Help re. Low cylinder compression

[tvrheart]

Following a new head gasket my BMW hasn't ran completely right. Before I take it to the garage next week for an MoT and investigation into this problem I thought I'd arm myself with some knowledge. I did a cylinder compression check today, all bar one of the cylinders read around 11 bar, with number 4 reading about 8.5. The car is a 1989 BMW 325i Touring with 152k miles, it also needs regular topping up with coolant. Any ideas on what my problem may be, and an idea of how many £££s?

Is now the time to sell it?!

Thanks for your help,

Chris

[tvrheart]

The head was skimmed. The oil looks fine with no cloudy or milky effect on the dipstick or filler cap. The spark plug looked the same as the others too. This is why it is so strange as it is using coolant, but doesn't appear to be entering the engine. Someone said it could be to be do with the valve clearances but again this is where my understanding ends!