Hello!

I just got back from Monterey Car Week where my XJ12, despite some reminaing foibles, performed very well! I put nearly 300 miles on it and it did nothing but be a comfortable and reliable V12 phone charger. I'm starting to plan next year's car week and would very much like to drive the XJ rather than trailer it up. Therefore, I'm compiling my list of parts I need in order to fully rebuild the suspension and shore up the dam of fluid leaks. That being said, I get a bad case of "while we're in there" and would like to replace some stuff preventatively. I'd like to get the general groups consesus of a few items I'm looking at replacing preventatively:

1. Water Pump. While I have the front subframe out to do the sandwich plate, power steering lines, V-mounts, etc, I also want to replace all the coolant hoses as they are 27 years old. On most other cars this age people generally replace the water pump as a maintenance item. I understand it's not available anymore, but JagBits does offer a rebuild service. The reason I'm considering is a friend with an XJ40 at car week had his water pump basically blow up. Would this be a pertinent job to do or do these 6.0L water pumps generally last the course?
2. Thermostats: Mine are operating fine at the moment, but they seem fairly inexpensive and it would be nice to not have one fail shut in the middle of the desert.
3. Harmonic Balancer: At the moment, my car does not show any symptoms of a bad Harmonic Balancer, but it appears it can be a problem. Would it be a good idea to send it out for a rebuild preventatively or just leave well enough alone in this case?

 

The problem with the harmonic balancer is if it completely fails to turn the water pump belt you have a major overheat issue way out somewhere , and the expense and hassle

But it may give you alternator issues before you get to a overheat

 

This is going to be a long thread but to kick things off I think it's helpful to divide the car into above and below, particularly the engine.

There are lots of areas made accessible with the front subframe removed, which I think it's best to tackle first, then move on to the 'above' jobs; oooling and fuel hoses etc.

in haste

 

That's exactly why I wanted to ask! So far I've done everything but the cooling hoses from the top (Injectors, cross pipes, everything ignition related, map sensors, IACs, valve cover gaskets, vacuum hoses, etc.) so I'm now prepping to go below deck. So far I'm planning to do the oil pan gaskets, have the differential resealed, and while I have the front and rear subframes out of the car, I'll take the opportunity to replace every rubber component in the suspension.

The reason I asked about these items is I want to make sure I mitigate any source for potential failure in the future and I need to do the drive belts anyway. They're pricy and I haven't heard much in the way of extreme failures, but I wanted to hear any and all opinions about having those done for the sake of ongoing reliability.

 

With the subframe out ( you will need a harborfreight engine support bar and self fabricated engine mount hooks) you can access and replace the oil cooler lines, the two sump gaskets, the o rings for the oil pump pickup and out to the filter housing (this seals up any oil pressure leakage back into the sump), the alternator is right there and easy to access. The steering rack will be out for inspection along with the ability to replace any suspect power steering lines. The lower radiator hoses is easier to work on while the subframe is out. The trickiest issue is the pneumatic motor mounts which are unobtaininium, very expensive if you can find them and the old ones are very fragile.

Take huge numbers of before pictures particularly detail so you can get it all back together in order.

I must have removed pounds of oily crud and now have a very intimate knowledge of the radiator, underside and suspension of mine now. I had previously replaced some of my upper cooling lines but am just now starting on going through the top of the engine, cleaning inspecting, replacing etc.

The suspension is standard x300, and you need to fabricate the spring tool to remove and recompress the springs. I used powerflex urethane bushings at front, bilsteins, lemforder ball joints etc.
I haven't done the rear yet but have bilsteins waiting to go in and will inspect all bushings.




Pictures here because it can seem very overwhelming but once you clean and paint stuff it all gets demystified.

 

A source to have the lines terminology is here

Search Genuine Engine Cooling System Parts For Jaguar Xj 1995 - 1997 (from 720125 To 812255) Classic | Jaguar Land Rover Classic Parts

and for oil system

Genuine Oil Cooler And Pipes-6.0 Litre (6.0 Litre) For Jaguar Xj 1995 - 1997 (from 720125 To 812255) Classic | Jaguar Land Rover Classic Parts

There may be a hose circuit path diagram somewhere for reassembly or at least a functional diagram

The engine coolant refill procedure is critical

There is a document someone made to calibrate the 2 thermostats before installation as they can be way out of calibration as a new part off the shelf

 

see page 67 ( which covers the V12 ) and 50 for the oil

Notice there was a change in the coolant type and they do not mix

there are cheaper generic brands

 

I'm familiar with the coolant procedure. I have all the dealer service manuals and have followed them to a T. I replaced the coolant when I first bought the car (Hadn't been changed in at least 7 years...), It was pretty simple from what I remember.

Now Thermostat calibration? Thats a thing? How does one do that? I've never heard of a thermostat what wasn't ready set, immediately out of the box...

 

The thermostat calibration has to do with the small margin of a correctly operating temp ( for the V12 ) and an expensive overheat

This is a problem from reading other's post , I do not have a V12

 

The calibration Doc is on another computer and has to do with measuring the opening gap ( micrometer ) referencing a climbing temp water submersion bath in a pot

 

Points 1 2 and 3 are must-do's. Really there are a lot of must-do's over the whole car. One thing to be aware of is what brands of parts are you going to use? Jag's can be super expensive, Aftermarkets can be super flimsy. Uro rubber is not advised for heavy suspension parts, and Powerflex products are notorious for bad fit. And anything bought over the counter at the auto parts store... ? Its a lot to consider.

 

Alrighty! That answers my question on 1 & 2!

Believe me, I will buy OEM Jagaur for everything I can (and have been doing so far with this car actually). My general principle is if its not in an OEM box or from the OE provider, it dosent belong on my car.

 

I'd say number one on your hit parade is replacing the oil cooler lines. Hot oil leaving the sump via the oil pump and into the lines are like opening an oil vein when they fail - you are essentially pumping oil out of the sump all over the bottom of the car and road. Because the line is so close to the down pipe and cat you will see smoke in your rear view mirror when this happens.

They always seem to fail at the top end at the hottest point



Once the subframe is out and you've cleaned up the repair is pretty simple, carefully cut off the seals with a Dremel



Buy some good quality replacement hose and use a heat gun to soften the ends to install on the barbs, using good quality hose clamps and/or 2 ear clamps. I took the entire oil cooler off and installed hose onto the barbs in situ rather than removing the speed fittings which sometimes fail when you try to reattach and weren't leaking.



You can use the old hose as a guide for cutting the new hose but the longer one will need to be cut and installed on the car to get a neat fit as it is less flexible than the old lighter hose.