crush washer mating surfaces after grit blasting

[Funkatronic]

I have had an engine cover grit blasted for painting and noticed that a couple of the areas of the case that were paint free and had exposed shiney metal eg around the holes where the oli sensor interfaces and the oil filler cap have been roughened up by the procoess

do i need to polish these back to mirror finish as they were before to ensure the crush washers/o rings seal properly?

thanks

ali

[big pete]

Wouldnt have thought so unless they are really pitted, I would be tempted to put a small smear of Blue Hylomar on with it to be sure (good enough for Rolls Royce!)

[utopia]

If you're talking about the filler cap, and pressure switch seals, I would think you'd be ok leaving them as they are.
Grit blasting would produce a uniform, dimpling of the sealing surfaces, which would not create a continuous leak path across them, unlike for example scratches running across the surfaces would.
They're not under much pressure, and aren't continuously immersed in oil anyway, ie they are "splash" seals more than anything.
That said, I think I would still give them a quick clean up with fine wire wool or something, just to take the roughness off. The danger here is that you could go too far and alter the dimensional form of the sealing surfaces, which may then cause a leak, so I'd just give them a minimal clean up, trying to be even all over. Try to avoid making any lateral scratches, ie from inside to outside, just work round in a circular motion.
O-ring seals are very reliable in this sort of situation though, so you might not need to bother cleaning the surfaces much at all.
And if they do leak, it wouldn't be that hard to deal with retrospectively, I would have thought.