There is a awesome thread on the SXOC on this... I have done it on my engine bay and it works a treat and looks good as new...
1) squirt wd40/other water repelant on major electrics and bag with carrier bags (Fuse box, CAS, Alarm Siren, Boost Controller valve etc) AND also bag the Unduction Kit(s) but dont squirt with WD40!
2) Spray all engine bay with engine degresant (I use Autoglym Engine and machine degresant) and in very dirty areas use a cheepo paintbrush to agitate and spray more of the degresant (Dont be shy with it)
3) Rinse off with hose with no attachment with a decent stream of water but not a jet. Try and keep away from the electrics.
4) Unbag electrics and unduction kit and run the car for 15-20 mins with the bonnet closed.
5) Spray (Important) Autoglym Tyre dressing all over the engine bay. Get it everywhere, i mean everywhere(Well apart from induction kit and manifold), cables, hoses, electrics, bodywork, pipes, plastic trim etc. It comes out a milky substance so you can see where it is and dont worry about it gathering in places.
6) Close bonnet and leave for 1 Hour.
7) Open bonnet, stand back and admire your work. Wipe up anywhere that the milky substance (ooh-err i mean from the Tyre dressing)
Mine S14a After a good clean...
I cant take all the credit... I did the work but the guidence came from Mr OCD on the SXOC.
:thumbsup: