Headgasket blown between 3 and 4 cylinder - remove plug and inspect crown of piston through plug hole - If its 'washed' - clean (ie no carbon deposits) it means your head gasket has gone !!!!

my anti freeze is the fluorescent yellow type, but i can fing any leaks!

yes it could be a duff plug, you may just have a water leak mate..
what colour is your antifreeze, as it will be visible around a leak :)

recently ive been loosing water from the cooling system at a slow rate, and therefore thought my head gasket was leaking water into the cylinder overnight, due to the fact that the engine tends to misfire for a few seconds from cold start up (burning off the water methinks) and also bubbles can be heard in the cooling system. after doing a compression test i discovered that all the cylinders held a pressure of around 15 bar, so i abandoned the theory that the gasket was leaking.
altho the ceramic part of the spark plug (not the electrode) from the 4th cylinder was a rusty brown colour, whereas the others were perfect. (they were changed around 5k ago. (35k on clock now)
there is definately no water in the oil.
no water leaks inside the car
all hoses are intact

what could be happening in this cylinder?


i have topped up the header and ran the engine with the cap off until i could see no bubbles, this seems to have stopped the gargling

also i have put a new plug in the 4th cylinder to check in a few days to see if the same thing happens to it
there is no engine warning light as the ecu isnt involved
car is still misfiring in mornings even with the plugs swapped around. could it be a duff plug?, but then that doesnt explain the water loss.

sorry for the essay, anyone got any ideas?