Saddle valves, also known as tee valves, are useful to easily supply water to small appliances
No they would come under "G" for garbage
Yes, you remove the rockers, add air pressure in the cylinder through the plug hole and use a valve spring compressor to remove valve spring. You can now change the valve seal.
If there is only one plug, try removing the plug, spraying WD40 in the plug hole, replace the plug and try starting.
If you mean the hole behind the camshaft between the valve cover & the head, then you remove the valve cover, install a new plug & valve cover gasket, and reinstall the valve cover. The part number for the plug is 1336763.
Apparently yes! By either threading a comprsor hose down the spark plug hole after removing the spark plug it or filling the cylinder bore up with 6mm nylon rope to prevent the valve from dropping.
if the oil is at the spark plug base the valve cover gasket is leaking. if the spark plug electrode is covered with oil the engine needs rings
Search leak down testers.
Failed seal under the valve cover on top of the plug tube.
there is only a fill plug on this differential. The only 2 ways of removing the fluid is by removing the 10 bolts that hold on the diff. cover, or a hand pump that can suction the fluid out through the fill plug hole.
Bad plug, or plug wire, burnt valve, blown head gasket, hole in piston, defective coil on plug if equipped.
it could be the exhaust valve oil seal wants replacing! blue smoke means oil is comming down the valve stem and going into the exhaust: black smoke is where oil is beening burnt in the cylinders i valve stem seals are a common problem on 205 gti's. most likely that. remember you can replace stem seals without removing the head by feeding string into the bore throigh the spark plug hole, turning the engine (BY HAND!!!) to comress the string against the valve and then removing the valve spring as normal. saves loads of time and countless hundred pounds! just remember to keep the end of the string dangling out the plug hole otherwise its a real sod to get out!!!
Through the spark plug hole, soak the valve with penetrating oil. After sitting a while, tap lightly on the valve stem with a hammer. If after several tries this does not work then the head will need to be removed to see why the valve is stuck.