I ended up buying a xjs (1990 convertible with the v12) over the winter and am just now getting the chance to drive/work on it some. It runs and drives as it should but is not short of its issues. The cooling needs to be addressed and im not a fan of the way the stock system works so I was planning on redesigning the whole system around modern parts. This did lead me to my first issue though, Currently the car will stay cool (at the n or below) as long as the car is moving the hood is cracked and the engine isn't working too hard. Now this was easy enough for me to do however in a moment of absolute brilliance I decided to attempt emissions on the car. This was probably pretty stupid of me as they managed to get the car abit above the n and to the point where the car was leaking coolant out of the cap (could this be caused by a clogged tube to the expansion tank?) In addition the car failed for CO (60/20) and HC (4/2) so I have to address that as well at some point. But even more concerning the engine now developed a ticking appearing to be coming from the front of the driver side bank under the valve cover. Could this be an indicator of a dropped valve seat? The car does have a ticking from the injectors but this sounds like its coming from the internal of the engine and developed after the car got hotter then it should have. Its also not really present until the car warms up abit.

 

Look into drop-in all aluminum radiators, also do the spin test with your fan clutch if the car is shut off hot and you can turn the fan (flick it the correct way) more than a fan blade or 2 your clutch is toast
I would not attempt to re-engineer the cooling system its been tried by racing teams, etc they usually went back to the dual inlet OEM style. Chances are your temp probes are 30yrs old and not great, so an IR hand held temp gauge is needed.

If you attempt to fix it all with your original rad its probably clogged with stopleak and crud, professional cleaning may be needed. Also having correct thermostats with air bleed system working, and new rad caps from Jaguar not the **** ones you buy at Autozone. Also crap gets stuck between the rad and AC radiator.

This doesn't even begin to cover the cooling system but all said if the parts are maintained (and correct parts used) the v12 will not overheat. Others will chime in but in the mean time google Kirby Palm's XJS book


The engine ticks thats normal, if you dropped a valvesat youd know it.

 

Welcome to the Forums, and when teh Jag is sorted a tad, please do an Intro in the New Members Area, keeps the "boss" happy.

That cooling system needs a SERIOUS clean out. By that I mean radiator OUT professionally cleaned inside and out side, stats (2) replaced with the CORRECT length units, ALL, and there are many, hoses replace with new clamps. Banjo bolt fiasco on the RH top of the radiator needs to sorted so it does not clog, and the pipe across the rad top panel MUST be clean on the inside.

ALL the belts replaced, Atmospheric tank (hidden behind the LHF wheel panel, needs to cleaned of MUD, and YES, that hose to it from the engine bay tank being blocked is a disaster just ticking away for some day.

The pressure cap, the one on the engine bay tank needs to be replaced, ans does the one on the filler spout (nothing special here, as long as it has a top seal is all that is required).

ALL my V12's run the system as designed, but Efans, and in our Summers, 45C++ NO issues at all, no matter how hard I drive them, and that can be very hard. I see no reason to modify what works and is simply causing grief from NO maintaining for 29 years.

Some light reading attached whilst you consume a few beers.

AND

Since you have a V12, you qualify for enough sense to read into those attachments what is Aussie and USA, and make perfect sense of it all, good luck, and many more write ups on "stuff" if you want them.

 

I've seen more than one car overheat on the dynos at Envirotest. Oh and they suck.

 

fan clutch seams fine. I was planning on replacing the rad with a all aluminum one and I was thinking of redesigning the cooling system as I planed on doing some bodywork to the car as im pretty decent with carbon fiber work and can get it for fairly cheap. I know I can force alot of air through a radiator or two so I would assume I would be able to get the coolant temp lower then stock and get more airflow over the engine. However, before I take up a project like that I would want to make sure the engine is healthy and im not sure if that is the case on this car even less so now that it developed this ticking

 

I would have said what Grant did, but also to add the V12 is a very clean engine. Something is quite wrong with the engine management for it to fail emissions. I'd start with the basics of a good tune up: oil change, plugs, timing checked etc and go from there.

 

I did also notice that the exhaust on the driver side didn't have the same constancy as the one on the other side. this is also the same side as the ticking noise. I was planning on doing plugs soon but what else would cause what appear to be improper combustion on what seams to be just a single cylinder (or a few) on just one side of the engine

 

However, the biggest issue with the XJS is NOT getting air INTO the engine bay, the factory design is more than capable of doing this. The "EXIT" air is the issue.

Main cause that I have found on many is the thick layer of foam padding/insulation up inside the transmission tunnel. Most have now fallen down, adhesive has died, and are basically sitting on the transmission, which prevents them leaving the tunnel totally, thus blocking the exit air from the engine bay.

I replace all mine with 21st Century material from a local Speed Shop, and that made more difference than any another alteration, BUT, the trans is in the way, so trans out is the almost only way for a proper job. OK, there will be some that have done it in situ, well done I say, and only you will know if you can do so.

2nd is the front lower chin spoiler, it must be in place and installed correctly, or airflow under the car to aid exit air from the engine bay, simply will not be efficient enough to keep the beast cool.

 

I would also like to note that the engine feels like it has all its horses and I never noticed any lack of power but this is the first xjs I have owned so that may be a false assumption

 

good to know that it pulls a meaningful amount of air under as well. I was definitely planning on putting some mechanism in place to pull a significant amount of air through the top of the hood when I get around to molding that and I was going to delete the bumper and pull the lower chin spoiler out farther so I can definitely take caution in my design to pull a bunch of air in that way. I dont believe airflow is too far off what it should be currently as when im driving around temp isnt much of a issue. I do believe the radiator and cooling system need to be addressed at some point though especially to be able to complete emissions where there is little to no airflow from the one tiny fan they use.

 

Many things at play here on an unknown car.

Plugs, many have had 10 replaced, as the #1 on each side are near impossible, so are left there, FACT. My HE at 120k kms when purchased, had 10 new plugs and those 2 were what I reckon were factory fitted, they basically had no centre electrode at all.

Dirty Injectors, simple dose of Injector Cleaner and a good long drive will sort that. Also, some V12's just have noisy Injectors, my PreHE is a clacker, and at 704000kms, I am NOT touching it.

Lousy oil changes, you now own that car, so you can sort that easily.

The EFI loom, sitting in the bottom of the engine "V" will be well cooked now, and is well documented as an issue. Make a new one, move it out of the "V" and the engine will luv ya.

A valve seat drop is RARE in the big scheme of things, and that CLACK is heard 3 houses away, and the engine is running quite sadly. I doubt it really got that hot, maybe hotter than you expected, but also remember that the dash gauges are fickle at best, hundreds of threads on that subject alone.

 

is #1 under the ac compressor or at the rear under the throttle stuff? I did pull one of the easy to get to plugs and it looked good but it wouldn't surprise me if they weren't all the same. I ran some injector cleaner through it when I got it and it didnt do anything for the chatter but im not to terribly concerned about that noise as it just sounds like injector noise. I am still pretty concerned about the ticking that developed after emissions it is fairly quiet but noticeable even when driving with the hood cracked and noticeable when I press on the throttle driving this definitely seams to have developed after testing as I did not notice it before. In addition at the very end of testing the jag started leaking a little bit of coolant out of the fill cap. This is the first time I have seen this car leak coolant.

 

A 1990 should be a Marelli ignition system. The distributor is effectively two 6 cylinder distributors stacked on top of each other inside a single cap. It's possible one side is misfiring or failed altogether, so I would not drive or run the car until the ignition is dealt with. If one side fails completely, you'll dump a lot of raw fuel into the catalytic converters and they typically get hot enough to start things on fire.

The system has two coils, you could also have a failing coil. My car had a weak coil when I bought it ( and original sparkplugs at 80,000 miles!) and it misfired. New plugs, coils, and wires and it all went away.

Your high CO and HC in the emissions test could be a result of misfire. I'd replace almost everything in the ignition system - wires, plugs, cap, rotor, coils and then you know you have a good base.

 

also looking at it the wires going into the coils look fairly cracked and in need of replacement so ill probably do that to. The engine doesn't feel like its missing half its cylinders at all and the exhaust difference between the two sides is very slight so im assuming its only having true issues on one or so cylinders. would that not eliminate coils, coil wires, rotor and cap as sources for that problem? (not that they shouldn't be replaced anyways) and I would like to sort out this ticking first as I have no issue replacing many parts if i know the engine is mechanically sound but dont want to be throwing abunch at a engine near death.

 

Can you post a quality audio recording of this tick? Most newer phones will capture it well enough. I can hear my car tick if i open the door while idle but...to me its just part ofvthe idle its not metal on metal just..v12 things.

You'll see it is a slightly expensive but immensely rewarding experience to right an XJS, soon it will be the most thrilling and reliable car you'll own. The list of work the guys have highlighted might seem like alot but all in it can be done in a saturday if your mechanically inclined.

 

OK, beer O'clock approaches.

That ticking, after the idiots have done what they do, may be a HT spark "tick", and the V12 has a FAT blue CRACK of a spark, and you will hear that sucker.

OR

One of the exhaust manifold to cylinder head gaskets has developed a "tick/tick" leak, NOT common, but it can and does happen. Sometimes, a simple tighten of the manifold to head nuts will shut it up, but, PLEASE, do not get silly with that tighten, or studs will break and upset the rythmn.

OR

You are up there, and have what we dont have, that is Cat Converters in the exhaust downpipes, and there are flanges, with gaskets, involved in their mounting, and those do leak from what I read at times, and a definate "tick" would be the sound.

AND

Since you mentioned way back, that this new noise appears to be on the "outside" of the engine kind of lines up a tad.

THEN

Loose spark plug/s, unlikely, but it is an alien car to you, and outside the box thinking MUST be part of this process, along with beer of course.

A stethoscope down around the manifold joints etc should pick up that tick.

The B Bank side really has nothing in there to cause a tick, the A Bank has the Timing Chain Boomerang, but unless that engine has been rotated backwards, that will be all OK.

 

I will attempt to get a video of it later today. Im hoping since it seems to appear after the engine warms up abit I will be able to get a video before and after it starts and a contrast will be heard. I will probably also drive it around some more today and see if I still notice it when driving. I have been driving exclusively with the top down for head room (im 6'7") and hood cracked so I do hear more of what the engine is doing nothing is particularly loud.


I would also like to note because I failed to mention it this car has 130k miles on it

 

and for another question any reason I cant ignore the atmospheric catch tank and just run the tube to a new clear plastic tank I put inside the engine bay? if its at the back of the bay it should be elevated higher then the rest of the cooling system and i would imagine it would function as intended. Does the stock system rely on having significant pressure from the atmospheric catch tank?

 

If I may, I would strongly suggest that the *last* thing you should be focusing on is redesigning the cooling the system.

Your car is close to 30 years old, and unless you got from all previous owners a set of meticulous records, and that within the last couple of years there was a lot invested in either time or money to getting the car properly sorted, that should be your initial focus.

For instance, from how you've described the current running state, I would bet money the that fuel injection harness is perished and causing problems. I also have a '90 convertible, but with half as many miles on it, and the injection harness had to be replaced. There will be other things that should be addressed just due to age/mileage.

The cooling system doesn't need to be redesigned, it needs neglected maintenance performed. It's entirely possible that nothing has ever been done to the system, or a hose was only replaced because it failed, not because it was time for ALL of them to be replaced. At 30 years, even with regular service, the radiator needs to be recored. One of peculiarities of the XJS is when you pull the radiator, you will be amazed at how much gunk has accumulated and is blocking the fins of radiator. It will look like a gray cat got stuck up in there.

I believe you and your pocketbook will be happier if you concentrate on getting the car sorted and up-to-date -- as engineered. Once you're there, plenty of time to see what kind of modifications you might enjoy pursuing.

Good luck, and welcome to the Forum and to the XJS.

 

I plan on doing a lot of the work to bring its maintenance up to date but I dont really see the point in repairing systems that need work when its easier to just re do them. Im not planning on keeping the radiator from this car as I dont see the point when I can go and buy a nice aluminum radiator and drop it in for cheaper. Im also really not a fan of the whole coolant overflow system so I see no reason not to do that the way I want as well.

As for yet another question does anyone know a good source for the plugs on the injector harness and plugs for the coils? I have no issue doing some wiring work so ill probably try to knock that out first.