This is pretty easy, cheap and necessary to do every so often. This is done on a 1.8lt injected Mk1 Golf. Carburetor models are different.
The airfilter is located under the fuel injection system and, while no visible, is pretty easy to access. You just need to unclip and lift off the fuel injection system to access the filter's housing. You do not need to disconnect the fuel injection hoses to do this.
Use a screw driver or 7mm socket to remove the tube out of the way. This just makes lifting the fuel injection unit out of the more easy.
There are 4 metal clips, one in each corner, holding the fuel injection system to the top of the air filter housing. These can be removed by hand but a large screw driver can help to pry them off. You may need to remove the battery to access some of them.
The fuel injection system is now only attached with the threaded fuel line affording it some degree of maneuverability. Carefully lift it up to reveal the old air filter, then slide the old air filter up and out of the housing.
This is the reverse of the above. The orange rim of the air filter faces upwards. Be careful not to crush the filter when inserting it and be sure to check if any of the clips are getting in the way. When everything is in place and the air filter is 'level' in its housing, clip the injector unit back into place.
Replace the breather and air intake hoses.
Since we've been moving the fuel lines around it's worth checking these are not leaking (it's very unlikely anything is wrong, but they could be old and worn).
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