Oh - so this would suggest that the SC radiator is not contributing to the engine coolant getting too hot?

 

Yes. If you look at the diagram I posted, you can follow the piping to get an idea of how each system's loops work. The major crossover point is at the big octopus hose seen at the outlet of both radiators, but I believe this is more for bleeding purposes as opposed to flow. They also connect at the expansion tank ('reservoir" in the diagram), but that is also for bleeding and overflow purposes.

Also the s/c produces a lot of heat under load, not so much at idle. So, if the s/c loop is not working correctly, the symptoms I would expect would be heat soak (reduced power after some spirited driving) and very hot intercoolers. This is easy to try, go and do some driving and high-power pulls, then stop somewhere soon after, doesn't have to be immediately but fairly soon. Give it a bit of gentle driving to let the intercoolers do their thing. If your intercoolers are too hot to touch after you stop then the s/c loop isn't cooling very well.

I don't believe that would cause the engine coolant temp to rise significantly at idle, especially in conjunction with a/c running.

 

+1

 

Thanks everyone for your input, I've now got to the point where it seems I can rule out:

• New Radiator
• New Waterpump
• New Thermostat
• Auxilary pump
• SC pump
• Replacement second-hand fan assembly
• Coolant loss

I wonder if the [authorised] Jaguar service centre would have any better luck trying to figure out what's going on?

 

Have you checked your coolant, radiator hoses? Sometimes an older softening hose could restrict the flow.

You may also want to have a test done on the coolant to make sure you do not have a cracked cyl. head or a blown head gasket.

 

Okay, so I thought I'd start a new thread on this as it may help anyone else that is having unusual problems, for reference, here's the original thread:
https://www.jaguarforums.com/forum/x...placed-174335/

After battling overheating issues with my XJR and almost giving up - I decided I'd make the big 1.5 hour trek from one side of Sydney to the other - I booked my car in with Dr Jag (https://www.parsonsmotors.com.au/)...

The last straw was returning from Summernats last year when it was 46*C and my car was overheating while at 100+ km/h on a motorway....but that's neither here nor there...

So...it seems that when my car fans had been checked prior they were both spinning. When the car hit 95*C the fans switched to the full-speed - a quick inspection would also show both fans spinning away.

But were they? When the fans are on half-speed they operate in series (a fused circuit) but when they switch to full-speed they go into parallel (each fan has a different circuit/fuse). One of these fuses had blown. So, within a few minutes of switching to full-speed one of the fans would gradually slow and stop. The engine would then begin to overheat.

Seems so simple...why was this so hard to resolve? I don't know how other mechanics missed it. It cost me a fortune in repairs...and the final result - a fuse worth a couple of bucks. A bitter-sweet victory :-)

Troy.

 

Wow, a frustrating experience, but pleased to hear that it is not only fixed, but that it turned out to be something simple.

 

So if the fuse blew is the fan motor pulling too many amp's ? In my experience a blown fuse tells you to look for the cause.

 

This saga began when something from the road ricocheted into the fan assembly, dislodging the frame and causing one the fans to jam - I suspect this is what may have blown the fuse too.

 

Very likely - the stall current (of an electric motor) is much bigger than when rotating.

 

Hi Troy,

Thank you for reporting your resolution of this issue. I have merged your new thread with your old thread so the full saga is all in one place for future readers.

Cheers,

Don

 

Just to be extra clear, is this fuse on the actual fan or is it with all the others in one of the fuse boxes?
​​​​

 

Wow ... this is a thread worth reading and not forgetting!

 

I believe it is the a fuse within the fuse box as the fan itself works when running in series.