[Sundayjumper]

Yes, I failed my due diligence, yes, it was cheap, yes, I've possibly made an expensive mistake 🤣 It broke down on the way home from collecting it. It managed 35 miles of a 90 mile journey.

But it looks nice. I like the anonymity; it could almost be 520d unless you knew.

November 2013 LCI with 120k miles and apparently FSH.

It is showing what I so far believe to be classic valve stem seal failure. Runs & drives OK but guzzles oil. Left idling it gradually starts to emit smoke from the exhaust and then when you take off there's a huge cloud of it. Doesn't smoke on startup (which would be injectors ?) or when moving and suddenly hoofing it (turbos, rings ?). It had 8x new coils just before I bought it. I've already done the 2x breather hoses. I have 8x spark plugs ready to go in. I'll do compression & leakdown tests first though to hopefully eliminate the nightmare scenarios. I've not had an F10 M5 before so to be sure I wanted to check:

Compression. Is this the same as any other car - remove fuel pump fuse, remove all spark plugs, spin the starter for a second or two ? Will the car throw a wobbly when it doesn't start after a couple of tries ?

Leakdown. Must it be done at TDC ? Anywhere on the compression stroke would work, I think ? Is there a smart way to determine TDC or do you just stick a screwdriver down the open spark plug hole and turn it (slowly, clockwise) with a bar on the end of the crank ? Turn it 90° and move to the next cylinder in the firing sequence ?

The tools are on the way to do this in the next few days.

If that all checks out I think we're onto the valve seals. Have any of you guys done this job:

* DIY
* With the engine in the car
* Without using the $$$$$$$$$$$ AGA toolkit

I'll pull the engine to do it if I have to. It looks dead simple once the engine is out.

FWIW I'd call myself an experienced DIYer, I'm not afraid of a spanner. I'm well kitted with tools & stuff and I do all my own work on my 360, but that's quite crude tbh. The F10 is super high-tech by comparison !