the computer flashed 'check engine oil', as I have been unemployed, it had been a long time since last change (about 20k). I changed the oil & filter. The same message now comes up and oil level is not low, although about a quart over now... Today the oil light (idiot light) flickered while I was at a stop light; engne was running to the hot side (but not overheated). This car does have an oil cooler also. How "probable" is it that oil pump is bad?