Change a CAT
- Diffuser off (Rearmost part of the undertray)
- Soak cat nuts in penetrating oil for a few days before hand. Undo nuts from Cat. (15MM), use Loctite Freeze and Release to break the nuts free of rust etc. It really does work.
- Cut off those that won't move, swear profusely.
- Wiggle the Cat, silencer and flexi until it all comes apart (If necessary remove rubber mount from the flexi)
- Offer up CRP and fit the new stainless steel bolts in place not forgetting the gaskets
- Tighten the new stainless steel nuts progressively as your CRP may not be an exact fit
- Find gaskets on the floor undo the bolts and refit corectly
- Refit diffuser
Job is a carrot, first time will take hours as the bolts are all rusted, second time is a doddle. While the cat is off press out the studs with a vice and a suitable socket, makes things easier next time.
Note that some grades of SS bolts may seize over time with the extreme temperatures; the only way to remove them is to apply pressure until they shear, then they will need to be renewed (removal will be necessary once a year for MOT if you are fitting a CRP). If fitting a CRP, normal steel bolts will be fine as the constant removal-refitting is enough to keep them from rusting up.
The use of copper grease can help prevent seizure.