Hey all!

Within the last few weeks I've bought and got running my first ever project car of an XJ40 Sovereign and am now in the "make it run better" stages and have hit a few snags. Just to note; I'm not of a mechanical background nor used to nuances in terminology just yet so if I mislabel or ask something stupid...feel free to laugh!

First off, the engine runs pretty well from what I can tell, however it becomes extremely warm (from touch and from smell) within just a few minutes, or a hundred metres of travel (if that). The metallic structure attached to the engine below the spark plugs appears to be the part which gets hottest (that could just be because it's metal), but it's definitely far too hot for how short of a time it's run. The car is full on coolant (the last owner said it had been changed around a month ago at this point), oil seems "within range" (above the top edge of the checkered pattern on the dipstick, which I assume means it's got a lot) and the oil temperature gauge...doesn't move (I've done research and seen that somewhere along the line is a regularly dodgy part in these Jags, so I'm not taking it being cold as gospel). I'm considering that I'd likely need to consider a complete oil change, and possibly looking into the spark plugs since this is the rough area of most heat production, is there anything else I should be looking for that I haven't covered here? I will likely change the coolant myself soon since I'm not 100% sure if it is the correct fluid which I know can cause issues, and it's a cheap enough fix compared to other alternatives within the engine itself. The front-most fan, visible through the radiator does not move, but I believe this to be for the AC (it seems to be linked to this system anyway), though the larger fan attached to the motor is running fine.

Secondly, the underside of the car looks rather like the insides of a cave (see image below). It is relatively well-stuck to the exterior of the car, but I can't say I've seen a lot of this from other cars that I've seen other people work on. The car has been between Sydney and Canberra in Australia in its lifetime, though now is with me in rural NSW. I'm thinking it could be as simple as dirt, perhaps mixed in with some oil, but wanted to check if this phenomena is common or if there's a particular way in which I should be trying to tackle it? This is taken just under the driver door, and this is mainly on floor panel materials as most functional metal under the car seems in pretty good condition.


Apologies if these are not particularly challenging questions, but thank you for your time in reading and helping!

 

The underside is normal. It's a body sound and rust proofing.

 

I see - thank you very much! It had occurred that it might be, but with it being covered in dust (and thus taking on the colour of it) I wasn't so sure.

 

Hi W,
I did not intend to be mean but since you invited, I had a little giggle since the spark plugs are literally at the top of the motor (sorry). OK, So you say metal part attached to the motor, Do you mean the shiny tin part on the right side? That is a heat shield covering the exhaust manifold so , Yes it will get almost as hot as the exhaust pipes which can be very hot especially with the catalytic converters immediately below in the engine bay. If thats what you mean , then dont touch that. (again, sorry) . Of the gauges, there is an oil Pressure gauge, and a coolant temperature gauge, If they are both centered when its running then you should be fine there. Changing the oil would be a good idea if you havent yet, but unless the oil is very old or dirty looking, I dont see that it will make the car "run better" in the immediate sense. Looking into the ignition system is a good idea, but I wouldnt just go throwing parts at it, that will only make you poorer. Spark plugs can be cheap enough, and you can check the plug wires for arcing (which means theyre bad) after dark or in a dark area inside. A look inside the distributor cap will tell if it or the rotor need replaced. You might also do a search of this section (the xj40 section) to find out about cleaning the intake system out which they need every so often too, and which I will suggest is likely the best way to improve the cars running. good luck, keep us posted.

 

The temperature gauge has nothing to do with the oil.
It is a coolant temperature gauge.
Is the battery in the engine bay or in the boot?
There are some differences between the two especially in electricals.

 

It was more of an indication as to which side I meant, although now you say that...yeah haha. That makes sense, though the engine itself is a little warm as well, but that does make me feel at least a little better. The temperature gauge never moves, it stays below cold, on the lowest white mark which is what made me believe it may not be great. The oil pressure does move and is optimal (for the small distance travelled). The oil seems clean and the former owner said that was one of the few things that they had done, so that makes sense. I believe it's running on all cylinders and it certainly idles, revs and moves fine. If the two items mentioned here seem to be normal - as they seem to be - then my next move will be changing the brake fluid and bleeding the brakes since it currently is either 0% or 100% brakes. Will check the calipers etc. also, getting a new battery since this one needs jump-starting every time despite looking relatively new (aware this could be caused by a drain however it seems to gain voltage over time, but immediately dies upon turning off the car). Transmission fluid seemed to have some bits in it so going to have to try and avoid running it around the paddocks too much until I can change that too. Thanks for your help, I'll take a look at the intake system also as that's something I'd only just realised to be pretty vital to check...I'm trying, I swear!

The battery is in the engine bay, since arrival it has been dead unless jump-started as stating above though runs fine otherwise, though need to test it when I'm doing more than just the engine I think, so may see the effect on voltage when I try and turn the AC on, which will likely just be another can of worms opened!

 

It does seem like a bad battery. If your temp gauge never reaches near the center of the gauge, you might try changing the thermostat, but first you can generally test the "actual" temp of the motor by turning the heater all the way to warm. if it doesnt make you sweat, then the thermostat may be stuck open. This condition will cause the motor to run a bit poorly, but not to be undriveable. Certainly have a look at those brakes. good going!

 

Thank you very much for the tip! I'll have a check of that for sure and report back! I've reached the second stage of do-er upper-ing; the "I wish I had more time and money!"

Excusing the poor image quality, the car itself is looking pretty fine!

 

So, finally got around to running the Jag again after a long week. Turned the heating on max and down to minimum and it was the same temperature so I’m assuming there’s a thermostat issue.

todays new issue is that the warm exhaust manifold is now sweltering on a much cooler day, as in 10 minutes after, the manifold and the 2 lines coming out were still creating air ripples from the heat they were giving out and producing a decent smell. I see that a broken thermostat can cause overheating and be caused by overheating which I suppose makes this a cyclic issue until I can get around to checking/changing the thermostat. I’ll look into it some more but so far seen it could be engine timing related or issues in the manifold itself. definitely going to wait to test the transmission whichever way, until I get this figured out. If you have any thoughts feel free to shoot them by me at great appreciation.

Just to mention: I am low on fuel (within the red) which could have something to do with it I've read. Just trying to work it out.

 

On the off chance I get a chance to work on the car tomorrow; any tips on checking timing? I’ve seen it done before on other vehicles, any videos I can find on the xj are…lacking in what “that” in a dark pit of despair refers to in my research.

 

Pretty sure the timing isn't adjustable on the AJ6 engine. The crank sensor and the toothed wheel on the crankshaft do the job and that relationship is fixed.

 

the timing is controlled by the engine control module in your car and cannot be adjusted. turning the distributor will not change the timing, however correct alignment of the distributor is needed to ensure a good transfer of the spark from rotor to distributor cap.

 

Thanks guys - going to have to hope that it's mainly the thermostat then. Bought a brake fluid kit today going to try and do that at some point coming up. I've been told there's a couple of different sizes of thermostat that are applicable to the car, in that they are a few mm difference, is there a way of measuring /finding out the size of the one currently in the car or does it not particularly have an affect and either would be fine?

 

Who have you been talking to? I suggest you take no further advice from them LOL!

You need to visit the parts catalog, get the part numbers for any parts you need and either order the part, google the part number or check out RockAuto.

Here is the parts catalog. You will need to know your VIN to use it effectively.

https://parts.jaguarlandroverclassic.../brand/jaguar/

 

Thanks! Repco, but they seemed confused by it being a Jag so I can’t say I’m shocked haha. Thank you kindly!

 

Looks like a 67mm is required from what I can tell then. Will check with the store tomorrow. Thank you so much!

 

I suggest you get in touch with Jagdaim in Melbourne for future parts.
They know Jag parts and over years of dealing with them I have been impressed with their knowledge and speedy despatch.
Unfortunately Repco has declined badly over the years and a once proud Australian manufacturing and distributing company is now just another parts retailer.

 

Thanks for the tip, will likely do that next time!

I assume that the picture below is the housing for the thermostat? Definitely a lot less cooling fluid after running hot last time and no apparent leak so I think it ate through a decent amount. Looking at the brake fluid reservoir also pictured below I’m thinking that this stuff probably hasn’t been changed in a while by how dark it is (and overfilled for whatever reason).

 

yes, that's the housing for the thermostat. You should have a 67mm diameter thermostat, for example a Gates TH14387G1

 

Thanks, I got a Tridon TT247-192 Also managed to snag some cheap injector cleaner to hopefully put to use soon!