A4 2.0 tdi 170 s-line 2007

[Dobe04]

Only had the car since October and it's costing me! Already had a new egr valve and dpf clean.
Latest problem.....
2 weeks ago parked the car, came back to it around 2hrs later, engine turned a couple of times then nothing except a whine of, i presume the starter.
No matter how many times you try, it turns almost to the point of firing then goes flat with the same whine.
Called the breakdown service, Sod's law 10 mins before they arrived it started.
Breakdown guy on listening to my explanation thought starter problem, I had the starter changed.
Then last Friday left the car, came back 15 mins later, exactly the same problem!
This time the guy that fitted the starter came out and listened to it, he was puzzled.
Tried starting....nope!
Tried bumping..nope!
Taken on a transporter back to the garage, by the time it got there 30mins (ish) it was starting again and has done since.
I'm at a loss, as were they when they put diagnostics on it....showing no faults!
Anyone encountered this problem or have a good idea what it may be?
It's now on 106k FSH
All help gratefully received, especially if it doesn't cost me a fortune. 😞

[Gazwould]

You have even more spending to do , oil pump drive , they don't make them like they used to..

[Dobe04]

Thanks mate, that sounds expensive!

[Gazwould]

Not too bad .

Expensive only when it fails as turbo and engine can perish .