Finally got Amy in the car to have a listen, since my hearing is pretty useless really.
She said "Sounds more like the fan with a leaf stuck in to to me, rather than a metallic noise". Somewhat reassuring.
Did about an hour and a quarters drive with it yesterday, noise still there but nothing like what it was when it first happened. Turned onto a nice long clear straight and let it run up close to the redline and it pulls along just fine.
In the meantime a new toy turned up:
More tools are always good, especially when they have flashing lights on them.
Although when I removed the distributor, I made sure I put it back in exactly the same place, I'm relying on whoever else had it off in the past doing the same. Since it was up to operating temperature after our little run, I decided to have a play.
Operator error at first had me thinking it was faulty when the inductive tacho part said it was doing 2,410rpm at idle. I then noticed there is an arrow on the pickup that has to point towards the plug. Interesting that this makes a difference.
Once it was hooked up correctly, I wound the hot idle down to 900rpm (you may remember I have it set to around 1100 in P so its comfortable when in D), removed the vacuum line to the ECU and pointed at the crank pulley.
It's as close to 12deg BTDC as it can be given the accuracy of the markings on the timing cover, which is good news. Advance seems to function too.
So thats that off the list of things to do/check for now.
While I was doing this, I spotted this little electical gizmo that I hadn't really acknowledged up till now, and I don't recall seeing on my previous cars:
Now to me, that looks like a solenoid valve attached to the idle speed air circuit. I suspect for idle speed compensation when engaging drive. If that is what it is, it clearly doesn't work but it would be very good to fix.
Starting point I guess would be to undo the allen bolts and remove the whole assembly and drench in carb cleaner.
Anyone know if there is a gasket, or an 'o ring' behind it?
I had another play with the endoscope too. This is the underneath of No3 manifold-head joint.
Its hard to get in focus, but I reckon that is soot?
I'm not touching it until the XC is through its MOT just in case it all goes wrong...
I've got a set of Elring gaskets, I've ordered some new copper flashed nuts, and also a full set of Volvo studs (actually ordered them from the Volvo penta website as they came up cheapest that way)
I'l replace the nuts as a matter of course, but if the studs are ok once the manifold is off and clean up alright I won't risk snapping one in the head for the sake of it and the new ones can go in the spares box. Fingers crossed.
I really hope that is it.
Before then, I've got a 50 motorway miles to do in the week. I'll take it steady and she'll chug on!