I have a 1986 5.3l V12 with 60,500 miles on it. Once it is warmed up it runs great for hours and does not get too hot. So I assume the engine block itself is good.

When I start it on a cold morning it barely stays running. For the first few miles it takes on gas intermittently. It used to idle up and down too. Once in a while it misses a few times.

So instead of fixing one problem at a time, I am wondering how much it would cost to go through the entire spaghetti mess ontop of the engine and replace everything that should be replaced on a 30-year old engine including spark plugs, distributor cap and dried out vacuum lines.

Would that approach yield me a reliable smooth-running engine for a while?

 

DIY labor?

Or pay $100/hour labor at a repair shop?

Cheers
DD

 

$100 an hour. Until I learn how this little monster works. It quite a little bit more complex than my Beetle engines.

 

Considering the experience of a typical mechanic, they may not know how much is required to make the v12 engine reliable. Don't forget that all the coolant hoses need to be replaced along with the thermostats and a good coolant flush.

There are little details that you can glean from the forum that should be done that are not typical of a common tune up. For example: the rotor on the distributor probably needs attention- it just requires a couple drops of oil, but this step seems to be generally neglected by mechanics.

The auxiliary air valve may be sticking, and these can be cleaned even though they are just intended to be replaced. This could assist with cold weather startups.



Another important aspect of doing the work yourself is that you can spend time to clean all the gunk and debris out of the V when you have removed some of the obstacles out of the way. That time adds up fast.

 

God hates a coward ! You learn by doing ! Just teasing; I hear ya. There are some things I don't jump into as well, even after an entire life of tinkering with car. Automatic transmission overhaul, for example.

Anyhow.....in an attempt tp answer your question.....

What you're referring to is what we commonly known as 'doing the vee':

- replace plugs, wires, cap, rotor
- fabricate a new fuel injector harness
- replace intake gaskets
- replace throttle bushings
- clean throttle bodies and adjust linkage
- replace vacuum hoses
- repair numerous cooked wiring connections
- replace injector hoses
- rebuild fuel feed and return hoses
- repair AAV
- clean air injection tubes (or remove 'em)


I'll throw out a number and we'll see what others have to say.

20 hours labor.

Cheers
DD

 

I am in the processs of replacing most non-metal parts in the engine bay of my 92 5.3 as preventative maintenance. I do this with any new to me XJ. That means a rebuilt wiring harness in the V, all new hoses, and new gaskets from the valve covers up as well as basic cap rotor filter tune up stuff. I probably have $800 into it. Injector cleaning was $225, the cap was $100, heater hose kit $100... it adds up fast. Labor wise, if I wasn't doing this myself, I wouldn't have bought the car.

 

How did you learn how all the spaghetti mess ontop of the engine works? Is there any good documentation out there? So far I have the green repair manual and the SNG Barratt catalog. Looks like I will have to learn it or go broke. :-)

 

"Learning how it works" and successfully doing the repairs are two different things.

Some of us have been playing with these V12s for years and are still learning how everything works. But that didn't stop us from making the repairs.

When working on a V12 slower is faster, if you get what I mean. Try to hurry and the car fights back. Resign yourself to the fact that lots of disassembly is usually needed to do any repairs. Don't fight it. Just go with it. Take lots of notes and pics, be very methodic and organized. Don't be intimidated by all the 'stuff'.

You'll come across things that really make you wonder "What were they thinking?" but that's normal. When working on old Jags remember that there are no engineering defects. Anything that has the appearance of a design defect is, in fact, merely "an interesting design feature".

IMO, there really is a 'mindset' aspect to repairing these cars. You gotta get into the spirit of things.

It's a challenge, but very gratifying in the end, trust me. There's a real sense of accomplishment ...and a well-sorted XJS is an absolute joy.

Cheers
DD

 

I first learned about these cars when I got an '86 20 years ago... I was 19. Spent every penny from years of grocery bagging money on it, $6000. Took it to get a state inspection and they came up with another $6000 in repairs it needed. Got on Jag Lovers and ingratiated myself with Kirby Palm and crew and learned how to fix the damn thing. Here I am almost 40 years old and still playing with them. I'm not half bad anymore but still post questions regularly!

Basically... if it's not your basic transport, go ahead and break it for a few months and do this stuff. But maybe in the winter, not prime driving weather like now!

 

I'm still working on this, but here's a "short-list" of engine components that I'm working my way through. Pricing is just based on my purchases or searches and may be wildly different based on source, model, or your location. It can at least put a broad scope on the hardware costs to add to your estimate.

 

To make the car really reliable I would add to this list: replace all coolant hoses, replace ignition amplifier, clean the resistor pack plug and socket, renew coils, renew TPS, simplify vac lines by removing the lot except one directly to the distributor vac capsule, replace distributor vac capsule, lubricate dizzy advance springs.


Then you get to the running gear...
I think 20 hours is a bit of a low estimate, it would take me about two weeks to do Doug's list, most of mine would not add much time as it would all be apart. If you have somewhere under cover to work, essential, I really do think you should do it yourself unless you have an acknowledged V12 expert on hand. If you divide the work up into sections, and ask us all for details on how to do each section, you will be able to do it. What is more, you will understand the car as a result.


As a plan, to get the car right, you have exactly the right strategy in my opinion,

 

I knew I was forgetting something !

Cheers
DD

 

We seem to have all forgotten belts. Needs four of those!

 

Something I've said before here is that the V12 isn't a complicated engine. However, there is lots of it. That alone makes it intimidating. Just break it down into the systems and it all becomes understandable and fairly simple actually, there is nothing particularly difficult about the V12 over other engines.

Just remember the phrase "you can only eat an elephant one bite at a time". The V12 is kind of similar, look at it in small pieces and it's easy.

 

To get to your initial problem, it sounds like your axillary air valve is stuck. Replace that you the cold start should be much better.

 

Or unstick it. Remove it an soak it in some PB Blaster as a first try. You'll need a replacement gasket though to re-install it.

 

Is there anything special needed for replacing the spark plugs? Or is a spark plug socket and a socket wrench all that is needed like any other engine? I've worked on old Chevy's, an MGB, mid 80's BMW, Late 90's BMW's but none of them have the plugs INSIDE the V. They all had theirs on the outside of the heads just above the exhaust manifolds.

 

Depends on the car. If you have the GM A6 air conditioning compressor, take the compressor out ( I think 4 bolts + belt) and set it aside gently. I have a piece of plywood handy that spans the gap between the radiator top rail and the engine and set it on that.

There is enough slack in the hoses that you don't need to discharge the refrigerant. Then the front 4 plugs are easy to get to. It's quicker to remove the compressor and then do the plugs than to try and work around the compressor.

If you have a later 6.0 car with the Sanden compressor there is enough space to work around it.

Otherwise, there is nothing special needed to remove the plugs. I always take an airline and blowout the plugwells before removing the plugs, just to remove any debris in there so it doesn't fall into the cylinder.

Use NGK plugs, they are what Jaguar recommended. Use the normal ones, not any fancy precious metals. Gap to 0.025". They are taper plugs, so seat them sung and give 1/16 of a turn to tighten.

 

The best thing about Jaguar is the people like the ones on this forum and everyone else, and the people who have literally hand written 800-page books on everything related to this car.

Lots of experience here, I probably owe Doug a drink for the number of times his suggestion is spot on for issues I've had, and just reading the forums you can see how people do things then try it yourself, its a remarkably simple engine you don't need a laptop and proprietary tools to fix it.

 

It's easy for a newbie owner to be overwhelmed . . . so I agree with advice to tackle small tasks, one system at a time. For example, what appears complex is still all about optimum fuel/air mixture delivery, timing, healthy spark and electronics, and well maintained internals . . . and all under the monitoring and fine tuning of the ECU.

If you start on the fuel/air systems, I see the logic to clean or replace your AAV if stuck. Ignore all else until you test for any improvement. An alternate plan is to focus on electrical items, connectors and wiring. Note the emerging corrosion around your amplifier fixings. What is the condition of the connectors? . . . dull, loose, "salty" . . . or bright and tight. In particular, check connectors at relays and all ground connections. Once again, limit to a somewhat related handful, ignore all else, and test again for improvement.

Once you hit a snag, and you will, post here. There are plenty who will dive in to help. So, go for it . . . DIY may not be for everyone but it will do far more than save you money. As you gain confidence . . . then may be the time to tackle "the vee".

Best wishes,

Ken