I have been working to restore my great-grandpa's old 1985 Toyota Pickup 4x4 22r and was working on welding some exhaust leaks before the muffler when I noticed a small hole in the front of the muffler. I didn't think much of it and added it to my list to repair later or just replace the muffler but after I looked a little closer it appears to be intentional. In the picture you can clearly see its a hole drilled in the bottom of the muffler.



Sure enough I found a receipt in the glove box where my grandpa paid to have a shop drill a hole in the muffler. I have done some searching on this forum and others and found people drilling holes in the muffler for "better performance" (unlikely) or improved sound or drainage. The two previous owners (my great-grandpa and my grandpa) were both Kansas farmers that never used the Toyota for anything other than a work truck so I can't imagine they were attempting to make the exhaust louder or worried about hp gains.

Is there any other reason why people would drill a hole in these mufflers? I'd prefer to patch it up or replace the muffler because hearing the exhaust leak drives me crazy. I'm worried it was for condensation drainage or maybe to cover up a problem with a plugged muffler. It seems unusual for my grandpa to pay anyone to do a small job for him, especially something like drilling a hole, so I'm worried it was recommended to him by someone at a local shop.

Any thoughts?

 

My muff has a small hole like yours in that pic to drain condensation, but no clue why you would do it otherwise if it didn’t come new with the hole…..

 

Likely a condensate drain, supposed to lengthen the mufflers service life by minimizing corrosion.