Inspecting my exhaust system (newly replaced post-cat) today after something caused a sudden increase in noise while driving/accelerating, I discovered a nice round hole (bit smaller than quarter-size) in the pipe a few inches aft of the cat on the passenger's side.

Apparently there is/was bolt in this position for access/testing that has deteriorated and finally gave out, popped off, and left me with a noisy opening (no thread as far as I can tell).

I assume this happens after a while with all bricks having this odd feature.

So what's the best way to fix? Find a big nut to fit and weld shut?

Thanks for any tips,
Peter
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'91 940T 153k; '92 745 186k

You're right about that hole's purpose in life but it belongs forward of the cat for a pre-cat exhaust sample. The holes is generally 18mm thread. If you cannot find a drain plug or short bolt to fit it, you can use a spark plug for a 1950s to '70s Ford (6 cylinder truck eng to 1985). They are tapered seat type but the correct thread.

Haven't seen one aft. But, I dropped in a universal, it had a opening in front of the cat, local muffler shop dropped in a plug and spot weld it. Said they normally will vibrate out.

Sorry... I meant "fore" rather than "aft" re position of this hole in relation to cat. Needless to say, I won't be winning any regattas any time soon.

Thanks for the help though.

Peter
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'91 940T 153k; '92 745 186k

Are you sure that's not for an O2 sensor?

Klaus
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(V♂LV♂s 1975 164, 1995 854T, 1998 V70R)