XK8 Temp Gauge went up to red but engine not overheating

[davidt34]

Hi everyone
It didn't even occur to me that the part I ordered wasn't a Jag made part!. I just assumed that the British Parts guys sold original spares. My mechanic didn't fit the new temp sender in the end as he was sure an airlock was the problem.
I'll now order one from the local Jag dealer in Milton Keynes as I do want a new one fitted.
I'll keep the other one as a spare in the car.
Thanks again for more useful advice.
Dave

[J44EAG]

The V8 can be a bit tricky when it comes to burping air out of the coolant system.

When I`ve had the thermostat tower or water pump off for replacement, I found the best method was to refill to the top of the tower with coolant, then top up the header tank to the correct level, warm up the engine to operating temperature, release the header tank cap to expel further air, then crack off thermostat tower cap just to be certain all air is expelled at that point. The tower cap is the highest point on the engine so that is where any trapped air is likely to accumulate.

Given that you are reasonably certain that you have done a good burping job, road test the car, carefully relieve any built up air pressure within the header tank via the tank pressure cap and once again check the header tank fluid level. That should ensure all the air is out of the system and that an air lock does not exist. After that, all should be well.

Mike K

[davidt34]

Hi everyone
Ive noticed today that there is only one bleed hose attached to the header tank and that goes to the thermostat.
Is this right?.
Iooking online most pictures of the xk8 engine show another bleed hose going to a recovery tank.
Thanks again
Dave

[mike020150]

There should be 2 pipe stubs on the expansion tank. One links to the thermostat housing and the other is an air bleed to the radiator. Mike.

[davidt34]

Hi Mike
Thats what I thought but I looked closely this morning and one does have a bleed hose to the thermostat but the other stubb has no hole in it and is sealed off (the stub is just solid plastic).
Could this have been removed as part of a later modification or is it likely to have been bodged?.
I did a 160 mile round trip yesterday with some hard acceleration and also some queueing in traffic and this morning the level in the expansion tank is spot on with no drop in level.
The car is running beautifully so not sure what to do.
I even averaged 28 mpg which I was deilighted with.
These are truly great cars and I am already truly smitten with mine.
Thanks
Dave

[doug424]

Hello Dave,
I have a 1998 XK8 with one pipe from the expansion tank.
I think you should not worry as in my 10 years of ownership the only attention I have made to the cooling system is a new thermostat tower.

Doug Barrass,
Ashford Kent.

[davidt34]

Hi Doug
Many thanks thats very reassuring!.
I've seen a few pictures of xk8 engines on the web that show one bleeder pipe and some that show two.
Best regards
Dave

[oyster]

Hi.
There is a difference from -97 to -98. VIN 001001 to 018107 got two bleed pipes. VIN 018108 and on got only one. TSB 303-15.

[davidt34]

Hi Oyster
Many thanks that is just what I hoped to discover.
The diagram is really useful and mine is set up as per the later my1998 diagram.
Best regards
Dave

[oyster]

Hi.

You can find the complete TSB 303-15 at http://www.jagrepair.com. Lots of other useful information as well.

Rgs

[mike020150]

Thanks everyone, especially Oyster. Off the top of my head, I couldn't quite recall whether there had have been a single pipe version so before I responded I checked Jaguar's Topix system which only mentioned the two pipe version. Hence, there's a lesson to be learned. Topix doesn't necessarily contain each and every variation! Mike.

[oldtimer]

Another food for thought,
Once again back in ancient times. Radiators returned under Waranty which had been fitted to a particular vehicle who's name will remain nameless, (not Jaguar) suffered badly as a result of failing to fully bleed air from the cooling system. This caused super heated steam to be generated which in turn blew the plastic header tank away from the radiator core. Examination of the attachment of the header tank to core will reveal turned over fingers that secure the tank. Between the two parts is a rubber sealing gasket. Sudden excess pressure damages this joint.

What ever method of system bleeding is used be confident that it is free from air.

Rgards Oldtimer