Blown head gasket @ 140K miles........................

[Brakebuster]

Phil ( Charlie5 ) has a 91 3.6 XJS , and after all the time and effort getting the mechanicals sorted he has been enjoying his car , unitll last week , poor starting , poor running , huge loss of water , water and steam coming out the exhaust , pretty sure its a head gasket issue, and as the car has covered 140k miles, then its not fully unexpected

we are currently in the process of collecting parts together to rectify the problem, this is mainly a genuine Jaguar gasket set for the top of the engine, this is every seal and gasket required , we will also change the water pump , and put a new set of plugs in and it will obviously have a full oil and coolant change when the work is done

out of curiosity , i asked my local Jaguar dealership how much this work would cost, they came in at 15 hours at £100 per hour plus vat, plus parts , totalling about £2300 all in , this is not realistic given the age and so called value of his car, and he has asked me to do the work for him , i am happy to do this especially as Phil will be using genuine parts all round.

as i'm on holls next week there will be a slight delay , but I'm expecting two consecutive weekends providing there are no major issues once things are taken apart

does anyone have any tips on the work and what else should be replaced while we are in there , bearing in mind we want to do this at a sensible price

the gasket set comes with ' valve stem seals ' i think these are the rubber type rather than brass tubes ?? , how easy hard are these to do DIY , or is it a leave them alone job ?? would it be worth outsourcing the head for skimming and finishing etc ?? cost ?? we are looking at all options at the moment.

i have been looking at the heritage parts, and can get most of the timing chain guide and slippers for about £100 , i think this would be be beneficial providing its in the budget , unless there is nothing actually wrong with the ones in there already ??

Phil is bringing round his 3.6 Jaguar ROM tonight for me to carry out some light reading on the subject,

wish us luck!

BB

[ptjs1]

BB (& Phil),

Good luck with the work. I've not pulled a 3.6 head but here's my thoughts:

- Change all the rad hoses whilst it's all drained anyway. Best time as always
- Check the metal coolant pipe mounted under the inlet manifold. Even if it looks fine, take it off, change the bolts and possibly the pipe itself
- As usual with an XJS, consider rad core replacement if the fins are less than 100% perfect
- Have the head skimmed. If you're not going to do that based on the head being perfectly flat as measured accurately, at least check and resolve any deterioration at all on the cooling passages, particularly on the back 2 cylinders. It's often considered that it's hotspots that develop on the back cylinder or two which causes the head to eventually let go on these engines
- Check the exhaust manifold with some uv for any cracks at all and replace if in doubt. Even the disturbing of the manifolds can set off a crack that's ready to go. Very prone on these engines
- Clean the airflow meter carefully
- Use electrical cleaner on airflow and other elec joints whilst apart
- Change the lambda sensors unless they're only a few years old. Will make a difference to the running and much easier to do whilst all the exhaust is off etc
- Change the exhaust manifold nuts
- Check the spray pattern on the injectors
- New plugs and maybe leads

Have a good couple of weekends!

Paul

[vernon]

Hi, join the club,
my Xk 4.2 engine done about 150,000miles has blow the cylinder head gasket. The valve gear on mine a bit noisy, so needs re-shimming.
And I hope there are no cracks in the head.
Keith at xjrestorations is doing mine, goes in Wednesday, so I will keep my fingers crossed.
Good luck with yours.
Vernon

[PaulGover]

Dunno about these new-fangled 3.6 engines, but replacing the timing chains was reckoned to be cost-effective on the old XK engines.

[pjn4200]

Hi, I've changed a few aj6 & aj16 head gaskets. It's relatively straight forward but the head is heavy so care must be taken when removing and refitting. All the advice given so far is worth following.
I recommend changing the headbolts and the water hose below the inlet manifold. Also you need the four camshaft lock tabs which are very cheap. Keep a note on the shims and valves so they can go back in the same place.
It's well worth changing the valve seals and decoke the valves.
If you want to go further then the timing cover can come off to change chains any guides but this starts to get expensive but its easy.
There's nothing difficult but it just all takes time hence the crazy jaguar dealer prices.
Good luck.

[PaulE]

Hello BB,
When my 4 litre AJ6 went the head studs were on the list to be replaced with new as a routine item. Not sure whether the 3.6 is the same but worth checking. Seem to remember that there was a special procedure for tightening the head down too, something like running the nuts up to a certain torque figure then another 90 degrees; again worth checking. The gaskets for the 4 litre have been redesigned I am told and are now more blow resistant- something about a compressible ring around the cylinder perimeter. Best of luck and do report back.

[PaulE]

I see that in the recently published Practical Classics 'Guide to the XJS' on pages 67/68 comes the regular and now expected phrase 'there can be head gasket issues' which has become a regular in all reviews of these engines. Sadly quite a few of us know that, and I see above that the estimated cost of repair has now climbed to a remarkable £2300. Can failure to look after the anti-freeze concentration and a few leaves in front of the rad really be the whole story leading to these failures? I personally know several owners who have had the problem so it must be quite widespread and it would be nice to know if there is a lasting cure.
I was told by a reputable engineer that if you have repaired the head properly you should not have it go again, so that is something, but an analysis of the trouble and the cure is needed. Has the gasket sealing been redesigned for instance?