OK folks, my first time doing a guide. The Briskoda community has provided me a load of help over the years, so I thought I'd give something back.
The crank case one way breather valve attaches to the crank case at the upper right hand side of the engine. It connects to a rubber pipe which runs to the underside of, and connects to the air intake hose. From what I understand, its purpose is to provide ventilation to the crank case to remove unwanted gasses which can build up. The valve is one way to stop air returning up the air intake and possibly into the cabin via the engine bay.
The tell tale for failure seems to be an oily smell working its way into the cabin (due to the one way valve not being one way any more), or oily fumes from the car while running. Checking the engine bay, you're looking to inspect below the throttle valve cover pressure pipe (the black pipe to the right of the plastic 'TSI' engine cover), near the front. You'll know if its gone as the valev will be broken and there will be a misting of engine oil surrounding the area.
The new valve can be ordered from Skoda direct or via Ebay - search for 'Skoda 1.2 TSI breather valve' and plenty of listings will appear.
To fit:
you'll need a Torx T30 bit, flat head screwdriver, a jug for some boiling water and some rags to tidy up mess.
Start by using your T30 bit to remove the two screws at the bottom of the black pressure pipe.
The black cover, which the torx screws hold down, lifts off once the screws are removed. Keep the screws safe.
Remove the electric plug at the rear of the pressure pipe, along with the wire to the left of it which should be clipped onto the pressure pipe. The rubber breather hose at the front right of the pipe should also be removed. There is a sneaky wee plastic black pipe on the underside of the pressure pipe as well, this should slide out downwards.
Once those parts are all removed from the pressure pipe, you are looking for two clips at either side of the pipe, at the very top, below where you removed the plug. Move them both out to the side, away from the pipe and pull the pressure pipe upwards - it takes a bit of force.
Once it comes off, pull the pipe out from the other end (at the turbo).
You can see where the oil has sprayed out from the crank case and onto the underside of the pressure pipe, as well as around the top of the engine. This is how the oily smell emanates from the engine bay as earlier described. Use your rags/cloths to clean it up.
Now you can get a closer look at the offending breather valve - or whats left of it.
The rubber grommet that the valve fits into (or did, before it broke) is needing removed. Use your flat head screwdriver, or other blunt, pointy object, to remove the grommet. The reason for removal of the grommet is to (hopefully) remove the remnants of the old valve. I don't suggest just pushing the new valve into the grommet without removing the old bits. If there are bits left in it, it is best to not push it into the engine where they are not meant to be. Check inside the crank case hole to see if any bit linger which can be fished out.
As you can see, some gibblets of the old one remained in my grommet, the rest must have been swallowed up by the engine- ho hum!
Clean out the grommet as best as you can with rags and then dump into your jug/cup of boiling or very hot water - it helps soften it up for putting back in place later.
The valve itself is a straight pull off of the rubber connecting pipe - just a friction fit. So pull it out of the pipe and discard.
Push fit the new valve onto the rubber hose you just disconnected the old one from.
Fish out your rubber grommet from the hot water and push back into its hole on the crank case cover, being careful not to split or push in too far. If the grommet is knackered, new ones can be ordered from Skoda or Ebay.
Once the grommet is back in its place, push the new valve into it. I used some of the water as a lubricant to ease it in.
Then, just make sure the valve and grommet are snug and it is a case of putting everything back together.
Re-attach the pressure pipe by putting the bottom part in first, then pushing the top part back down, making sure both clips fully engage (click).
Connect the plug at the top of the pressure pipe back onto the pressure pipe.
Place the black plate back to its original position and tighten the torx screws up (7nm tightness).
Finally; clip the rubber pipe to the lower right side and the wire for the plug to the top left . Remember the sneaky wee plastic pipe under the pressure pipe at the top - clip that back in too to avoid any chaffing.
That's the job done.
Don't fret too much if the remnants of the old valve are not in the grommet. Chances are they fell inside the case and were chewed up long ago, hopefully not damaging anything.
From what I gather the crank case air intake valve breaking is a common fault, so I hope the guide assists someone.