Went on searching for my next V car and looked at 40,000 miles V50 at the dealer. Engine started right away, no strange noises as far as I could hear. Oil cap had mayo/ mustard looking stuff inside. Dipstick oil looks dirty but clear, I know that dealer recently changed it. Car runed and idled OK, but coming back after spirited run coolant was constantly going back to return reservoir at idle. It also looked strangely clean and blue and almost too new for the milage. I walked away from the deal, although I liked the car overall. Do you think I should come back or this car is trouble-in-waiting? Please, advice.
Mike:

 

They all have that on the cap, it's condensation.

 

Can you please explain that. I've never seen this happening on any of my cars and cannot find this with internet search. It would be an expensive gess to make. Also, how can you explain fluid running back to expantion reservoir?
Thank you again for you patience. I just do not want to buy a project car.
Mike

 

I see it all the time. Go check out another P1 Volvo and check the cap.

I don't know why it builds up there, it just does.

Have the shop check for exhaust gas in the coolant reservoir before buying if you're worried.

 

That what i thought. On my way to autozone to rent the tool. How about coolant? Do you see it runs back to reservoir while the car idles?
Thank you for your continuous support. Mike

 

Yeah, that's what the reservoir is for. If it was bubbling, that would be cause for concern.