So today I finally decided to start tackling this. Car has been sitting since last I wrote anything here. Decided to start by disconnecting coolant hoses from the turbo. Noticed that there was no standing coolant in the first hose I disconnected. I expect there to be standing water here as it is at least slightly below the Min level in the expansion tank.
As you may be aware, it's more or less impossible to tell the coolant level from the indicators on the tank, it's just too opaque. Anyway, turns out I could pour about 0.8 litres of coolant in to it before it reached the min level.. After filling it up, I put the heat shield back over the exhaust manifold, let it idle for a while with the cap off the expansion tank just in case there was air in the system. Level seemed OK.
I take the car out for a test drive, giving it all up the hills I have available. No issues. Fine, I hook the caravan up (which is mine now btw, I bought it rather than returning it..). And go out again. I've been going back and forth up the hills for a total of about 50 kilometres, every time slowing down before the hill and giving it absolutely all of the beans all the way up.
I just can't get it to act up now. The hills are long enough that I spend close to a minute above 4k rpm in third gear, foot completely to the floor. This is a good a test as I can get. When it acted up for real, it was always after at least 2 hours of driving, but that's not quite reasonable to recreate.
Here's a video of it, yes the CEL is on, but there're no codes in it and all performance is there. The CEL likes to come on every now and then with the caravan attached, always when the caravan is articulating a lot or going over bumps, I reckon it's some electrical gremlin in the plug or cable.
You reckon it could have anything to do with low coolant? Or I havent stressed it enough with this test? As I stated previously, moving the VNT actuatuor by hand it feels smooth and free, not catching on anything.
