Changing the glow plugs on Volkswagen Golf IV - 1.9 TDI

Remove the engine cover with a 10 socket ratchet (3 screws + the oil dipstick)

Remove the ignition rail by unclipping it then extracting it to the side

The glow plugs are accessible

Clean with a blower

Apply penetrating oil to make it easier to remove the spark plugs.

Loosen the 4 spark plugs using the spark plug wrench and ratchet then remove them from their wells.

Lubricate the thread of each spark plug with the gauge.

Check the correspondence between the new and old spark plugs (size, thread, connectors)

First, screw the 4 spark plugs back in then tighten with the ratchet.

Do not overtighten the spark plugs to avoid breaking them.

Reposition the ignition ramp

Perform an engine start test

Replace the cover (the 3 screws and the gauge)