Inconclusive investigation work today.
22/23/24th Jan were very busy and I did about 350miles in those three days. All was going well, until on the way home on the 24th I was heading up the slope of the bridge at Avonmouth at 70mph when suddenly the engine/exhaust note changed accompanied with a loud 'click click click click click' noise that sped up and slowed down with the engine.
I'm not sure if it lost any power, I think I just instinctively lifted off and the hill slowed me down.
Of course based on the history my first thought was that something that got clobbered when the belt stripped, had finally given up.
I got into Gordano services, left the engine running and popped the bonnet. It was still clicking away loudly and sounded like top end.
On the basis that it was still running, still had oil and coolant in it and didn't have a visible hole in the block, I decided 'F*** it, lets get her done' and ventured back onto the motorway and did the next 30 miles at 55 with it clacking away like a good 'un.
I was planning on taking a video when I got home, but when I got home after the few miles of driving off the motorway it didn't sound too bad?
The car was then used for about another 70 miles of school runs. Drives fine. The sound is still there all this time, hwever much quieter than when it first occurred, mostly noticeable between 1,500 to 2,500 rpm under load, seems to disappear off throttle now, and is heard mostly when warm.
A dose of the flu since last Thursday meant that I spent all last weekend in bed and was unable to investigate any further until today, and I still feel a bit pathetic!
I pulled off all the belts and checked for noisy pulleys. all good. There is the *slightest* bit of play in the water pump pulley if you grab hold and properly yank it around but nothing to worry about.
Checked the timing marks, all good.
Also means I could listen for things without the fan noise.
While it was cold, I got Mrs1Roll to (attempt to) hold her hand over the exhaust while I felt round the manifold joints - I couldn't feel anything in the 15 seconds it took to start getting hot enough to burn me.
Tried listening around with the length of heater hose in the picture - couldn't find anything.
Moved onto a compression test:
Those results are [checks notes]
better than when I got the car, presumably from being driven regularly.
I was originally thinking about whipping the valve cover off, but with those compression figures I think I'd be wasting my time. if it was a valve/spring/ something that had given up I'd have a low cylinder and/or a dead miss, surely?
So, in conclusion, I have no bloody idea where this noise is coming from!
I've ordered a set of Elring exhaust manifold gaskets, maybe I'll fit them and see. Manifold studs don't look too bad, a dose of ATF an acetone should hopefully get them off. I hope.
I can't see any soot deposits (especially with the oil from the rocker cover which is leaking again!) or feel anything at idle when cold but all the gaskets look like this:
So I gave up and washed it!