Hi all…. Looking for advice. My mechanic said my 1990 Jaguar xjs v12 has a blown head gasket. He said it’s a hassle to fix and basically said he’s not willing to do it. This is “yorks and lance” in chatsworth,ca. My question is if anyone knows anything about getting a head gasket repaired and if it’s worth it. I’ve had the car for 5 years, it has 45k miles on it and I’ve already spent thousands on repairs, upgrades,etc. I put in a better stereo with blue tooth, tinted the windows, and had the paint detailed, etc. I live in LA and even here, I get compliments all the time when driving. A woman in a Porsche 911 pulled up next to me one day and said she loved my car… I am stuck as to what to do. I’ve heard I can get the engine swapped with a Chevy v8, but have no idea where to do this, etc. I love the car and want to keep it, but can’t keep sinking more and more into it. It seems something is always going wrong. I had the entire cooling system repaired, so I’m confused as to why it overheated in the first place. I’ve had all the belts replaced, filters, fluids, etc. i spent thousands having the steering fixed, radiator hoses, pump gasket, heater valve, heater hose kit, drive belts for AC and alternator, air valves, brakes, replaced all 4 differential bushings, new power supply cable, etc. I was told I need a transmission rebuild also. Anyways, I had more done, but too much to list. It sat in the shop during Covid for 5 months as parts were hard to get. I do love the car, but am tired of the constant money I keep dumping into it. I know they require high maintenance, but this is getting too much for my wallet. How much is a conversion in general and does anyone know a good place in the LA area that could rebuild an engine or do the swap? Thanks so much… ps… the paint is flawless and interior like new. The car looks incredible and is so fun on the coast with the top down, but I’ve been left stranded a few times as well, like this last time when the head gasket blew. I welcome all suggestions or advice on what to do…. Thanks so much everyone. I bought the car for 12k and have put about 8k into it so far and now the head gasket is blown, so I’m just very depressed about it as the money going into it seems never ending.

 

My first advice would be to get a second opinion. Or at least ask your mechanic how he knows the head gasket is blown. How did he test for this? Or what did he observe that makes him say it's a blown head gasket?

What symptoms are you experiencing?

Blown head gaskets can happen on a V12 but it isn't actually all that common

Cheers
DD

 

I totally agree with Doug. How do you know, or if you do not know, ask the mechanic how he knows the head gasket has failed and post the answers here for some experienced feedback. At 45k miles a head gasket failure is unlikely.

 

You could do worse than reach out to the LA Jag Club. See where they get their cars fixed. Go to one of their shops for a second opinion.

HTH, Dave

 

There are several excellent shops in San Diego but the work is still complex, for sure.....20k is not an excessive investment in a classic sports car, just ask any Porsche owner
It would be hard to find something as satisfying for 27k in the open marketplace, so your investment is within a reasonable range
I would agree that a blown head gasket is a rare occurence on these cars, so a second opinion would be prudent

 

479 CI Big Block Chevy. 540 HP.


lots of room to work on it

Cold air intake from the cowl

The current swap is typically an LS motor, they are reasonably price, will blow the doors off a V12 car and conversion kits are readily available. They weigh less than the V12, so you may have to use different front springs, or cut a partial coil off of them. I see you are in CA, you still ahve to meet emission standards so an LS is the way to go, but investigate what hoops you need to go thru. I believe you have to meet emission for either the year of the motor, or the year of the car, which ever is newest. Google jaguar v12 to LS conversion kit. Someone in CA makes these, i believe, they can answer your questions.

Doug

 

Before jumping in complicated story of head gasket, i know that there is one chemical simple test. You should find it in some shops. The test is with the coolant to add in a bottle where the reactive chemical will change colour whether the head is blown or not. Probably something that reacts to anything mixed in the coolant even if there are not visible leaks of oil or exhaust gas mixed in the coolant. At least you'll get a real view if it is or not head gasket. I also saw on another one website that there is a plate somewhere in the engine where sometimes a mix of coolant and oil may happen and btw many mechanics will think about head gasket. i would suggest to check this before spending heaps of money.

i don't known exactely if the v12 has the same part but it could be worth to investigate.

https://www.xjsbanger.co.uk/jaguar-aj6-3-6/4-0-engine-head-gasket-delusion

and the test i was thinking about

https://amzn.eu/d/dOYe27I

 

I’ve heard I can get the engine swapped with a Chevy v8, but have no idea where to do this, etc. I love the car and want to keep it, but can’t keep sinking more and more into it.

I would never recommend a V8 swap for a number of reasons.
The cost of that swap, IF done right, would be more than a head gasket fix.
45K miles is unlikely to be a head gasket failure unless something catastrophic happened.
Bring it to another shop to diagnose what is going on.
Same thing with a trans rebuild, the 480 LE trans should not need a rebuild, unless.....

 

Did Yorks & Lancs do the cooling system work? If so, something doesn't add up. If I owned a shop and you blew a head gasket after we did the entire cooling system, I'd be apologizing and replacing the gasket without charge.

 

boy did you get that right!!!!

 

I would agree but the timing of events isn't really clear to me. Was the cooling system work done immediately prior to the current situation....or several years ago?

Cheers
DD

 

I would ask why he thinks it is a blown head gasket. Is it blown to the outside or inside with combustion gasses and coolant mixing? There is a pretty simple test that will show if there are combustion products in the coolant, which indicates a blown head gasket. Less than $30 at Autozone if you want to confirm this yourself. Other than what I saw on York's and Lance website I don't know anything about them. Their specialty is British cars so they probably know what it takes to replace a head gasket and they just don't want to do it. It is a lot of labor hours and unknowns. The head may be warped and need replacement or need to be planed at a minimum, which has its own problems. If you are into it that far you should do a valve job. If much coolant mixed with the oil it will make a mess of the oil passages and require a complete rebuild.
If it was my car, and I confirmed the blown head gasket with oil and combustion gasses combining, I would probably look for another Jaguar 5.3 V12 motor and swap it out. You should be able to find a Jaguar 5.3 v12 for $1000 to $2000. ebay, Craigslist, Jaguar Heaven, etc. It will be less expensive than lumping it with a Chevy motor. And you still have a real V12 Jag.
Bottom line, keeping any old car on the road takes a lot of labor. Google says Jaguar repair shops charge $150 to $250 per hour for labor. I cannot afford to pay that so I have to do the labor on my cars myself if I want to keep them. It may be time consuming but it is not that hard.
You need to take a hard look at the car and decide if it is really worth fixing. If it is in great shape I would do it. If it is just so-so I would not waste time or money fixing it.

 

When the job is being done, make sure the head is flat. If not, you will blow a head gasket. Also, make sure the tappet bloc surfaces are parallel. Yes you will have to adjust the valves.

 

Not that easy. These are linered blocks and not only do heads need to be verified but so does the deck of the block and liner hieghts, it would be stupid to do only one side, don't for a second think you're doing a V12 in situ, if the head has blown of course, there needs to be serious investigation if it has into why, heads usually go for a reason, if it has been overheated the valve seats need some serious scrutiny. Anything requiring taking the off head will require attention in so many areas, and getting the heads off can be an exercise in itself that if you don't DIY the bill will be significant - got to pay to play.

Adjusting the valves not necessarily, good to check for sure but these aren't pushrod engines the valve lift is governed by spacers in the head and won't change if the face is skimmed, it will change if the valves are reground though - but it is common sense to check clearances it while it is all open.

I've had my engine out and can empathise totaly when a garage says 'not interested' - most garages work on volume and this would tie them up for weeks assuming they even had the abilities to sort a V12 - not all machine shops are worth a damn either so the consequences of opening up a V12 are high risk.

 

Definitely get a second opinion. Case in point: 13 years ago I bought an immaculate 1987 XJ-S with 40k miles for $1000 because a shop had told the previous owner that it had a blown head gasket and given him an astronomical repair bill. I had no reason to believe the shop's diagnosis was wrong. When I got it home it turned out to be a failed radiator cap and after bleeding the cooling system the car ran perfectly.

If you do take it in for a second opinion, bringing all your receipts from the other shop will be of great use to them. If the worst turns out to be the case, finding a used V12 will be the most straightforward and cost effective repair. V8 engine swaps vary widely in quality of execution and a good one will cost considerably more than a used V12. Also, being subject to California emissions testing, you will likely spend the rest of your days jumping through bureaucratic hoops trying to get an engine swapped car smogged here, if it is even possible at this point.

I would argue that the folks on this forum have a greater depth and breadth of knowledge on the XJ-S than many shops on the West Coast of the United States. If you provide more information on what you are experiencing with your car now, and the history leading up to this point, I'm confident they can give you sound advice.

 

I concur - what symptoms are present that would make a head gasket issue the prime suspect ?

Rad caps - interesting point - there are two and they should be different pressure ratings but many don't realise this including so called 'shops', the higher pressure rating goes on the crossover / bleed pipe. Air leaks can also cause overheating which in turn blows heads and drops valve seats as can poor fuel pressure, thermostat issues, overly advanced timing (or wrong fuel - pre ignition or worse detonation), crud in the cooling system through failure to use appropriate coolant aka water only or even Jaguars insistence when these cars were common of using BarsLeaks rad sealant habitually, chocked radiator internal or external, fan none functioning, or even an air locked coolant system. Very often the head gasket is blamed for causing overheating but it is generally overheating that causes head gasket failure not the other way around.

I'd be a little cautious on supplying detail of what has been done - I'll offer the reasoning.

• It can cloud the diagnosis / opinion following 'it can't be that' - really - don't be so sure
• Mechanics in the majority these days are screwed if they don't have a laptop for diagnosis - the old skills are disappearing fast - if you can't diagnose one of these cars without OBD etc it's not the car you should be working on.
• A good shop will be able to spot where 'fingers' have been.
• Very often the engine isn't the issue but one of the myriad of complex support systems these engines have all of which must work correctly
• The chemical 'colour/color' change kits only detect exhaust gasses in cooling system but aren't always conclusive
• Pressure stability testing cooling system type tests are also inconclusive

Need to make the person investigating go back to basics ... not go in with a pre-concieved notion / confirmational bias

There need to be at least two tests, one of which should be a leakdown test - not much fun on a V12 and very time consuming - putting air pressure in a cylinder is dangerous, the crank cannot be allowed to turn backwards and holding the crank by hand is going to guarantee an education that you won't forget.

A used V12 is a can of worms - you still need to tear it apart because you know nothing about it - that's a big engine to remove with a lot of places where things can go wrong only to find out that it is worse than what you took out ....

I'm a bit of a purist and V12's get a bad rap because either the wrong people own them (can't run one on beer money and no maintenance) or the wrong people work on them and do so inappropriately. I am not a fan or supporter of engine swaps but your car your choice.