All:

I just replaced the O2 sensor in my 1987 22re with a brand new bosch unit. Upon firing it up after install I noticed a new sound which sounds like a exhaust leak. I don't think I cracked the manifold upon installation of the sensor (I made sure to tighten everything when the engine was competely cool). Does the gasket which is supplied with the sensor have an 'up' side and 'down' side (directions did not indicate this)? Or, will is just take time for the gasket to 'seal'? Is there something else I should look at?

Cheers.
Ari

 

You can use a little high temp silicone (02 sensor safe) on the gasket. No up or down that I know about - confirm that it's leaking from the 02 sensor area.

 

I believe some O2 sensor gaskets have an up & down. I'm not sure which brand though. The best thing to do is call the supplier, they might be able to help.I do believe Bosch does have an up & down.

 

If your sensor bung is original my guess is that over the 20 years the thing rusted up a lot and is rough and pitted out making the seal less than perfect. The sealant idea sounds worth a try, but as mentioned make sure it's sensor safe sealant and able to stand up to the very high temps. I'm thinking that the copper coat stuff may be the one to look into though. Working on a 20 year old exhaust system is just asking for worms-can-open