So after having my 1992 facelift 5.3 V12 XJS in storage for two years due to not really being able to drive it because of work commitments, (I live in Manhattan so parking is scare) I decided to finally bring the car out of storage and take her to a shop I've been using for a few years.

Surprisingly the battery tender worked great and the car turned right on. Right before I put the car in storage though a few years ago the engine started acting funny. For one it after running great all summer, the car began to over heat often and I had to constantly refill the anti freeze so the temperature needle could stay at the midway point. After a few days the anti freeze would disappear and I wouldn't see any major leaks so I just kept an extra bottle of anti freeze in the car.

Fast forward to last week. When we turned the car on a bunch of thick white smoke was coming out of the left bank exhaust. Nothing coming from the right side.

Mechanic told me sounds like a blown head gasket and he's 100% sure of it. Quotes me $3000 for labor and $1500 for parts.

I am not going to use this mechanic and may get a guy who wants to come over by my cousin's house and do the job in his garage. Not so sure how smart that is but he quoted me $1k for labor if I buy the parts myself.

My questions are below and if anyone can help that would be amazing. I have a ton of questions and my apologies if it's too much but really don't want to give up on this car as I'd like to keep it for a very long time and keep it as close to stock as possible.

How can the mechanic be so sure it's a blown head gasket without removing the engine and head? He only has Jags in his shops from E types to some other great cars but I can see he hates working on this specific model.

What is the best head gasket set to purchase and from where? OEM? Aftermarket? Do they make better ones nowadays as opposed to when the car first came into production? Typical price?

When the engine is out etc is machining the head a must? What are the specifics of this and what is the typical cost for a machine shop to make this happen? Anything special I can do to protect the engine from having this occur again? Any recommendations for a shop in NYC?

While the engine is out, (if that's even necessary) what easy upgrades should I try to have a mechanic tackle?

I know that a big upgrade are the twin fans and a new radiator but will that really protect the engine from having this happen again?

Finally what's the typical lifespan of an engine once the head gaskets are replaced granted it's done correctly? Is this job worth it and will it give me many more years to enjoy the car?

I ask this because the car currently has 88k on it and I want to keep it original but want to make sure I'm not spending money on this foolishly.

Any help would be appreciated guys. I've gotten great help here before and it's led to some great summers with this car!!! Would be my first time trying to drive it during the winter but I want to give it a shot.

If I missed anything please feel free to chime in.

Thanks!

 

I'm going to try to answer your questions, but I'll work backwards because I have a better understanding of the later questions. Hopefully someone else will get to the earlier ones.

The Jaguar V12 can easily make 250000 miles when properly maintained. Change the oil regularly, use premium gas, and don't let it overheat. This one has overheated, several times from the sound of things. My definition of properly repaired is original condition, so if this engine is properly repaired it should last a long time.

The problem is that the head gasket didn't fail because it wanted to give you a bad day. These head gaskets generally hold up really well, they don't just give up. I would be incredibly surprised and doubtful if the head gasket failure wasn't caused by the overheating. So you'll need to fix that. If you don't fix the cooling system when you do the head you'll be changing the head gasket again pretty soon. New water pump, radiator, two thermostats, and all the hoses. If you replace all that and bleed it properly, the engine won't overheat. Twin electric fans are nice, but they're not a substitute for a working cooling system.

Removing the head from the engine while its in the car sounds like a pain in the ***. Removing the engine from the car also sounds like a pain in the ***. I haven't had to do either yet, so I can't comment on which is better. Removing the engine would give you a good opportunity to clean everything, although there will inevitably be some mission creep when you do that.

You may need to replace the head. There's a distinct possibility that it will be warped from the heat. With a normal car the head could be machined flat, but the combustion chamber design makes it particularly difficult to do that successfully. Good used heads aren't that expensive. I would probably go with the Jaguar head gaskets. Head gasket caused failures are really rare.

Your mechanic is convinced that you have a blown head gasket because you have the classic symptoms of having a blown head gasket. Lose of coolant without a leak, white smoke, overheating, the only one you haven't mentioned is milky oil. Check the oil and see if there's coolant in it. I suspect the price he gave you was high in part because he knew what was involved. Its better to come in under budget than over. I would be hesitant to have "some guy" do it, but that's me. The car is fixable, only you can decide if its worth it.

 

AGREED.

Firstly, HOW HOT DID IT GET??.
Above the "N", and on the way the "H" is NOT overheating, by a bees appendage.

The cause of the coolant loss is 100% required, before doing anything.

Get the coolant tested for combustion gasses, there are lits out there for this.

IF, and this is the sticky one, the coolant is getting into the combustion chamber, then combustion pressure will be getting into the cooling system, and over pressurizing that system, you dont mention that side of things.

The V12 is a "open deck" engine, with wet liners, so "normal" head gasket failure is a none event.

I have never had a head gasket let go, on HE and PreHE, and some of them have got DAMN hot.

Pressure test the cooling system, find the leak, fix the leak if its external, and 99% are.

That 250K miles is way too low, my experience is 500K and onward. City, shopping runs, school runs, etc etc, where the engine barely leaves idle will KILL it, fact.
Same goes for starting a V12, just to see if it runs, HAHAHA, its a Jag, be real, then shutting it down before it reaches operating temperature, BIG NO NO.

Engine OUT is the best way, as you will need to remove the timing cover and mess with that $$$$ Boomerang Tensioner. BOTH gaskets, IF it is the gasket will be needed.

Then, all the age related items, oil pump o/rings, oil filter bleed off hoses, coolant transfer pipes "top hat" seals, etc etc, can all be done easily and simply.

I suggest some VERY SERIOUS diagnosis, and make 100% sure is is what it is before laying a spanner (wrench to you guys) on it.

There is more, but I just declared Beer O'Clock, and the fingers are tired.

 

FORGOT, it happens.

When you pressure test that cooling system have ALL the spark plugs OUT. If coolant is getting into a piston area, you will see it.

DO NOT pressurise above 10psi, there is simply NO need.

 

Machining isn't always necessary but you need to check with a good engineers straight edge. I'd do a general recondition on the heads while off (I wouldn't do only one) so stem seals, reshim / check valve clearances, check the timing chain and tensioner (as per Grant) etc etc - warn your mechanic to beware the banjo bolts at the back of the heads as they strip out real easy when refitting. Replace all the cam cover bolts too - the bolts that are in originally are the type that self thread and will strip out real easy if you try to re-use - you will know because the thread looks almost triangular. If you have thae large crosshead set screws they are NOT Philips but Pozidrive 4 - a philips will strip them out as they're not that hard.

I'm in the mechanics camp here, sounds like a blown head but no harm confirming. If you 'do' need to pull the heads off then Grant is 110% correct, engine out, but this should be described as engine and tranny out, don't screw around on engine only, take the opportunity to check for corrision and clean up under the hood. If this car had a duff head gasket when put away and water got to the head bolts you won't be lifting the heads off, the Triumph Stag is a similar wet linered engine and the heads sometimes need to be jacked off using a special plate and bolts (or rope in the engine bores and a spin on the starter 'sometimes' works.

If you let the car sit a while and take all the spark plugs out (all 12) then spin the engine over while somebody watches from a strategic distance - if the car spits at you from an open plug hole then you have your answer without doing anything else.

Depending on the resources that you have available you may be able to simply lift the body off both front and rear subframes then you can play with all kinds of stuff that is usually an absolute bear (or mongrel in Grant terms) to get to - rear brakes, various bushes and pipes - starts to sound a bit like a project this way though.

If you want to know what you wil potentially be up against watch the vids in the links below - then you will know why to doubly confirm that this is the problem first - and you need to fix the cause of the overheat in the first place in any case, many regard a blown head as the cause of overheating - mostly it is not it is the result of overheating, plenty of stuff posted on here re V12 cooling - perhaps the most important system on the car ....

 

I do not believe that it is a given that the head gasket has failed. In this I agree with Grant's post above. White smoke from the exhaust is just as likely, if not more likely, to be fuel mist from a failed injector loom, shorting to earth and holding open the injectors.
Therefore, to repeat what grant advised, i would:

• top up the coolant and pressurise the system
• If you find a leak fix it and retest
• if no leak obvious, pull plugs and test for water in the cylinders.

If it really is a head job, warn your friend/mechanic that removing the heads may be extremely difficult, that is 100% has to be an engine out job, and it will be WAY more than 1000 USD of work, even on an amateur basis! Meanwhile the parts cost to you will be substantial. A known good second hand engine would be a better option, I believe.

 

Not if coolant is mysteriously disappearing as well.

Head gaskets do fail due to age without the engine overheating as the cause. I had an XJR that started drinking coolant, no other signs. Eventually, after weeks, started overheating. It was the head gasket. If the leak is only between the cylinder and the waterway you will probably not have any signs in the oil if the rings are OK. A cylinder leakdown tester (100psi) will confirm if you want to mess with it.

I would first treat the cooling system to a good quality head gasket sealer product, they do work sometimes and you have nothing to lose except a little cash. If that doesn't work just get the gasket changed. If the engine does have to come out then do both. The head will almost certainly be OK unless it got very hot which it doesn't sound is the case. It is not advisable to machine OHC heads unless it is just a face cleanup job as if the head is warped the cam bearings will be out of alignment also.

 

It has been over 30 years now however I was able to take the cylinder heads off my 197 something V12 with engine in situ without much trouble.

I did that because of a dropped valve.

I cannot remember what engine it was apart from the fact in was a V12 if that makes a difference?

 

I am an engineer by trade but the mechanic by necessity. Been working on cars for the past 40+ years and I also think you’ve got a head gasket issue based on what you’ve described. Disappearing coolant went someplace. It was either burnt in the engine or dropped on the ground or added to the oil pan. If your oil doesnt look like a brown milkshake and you don’t see anything on the ground then that leaves one option and that points to a head gasket. The smoke from start up tells me that it’s not a very big leak because if the car had been in storage for a long time cylinder cylinderWould have filled with coolant and you would have Hydro locked the motor and bent a rod. So you may be lucky and not have any damage to the cylinder head or the block surface but I would not count on that since you think it’s been losing coolant for a while.

Real easy to pull the plugs and look at the color. Coolant will turn your plugs bone white. You can also sniff the coolant in the system for exhaust gases using a $20 test kit. So it’s not that hard to diagnose. In order to do the job correctly you need to ensure the block is flat and the head is flat because if you need to mail either one of those then you need to pull the other side and match it or else your compression will be off bank bank. I would use the original jaguar head gaskets if they’re available but I also love Fel-Pro head gaskets for my older vehicles. It’s a big job and depending on the thousand dollar mechanics experience he might find midway through that it’s not worth.

 

Don't ever put any sort of sealer in the V12 cooling system. It just clogs things up and causes more problems. Really bad idea.

 

I would go one further and say unless you’re in the middle of death Valley and there’s no cell phone service and no potential tow truck coming to pick up your car and save your life I would never put coolant system sealant in any vehicle

 

Been there, got the t-shirt! I have a late 92 with 4.0 6cyl, but I think some of my experiences are relatable. Most important is have the head checked to flatness! No need to machine if the head isn't warped, and since it blew smoke on start-up you may have dodged that bullet. The mech that did it first didn't bother to have the head checked for "true". Fast forward 2yrs and I'm having another head gasket done! If you didn't dodge that bullet, there's no point slappin a gasket on and calling it good, regardless the cost.
For V12's I think aftermarket is not going to offer much, but I would buy if you find a source. OEM's are gonna require 1st male born level of cost.
If the mech that might come to you is good, he should do a "leak down" test on the other bank as well. If 1 bank has popped, check the other.

 

More problems? The engine is dead right now. An ex-V12. Have you tried it or are you guessing? Probably not. Read it on the Internet? Old wives tales? I have tried it and it has worked several times. You would just remove the engine and spend thousands of dollars without even trying it because it may block the cooling system somehow? What does he have to lose, the engine has to come apart anyway if it doesn't work ! And probably the car will be scrap because it will be too expensive to fix. Crazy mentality.

 

"Crazy mentality"?

Given the fact that the V12 can have overheating issues risking making that an even more likely issue with additives is crazy mentality for sure.

 

you can lose your radiator and the heater core from it clogging and then find one you replace the engine it overheats and kills that one too. so you replace it again along with the radiator but the crap is still in the heater core so it happens again

 

Brother. I live in Staten Island... I (we'd) have a yard here that we could work in - slowly and carefully... If time isn't necessarily of the essence, and you have a little time to get her done over a few weekends, I would love to give it a shot with ya, or a friend that I work with sometimes AND with the people on the forum guiding all - I bet we could get it done.

Free. I would LOVE to learn how to do this.

I also have a set of heads here. Although I don't know if all heads are created equally,,, we could certainly have them checked and,,, if ya like, want or need,,, have them serviced up and machined, what have ya - if you know what I mean?

You can have one of the heads. It's with all valves and springs (removed and labeled),,, no tappet blocks.

Have an engine hoist here.

By the REAL remover (video above) and let's give it a shot if all else fails...?
​​​​​​
And,,, I also would not put that additive in the v12.
That's just me.
No permanent good can come out of it.
IMHO
​​​​​​

​​​​​

 

I know New York is a long way from Arkansas. If your interested in a complete running 5.3L V12. I have an 89 Parts car I bought for the Interior. I believe it's the same as your 92, I would make you a great deal, and I'm sure we could figure out how to get it to you. Ship it, or meet half way, or ??? Mine has good green coolant in it, and good oil, ran good, no noise of any kind. will need plugs wires etc but that's pretty much a given. Engine and transmission complete $800.00 then whatever shipping costs??? Or like I said meet halfway? If interested Pm me. Hope it helps.

Jack

 

So you have actually had this happen to YOU ??

 

I would go for this deal quickly :-))

 

When you check to see if the head is flat, be sure to measure the tapper plate as well, it can warp too. Don't ask me how I know.