Planning the next
AO Silver Member
Join Date: May 2007
Location: United Kingdom
The way I did this ( very easy and keeps it standard ) -
1. Remove the airbox lid allowing the brass inserts to come out with the bolts.
2. Remove MAF etc.
3. Drop the lid in a strong solution of citric acid. Leave for a couple of days agitating as often as you can.
4. Remove lid from citric acid and rinse under a tap.
5. You can now easily remove the brass insert off the corroded screw.
6. Put the brass inserts back in the filter housing body ( with a little superglue or similar to lock them in place ).
7. After reassembly, re-fix the lid to the box with ideally brass screws or, if not, stainless steel*. DO NOT USE ZINC PLATED SCREWS.
The only problem is getting citric acid. You used to be able to get it in pharmacies but you're likely to be viewed with suspicion these days ( citric acid is used in illegal drugs ). As an alternative, Coca Cola or Lemonade should work but may take longer.
* Stainless steel is quite close to brass on the anodic scale so there should be very little corrosion between the two metals.