My 2003 1.4 fiesta has been sitting for about 6 months without being driven. I run it every few weeks. I don't know if the headgasket is blown, the oil cap is sometimes milky (nothing terrible) and there is gasses escaping from the coolant reservoir cap. I ran it two days ago for about 15 minutes and now the oil cap is white, not sludgy just more white than usual.. Also I ran it a few months back and the coolant cap blew off and coolant went everywhere.. Is this two seperate issues or just the headasket? I've read that if you don't run it for a long time the oil doesn't get hot enough to evaporate the water, so that could be why; and that the reservoir cap has a valve that could be broken and not letting of enough gasses. Any ideas would be appreciated.

In the two GIFs i have uploaded shows the oil cap and the coolant cap bubbling (the level is also way above the max mark)

EDIT: I must add that the radiator fan only comes on after the engine is switched off (not at all while it is on).. is this a problem aswell?

the only reason the reservour cap should start releasing pressure is if the coolant system gets to an overpressurised state (usually if the car was overheating) in terms of the milky oil on the cap that is normal on a car that has been sitting for 6 months as you get a tiny bit of atmospheric air inside the engine and then you will have some water condense on the cap

1 minute ago, Neb_engineer said:

the only reason the reservour cap should start releasing pressure is if the coolant system gets to an overpressurised state (usually if the car was overheating)

This usually starts releasing gas after like 5-10 minutes of idle.. The temp gauge on the dash takes about 15 minutes to get to halfway so how would it be overheating? 

make sure the cap is on tight, otherwise you have a faulty cap

2 minutes ago, Neb_engineer said:

make sure the cap is on tight, otherwise you have a faulty cap

The cap is on tight. that is the first thing i thought. Must be the mechanism inside the cap, that was my next guess.

Just now, CollumPlz said:

The cap is on tight. that is the first thing i thought. Must be the mechanism inside the cap, that was my next guess.

yep, if the cap is bypassing at a lower pressure than it was designed, you need to replace it, part of the reason the cooling system in a car doesn't boil is because the whole system is under pressure (until the pressure gets too high do to an overheating engine and the cap bipasses to avoid an explosion), on older vehicles that had radiator caps, they would have an overflow tank when the cap bypassed, on a ford, the coolant just goes all over the engine bay when the cap is bypassed. these resevour caps do have a finite lifespan due to how they work and the high/ low pressure cycles

14 minutes ago, Neb_engineer said:

yep, if the cap is bypassing at a lower pressure than it was designed, you need to replace it, part of the reason the cooling system in a car doesn't boil is because the whole system is under pressure (until the pressure gets too high do to an overheating engine and the cap bipasses to avoid an explosion), on older vehicles that had radiator caps, they would have an overflow tank when the cap bypassed, on a ford, the coolant just goes all over the engine bay when the cap is bypassed. these resevour caps do have a finite lifespan due to how they work and the high/ low pressure cycles

I'll order a new cap and see if that works then. Thank you.