The heat shield on mine had the Torx bolts, but it looks like your has normal hex head bolts--they are the bolts & that is the heat shield

I fully removed the coolant expansion tank on mine as it made access easier-the connecting hoses could then be pushed out of the way.

I considered doing the job from underneath, but I couldn't see a way as the heat shield is still in place.

You can do it from the top but it can be fiddly as there are several hoses in the way which need to either be removed or pushed out of the way, so you can get the heat shield off & pulled up.

So yes, remove those hex head bolts & carefully wriggle the heat shield up-it is easier if you remove the coolant expansion tank as you've got more access room then.

Persevere, because it can be done & it will eventually come out-it's not a quick job though if you've never done it before. Hence my suggestion to allow a morning to do the job if it's your first time.

The heat shield is very rigid, so you can't bend it to get it out-you have to move the other softer hoses out of the way first, or you'll chafe the hoses with the sharp edge of the heat shield & have a coolant leak when everything's re-assembled...

 

Looking at your throttle it's an AJ26. Also agree that removal of the header in this case may be better by the sound of it.
To do this you need 2 fine tipped flat screwdrivers to remove the hose clips from the tank. You put one driver down each side of the clip bands, the aim is to spread these out and wiggle the hose free. They also break easily so go slow and steady.
Once it's out of the way, an extension or 2 and an 8mm socket will get the heat shield out.
Then onto the sensor, have you managed to unplug it yet as the link lead needs to be free to remove it.
Good luck

 

I used a small pair of mole grips on the hose clamp, although it was a bit of a fiddle & only works if the tangs are facing an area with enough space to get the grips on

 

As far as unplugging the sensor goes, I haven't yet located the plug in point for it. I intended to follow the cable back from the sensor to locate it.

 

The sensor plugs all sit in the same bracket above the flywheel bellhousing-you'll need to remove the Evap valve, then unscrew the securing nut that holds the engine electrical plug/harness assembly in place-then move it out the way, but don't disconnect it. You'll probably skin a knuckle or 2 with this job.

It's called 'bonding' with your car

 

Thanks for all the help guys. sensor is now changed, just need to put back the heat shield and coolant reservoir then make sure everything works.

I can safely describe changing this sensor as the most difficult mthing I have ever done purely due to the heavily restricted access. I guess jaguar never thought about how you would change these when they designed the engine bay.

 

well done, out of the 4 it's the trickiest.

 

Well done & I know it's not the easiest of jobs-keep an eye on the coolant level for the next day or so as when the airlocks bleed out the coolant level will drop & may give you the low coolant warning.

I suspect Jaguar may have hoped that the job was so hard you'd take it to the dealer & pay them to do it

 

Well thats everything back in finally. Getting a bit of smoke from the area I was working in but nothing obvious burning. Hoping its just a bit of spilt coolant burning off. Time to take it for a test run.

 

Took the cat for a test run (about 30 miles) with no issues.

OBD gives a trim level of 0.78% instead of over 14% so looks like problem solved although will need the gas analyzer to check.

The big difference I have already noticed is in fuel economy. Prior to replacing the sensor I could never get better than 16 MPG (avg from the cars computer) tonight I averaged over 23 mpg (using the cars computer) if these figures are even remotely correct I shudder to think how much I have spent on fuel due to a bad sensor.

Thanks to everyone for their help and advice, this has got to be the best car forum going.

 

Good result there & that's a big improvement in fuel economy-now you can get out there for a proper long drive & enjoy those extra 'free' 7 miles per gallon

When the O2 sensor fails, the ECU defaults to a base fuelling map which usually results in higher fuel consumption as it can't 'trim' the mixture to the ideal level for the driving conditions.

Anyway-nice work & the sensor replacement cost will soon be recouped in the better fuel economy...

 

tberry, I'll keep my fingers crossed for you that your car will pass the MOT now. Please keep us informed.

 

Well done, I've marked the thread 'Resolved' but please post the MoT result - which will be OK !

 

MOT booked for wednesday as it needs a new brake pipe and the passenger side handbrake needs a clean up. Will let you all know how it goes.

 

tberry:
Assuming I have not lost my mind (possible!), the coolant lines on your tank in the picture in post #40 are reversed. The top line goes to the resevoir in the wheel well. Yes, they should cross!
Your cooling system will not pressurize as connected.

 

Should the pipes cross ?

Connections to the coolant system have been this way since I got the car.

My XK-8 should (probably)have the same layout so will check later.

 

Just checked my own XJR & the coolant pipes do indeed cross on mine as well...

 

Interesting post, my car to has always suffered with poor MPG and emission test failures, though I recently found out my exhaust had 8 holes in it so I have replaced this and hopefully this should solve my problems, Im now waiting for my MOT on the 19th Feb to find out.

However if it doesnt then Ive got a feeling it may be an upstream or downstream O2 senor.

I have been told my left bank is running slighty lean, I have had my ECU fault read at a garage and no fault codes came up, however he did mention there was a small change in volts on one of my O2 senors, but in his opion this would not cause high emissions or poor MPG and was likely to be my exhaust.
If an O2 senor had failed would he be able to see this on his ECU reader?

Would some-one UK based on the forum be kind enough to lend me their OBD reader so I can measure my feul trim levels, Im happy to pay for postage both ways and will return after a couple of days.

 

You can buy one for the cost of SD postage...

you got bluetooth on your phone?

Wireless Car ELM327 OBD2 OBDII Bluetooth Diagnostic Interface Android CAN BUS PC | eBay

get Torque app...
Torque — OBD2 Performance and Diagnostics for your Vehicle

And a whole new understanding of your car...

With a little help from this forum.

Hope this helps

 

Finally managed to get the car tested today.

Emissions results

Original test Todays test
FI
CO 1.6% 0.00%
HC 73ppm 15ppm
Lambda 0.96 1.00

NI
CO 1.41% 0.00%

Don't think I could have hoped for a better result.

Car now feels much more responsive and fuel economy is about 30% better than before.

Thanks for all the help guys.