I called to schedule the head gasket work at the dealer and reminded them I wanted to make sure we diagnosed the tapping sound before we got into it. He said that “we are fairly positive that it it the rod bearing”(they listened to it briefly when working on the converter) I responded with the possibilty that it was a valve lash adjustment; he said “have not seen that problem” I asked what about piston slap and his response was “probably not”. This sounds serious to me and wonder how this so-called dependable engine with 91,000 miles would have this problem?
After rereading your original post, you indicated that the tapping went away as the engine warmed up. Usually rod bearing knock gets worse as the engine warms up because the oil gets thinner. Also rod bearing knock will intensify as the engine rpm comes up and then quiet. If the problem is truely a worn rod bearing that would show up in the oil pressure, where the red oil light would come on when the engine is fully warmed up and idling, like just off a freeway at a red light. Also a mechanical check of the oil pressure would show the drop in pressure as the engine oil was warmed up.
Rod bearing knock is the kiss of death to an engine. Putting new head gaskets on such an engine would not be cost effective. A better approach would be to have the present heads put on a new short block.
I would have a different mechanic give you a second opinion on the noise and explain your options to you.
Good Luck on this.
Thanks for your insight, Yes the sound does decrease as it is warmed up. I had a former Subauru mechanic check and listen to the car before I bought it and he did not detect any concerning sounds. The car was completely warmed up when he had it. I later started noticing the noise in the mornings and so the story goes… Sounds like I need a second opinion. They also said it could stay like that for some time and you’ll never have a problem from it!?!