All I can say is WOW!

The ugly one is the front sensor. I figure the junk in the tube is rust off of it. You ever see this before???

My real question is do I replace both? I don't know if they should be replaced in pairs.

 

The rust is probably from washing the engine. Just replace both and put some silicone around the lip of the cups that cover them to keep water and moisture out.

 

Thats not even bad, you should see the ones that come out of the 5.3 trucks the backs get way worse then that. I would just replace the rear one as the front looks new. Clean out the holes put everything back together and put some rtv around the outside of the plugs to stop water from getting in.

 

Thanks guys. Good to know it's a common problem.

 

x2 on using RTV on them. There was a TSB for truck motors advising dealers to add RTV to knock sensors to keep coolant out, I guess it can affect the car motor's too.

 

yep, did my 6.0 last week.