1.7 CDTI, Astra, 25000 miles, Car makes squeaking noise for 1-5 seconds straight after start, depending on the temperature it was sat overnight in the cold which is below freezing temperature and then noise is completely gone. Took to garage for yearly service, they changed the glow plug and left it overnight to see the problem occures, the next morning(the weather was mild) it was completely OK. Now after few weeks the problem is back(the weather has been cold). I'm completely novice when it comes to engine anatomy. Still I suspect, its has to do with the temperature. Help please.
I'm with R. I believe it's probably a slipping belt. Some cars are notorious for that if the exact OEM belt isn't used. My Mitsubishi is one of those. Off the shelf (even high end, "guaranteed not to slip" type) belts from parts stores like to slip and squeal even when tightened to spec. OEM works fine...
That said, I did once have a very similar squealing sound on start and it was the engine oil pump starting to fail. A few months later it seized up.