The valve cover ask it, on a S 40 Volvo, can be replaced by first removing the valve cover. Remove the old gasket and replace with a new gasket.
First check to see if the valve for the water supply is turned on. If that isn't the problem you may need to replace the tank water valve, they do wear out and are not that expensive or difficult to replace.
You need to clean (or replace - $200) the idle air valve.
It's better to go ahead and replace it.
About $115. Labor $75 and valve $35. It takes about an hour. Most cars.
The PCV valve on a 2004 Volvo S40 is located on the engine crankcase. It is a small rubber valve.
Valve clearance of Volvo f12, are set using a feeler gauge on the lash adjuster.
Get a mechanic to do it. You obviously have no idea as to the complexity of the task. e.g valve stem seals, valve seats, warped head tolerances etc.
When facing the engine, you'll notice two small fittings on either end of the valve cover. The PCV valve is the one on your left. Unscrew the plasic cap and replace the valve.
For valve clearance of Volvo d13a one needs to remove and re install injector cups.
Oil starts to leak from the gasket. Generally it doesn't pose a problem to the engine unless you run it out of oil. It does make a mess, however, and they're not that expensive or difficult to replace.
I'm Trying To Change The EGR valve ON My 1999 Nissan Quest How Difficult Is It Going To Be, Please Help