking into that. A bank heads part number EBC2456 are still in stock at Jaguar: https://parts.jaguarlandroverclassic...e=900122106848

B bank heads EBC2457 may be around still too, lots on UK ebay, so are complete engines. Also worth talking to Andy Harvey at Just XJS, he has loads of stuff and at good prices. For example on ebay, heads:
https://www.ebay.co.uk/sch/i.html?_f...+head&_sacat=0



New heads are complete with valve guides.

 

Another engine, mmmm, has it been overheated, WHO KNOWS, not you or me, and the seller just wants his $$ and the engine gone.

Doing both heads is the only way I would tackle it.

Your engine/car has had some serious cooling system work done, WHY??. It was possibly overheated which gave reason for the Ally unit etc, again, WHO KNOWS.

Greg is right, the engine is trouble free in the bog picture, but "stupidity" cannot be ruled out prior to you coming into ownership.

Heads off in situ, some claim, can do, I do not.
Take the beast out, 6-8 hours for a 1st timer, engine and trans as a unit,do the heads, timing chain Boomerang, and other engine out items, like, oil leaks at the filter housing, maybe even the oil pump o.rings.



2 of mine are pushing over 700K Kms, and still as made in Coventry.

 

This could be an exercise costing $2k to $12k, depending on a minimum effort to a full bore engine rebuild.
You say you are not in a position to do any serious work on the engine yourself
Buying a second hand engine that is in good enough condition for putting straight into a car is not so easy.
Generally the bottom end of the V12 engine is robust and most owners will at least change oil and filter regularly and keep it good.
What they tend to overlook is changing coolant on a regular basis, which can give trouble with head gaskets and head corrosion.

Unless your engine has over 200,000km and/or obvious signs of neglect, I would keep it.
Pull it out of the car and take both the heads off, which hopefully will not be too difficult.
Fix the heads first. If badly corroded you can buy new or secondhand ones.
Then with heads off you can remove the timing cover, check the chain and tensioner, replace the water pump.
It would be good to replace sump and oil pan gaskets and anything else likely to leak oil.
Should be good for at least another 200,000km with regular oil and coolant changes.

 

Greg,
Thanks for your thoughts.
Yes, I found new heads online and they go for around $US700 each which is not so bad.
Labour for doing the heads is twice that for removing / installing the complete engine. By my math, getting new heads is about the same cost as going the decent used engine route.
I have found what seems to be a decent running engine online ($CAD4k) with 120k km on it vs. 150k km on mine. Currently in conversation with the owner.

 

Agreed that there is inherent risk in going with a used engine. I have located one (120k km) and the backstory to it seems genuine. Currently in conversation with the owner.
I have no garage so doing the heads myself is not reaalistic.
Yes - it had also occurred to me that previous overheating could be the reason why the cooling system was looked at previously. Not sure though.

 

Thanks for your thoughts.
The current engine has 150k km on it.
The cost of going the new head route is comparable to going with a decent used engine.
In terms of timing, it will be much quicker for my mechanic to put in a used engine vs. pulling the heads.
He was talking about doing the heads with the engine in the car, so a benefit of going with a decent used engine is that while its out we can address other issues as you say (e.g. leaking main seal etc.).

 

It’s extremely hard to remove a head without the factory head puller.
If you’ve dropped a seat do both heads or get a good donor engine
Test it by turning the engine over. Make sure it makes 4 complete revolutions.
Then do a compression test and if all 12 cylinders are nearly equal don’t rebuild.
If the rear seal is leaking it will show.
do not mix a HE engine with the pre HE ( tapered spark plugs on HE gasket on pre HE )

 

Thank you for your thoughts!
Yes, head pulling tool would be required.
The used engine I am considering has a video of when it was in the car.
All 12 cyclinders are reportedly between 215-225 psi measured dry.
It is alo a 6.0L (my '88 obvs has the 5.3L).
Not so keen on Marelli ignition, so would probably switch the existing Lucas set up on to it.

 

So latest update is my mechanic washed the car and took it for a spin. Noise barely detectable during driving?? Previously there was a very distinct diesel clatter when driving with windows up. At 3000rpm stationary it was a loud clacking sound. Now noise seems to be progressively getting quieter after a 2nd mechanic took it out.

Obvs question - can a valve seat accidently re-seat itself, albeit temporarily?
Revised plan is to drive it some more to see if noise returns.

All very puzzling!

 

That has been mentioned over the years, and I doubt it in reality, BUT, its a machine, who knows what it thinks.

Possibly, but the recess it came out of no longer "grips" said insert, so falling again is almost a given.
Damage whilst clattering around is 100%.

 

Grant thanks for your thoughts.
Yes, I agree. If it is in fact a dropped valve seat, it will reoccur. Unless its something else head related which seems unlikely at this point.

 

If a valve seat comes out with the engine running, destruction of that cylinder is near 100% likely. It typically jambs the valve open, and if the piston hits the valve, valve heads come off, pistons get holes, and often the seat will shatter, distributing shrapnel thru the intake. I had this happen on a non-Jaguar engine, and shrapnel went thru the intake into other cylinders, making a real mess.

If the seat comes out with the engine stopped, hopefully the engine won't turn over far before it jams the piston, preventing any cylinders firing and spreading destruction. I had this happen on a non-Jaguar engine, and it prevented further damage.

Either scenario means the engine stops running. They don't fix themselves.

Jon

 

The 6 litre with the Lucas ignition is a plan, BUT, you might have to swap the looms as well as the ECU as I think, repeat think, that they are not identical. Even if you keep the Marelli you will need the entire engine and ECU loom and Marelli box from the donor engine car, so that is not straightforward either. If your guy is doing the work the labour would be very costly.
If it were me:

• Engine out
• Heads off
• New heads
• Do all the things that are dead easy with the engine out, as per Grant's list

Enjoy the car!

 

Hi, if you do decide to install the 6.0 couple of things to note. The last 6.0 litres as fitted to the X305 saloon do not have a distributor drive jackshaft so you cant run the Lucas or Marelli ignitions. Unless its an engine from a pre facelift XJR-S the block will have to be drilled and tapped to accept your gearbox.Ideally get the engine complete with oil cooler and pipework. Your will need to use your existing inlet manifolds, again unless its from the xjrs. . A six litre will run ok with the Lucas 16 CU from your car but ideally should be re programmed ( see the AJ6 engineering website) to get the full benefit of the extra capacity.

 

AND

From memory, you got to be kidding Grant

The fuel lines are different.
5.3 = supply on the RH side, and return on the LH side.
6ltr, = both lines are up the LH side of the car. NOT the end of the world, but more $$ for the mechanic.

There is very dim (normal) bell ringing that the crank flange is different where the flex plate attaches, but really I dont remember.

I would hunt donw a 5.3, and simple OUT and IN.

I see many, many hours consumed with taht conversion, and as a DIY, a good thing, but paying someone, NO.

 

Thanks - very useful information!