Hey all.
I've got a problem.
I have a 1998 XJR with just over 100k.

Everything was hunky-dory till the other day when I blew a head gasket.

I haven't had the block itself looked at to see if it's cracked, but I was under the impression that being an aluminum block if I blow a head gasket it probably cracked the block too.
Am I correct in this, or might I be ok with just doing a head job on it?
Is there a cheap/easy way to know if the block is damaged?

I guess that's the crux of the issue there, because if I can get away with that I will most likely go that route.

If the block is damaged, should I replace it, upgrade it, swap an LS1 in, or just sell the car?

Thanks for any help!

 

"if I blow a head gasket it probably cracked the block too". I'm not aware of any such rule. Head gaskets can and do fail. Cracked blocks and heads are much less common, but they do happen of course.

Anyway, speculation and guesswork is all well and good, but the only way to be sure is to take the head off, and examine it and the block.

 

Is this something a lay person can determine or would a machine shop need to examine the head and block?

 

Here is what I would do.

Take the head off. If you see an obvious failure point in the head gasket, rejoice. Carefully examine the head and block under and above the failure point. If there is anything dubious, get a dye penetrant kit and check.

Also carefully check the block for distortion. You should really get the head skimmed, and the shop could check for cracks in the head at the same time.

How badly did it overheat? That is the question.

 

I have used crack test kits in the past. They consist of a couple of spray cans, and are easy to use. Do a search and you will find several. Below is one:

(HAO) Visible Dye Penetrant Crack Testing Kit | Pegasus

 

Several of us have had failed head gaskets- without any known overheat events, and new gaskets were all that was needed. Of course, you will want to get all of the tensioners and the water pump while you are at it.
I would guess you are looking at $1000. or so in parts, gaskets and fluids and about 24 man hours IF YOU DON'T RUN INTO ANYTHING! (Pros would do it faster!) I rounded a head bolt, so mine got more complicated.
A good Junkyard engine will go for about $2K, but you still have to put it in, and you may have to do the tensioners anyway.
Good luck!

 

Thanks guys.

It actually hasn't overheated.
So I may be safe on the engine block I guess.

I already have replaced the water pump a couple years ago.
Think it needs done again?

 

Fixing your engine will be the fastest and cheapest route if the head and block are OK. I'd pull the head, take it to a reputable shop that's familiar with the AJ, and get it evaluated. You may be able to get by with some head gaskets and a few other items, in which case you could be looking at $600-$1500 depending on what you replace and whether or not you can do the labor yourself.

My uncle is in the process of replacing the engine in a overheated 01 XJR he bought, so I have pretty relevant data. He paid I think $2400 for a 60k mile 02 engine, put a new water pump on for $80, and replaced the heater hoses while he was in there. So far it has taken him a couple of months of very sporadic work. I think you could do the engine swap yourself in 2 hard weekends if you really bent yourself to the task and bought an engine that didn't need tensioners. This will definitely be the fastest route if you have the tools in place to do the work, and maybe the cheapest, again if you can do the work. I'd say this route will probably cost about $3000 minimum up to about $5000 if you have to farm out all of the work. This will offset though by what you can get out of your current engine for parts, figure on maybe $600-$1200.

I have looked into the LS swap extensively, as I plan to do one when/if the AJ ever blows up in mine. Your cheapest route there would be an LM7, the Gen III iron 5.3 found in like every truck Chevy made in the early-mid 2000's, and a 4l60e to put behind it. A good LM7 will run $600-$800, a good 4l60 can be found for $500 easily, the Jaguar Specialties kit with wiring will run you about $1700, and then incidentals like exhaust, intake, and other miscellaneous stuff will be around $1000 probably. So about the cheapest you're going to get done for, doing all the work yourself, is about $4000. This will net you right around 300 hp and 325 lb-ft. You can do the cheap/easy mods like an LS6 intake and cam for about another $400-$600 depending on your scrounging skills, and that will bump you up to around 350-370 crank hp and 360-380 lb-ft. If you want an aluminum block 5.3 like an L33, figure on another $400 for the engine over an LM7. The aluminum block will save about 85 lbs, and the L33 came with better heads and a better cam out of the box. The next step would be an iron 6L, either an LQ4 or LQ9. These make more power and a lot more torque obviously, and yet weigh the same as an LM7. They will run about $2000, although that keeps creeping up, as these are very desirable to the F-body community for turbo builds and are getting harder to find. The next step would be an LS1, aluminum block, 5.7L, about 350 hp stock, easy to get to ~425 with cheap mods, and will run about $3000-$3500 for the engine. After that you're getting into Gen IV stuff like the LS2, and I'm not sure if the Jag Specialties kit can do the very different wiring of the Gen IV engines. The LS2 is 6.0L, made 400/400 stock, and can be had for about $6000 as a pullout with a 4L80e transmission. So to equal or slightly better the power of the stock engine, your cheapest route is going to be an LS1 or LS6 with some light mods backed by a 4L60e, although I'd go with a 4L80e for strength, and you're looking at about $7000 or so. But, while expensive, it's going to be much easier and cheaper to work on, will get slightly better gas mileage, and if you go aluminum block will drop a decent amount of weight off the nose. You also will be able to go MUCH bigger for less money in the future if the horsepower bug bites. It's easy cheesy to get ~400 wheel hp out of a naturally aspirated 5.7, and a turbo/supercharged 5.3 will make ~450 whp and ~500wtq easy as breathing on a dead stock engine and like 6-8 lbs of boost, all the way up to well over 1000 hp with a built 6 liter.

In summary, I'd get the head off and get the engine checked to see if it can be saved first. If it can't be easily saved and you are happy with the power of the supercharged AJ, I'd swap in a new AJ. If you want to mod your car more extensively, the LS swap adds a lot of headroom, for a high initial cost. And if all of those sound like too much work, you could always sell yours as it sits and buy another nice XJR for $6000-$8000, lol.

 

If it's just the head gasket, which is likely, replace both sides if the heads look okay, not the one side.
It has often been suggested to use 4.2 head gaskets for NA engine rebuild. I don't know if you can use them on the SC engine, but I'm sure someone more knowledgeable will comment.

 

I ain't so sure about doing both if there was no overheating event, although that is the "best practices" approach and, in fact I changed both of mine. I broke the bolt head on the head I did not need to work on, and doing two heads definitely takes some more time than doing one. I posted the picture of my gasket to show what I THINK was an assembly problem rather than a blow out. Notice the crush to the inside of the cylinder and the lack of burns across the seal ring. Other pictures from XJRs show similar failures, but I am just guessing.

Re-using the gently used water pump should be no problem, but there is absolutely no argument that the tensioners should be replaced if they are not new.

 

Spin the water pump without the belt. Check for play, roughness, noise, or leakage from the bearing.

 

BTW, if you decide to go at it yourself, you can borrow my timing tools- assuming I can get them back from the last fellow I lent them to!

 

Thanks sparkenzap.
regarding that:
When you guys all say tensioners, do you mean timing belt tensioners?
Is that one of the tensioner pulleys?

Thanks again all.

 

Timing chain (there is no timing belt as in some engines) tensioners. You're going to have to remove the chains to get the head off...and if your engine hasn't been updated (the original tensioners were plastic...and fail either roughly or spectacularly), and you're going this far down, it would be false economy to leave a proven weak point in place.

To do it right, you will also have to remove the front cover. Good time and relatively inexpensive to also do the water pump, if you have a plastic thermo housing, that too.

Just my $.02. Bite the bullet now or try and catch the buckshot later.

 

To add to Bryan's excellent advice, as he told you, the timing chains for your engine have a well known and documented defect in the tensioner design, particularly on the secondary chains. This leads to premature timing jumps and valve crashes. The upgraded parts are relatively cheap and since you will have to disassemble all of that to fix the head gasket, it is a no brainer to take care of the tensioners too. It takes special tools to set up the timing since there are no keyways or timing marks as on other engines.

Look around on this forum and you will read of a number of folks who have suffered the consequences of letting some shadetree mechanic "friend" screw this part up! On the other hand, there are several good references for step by step procedures to do it right. Note: the "zip tie" method WILL NOT work for you since you will be doing a complete tear down.

If you have a place to work on the car, and some time, some mechanical aptitude, and either own the tools or want to buy them, you can probably handle this job yourself. (Assuming you aren't a UGA grad!) If you decide to do it yourself, take your time and you can get plenty of good advice here.

 

I can confirm that 4.2 MLS gaskets fit well AJ26 SC engines. I know, since after two head gasket blow ups in two years the 4.2 ones are in the engine. The orginal 4.0 gaskets are weak and that's why Jaguar replaced them by MLS gaskets from MY2001 ( late 2000 ) and the new ones are very strong even with high boosted modified supercharged engines. Nobody should replace the orginal gaskets by another set of 4.0 composite gaskets. It would just be a stupid thing. Please remember that compressio ratio goes up by 0.2-0.3 when use thinner 4.2 gaskets.

 

Is that something I need to account for in any way?
Or is it just so I know?

 

Thanks.
About the water pump, I replaced it 3 years/20k miles ago, does it need done again?
What about thermostat?

 

Any suggestions on where to purchase the upgraded tensioners, water pump, gaskets, and tools from?

 

I should've combined all those responses into one, but I didn't.
And now I'm making another one

I'm all about getting extra performance when I can.
Are there any mods that would make sense to do at this same time, while I have the engine half apart?

I have an upgraded sc radiator and pump from eurotoys that I have never put on.
I might take this opportunity to do it as well.