I am running a 1979 PA28-236 Dakota, with a standard O-540-J engine, and have a problem with the exhaust downpipe cracking and then separating at the fange to the manifold. This seems to always happen on cylinder 1 (front right when looking from the cockpit). I had a similar problem with cylinder 3 (next to cylinder 1) but much less frequent.
We have welded the pipe, twice, only for it to crack and split again by the next 50 hour check. Recently I replaced the downpipe with a brand-new part, only for this to crack and split within 25 hours of being fitted. The plane does 150 hours a year, has a high time engine (1,800 hours, 18 years SOH) but in every other respect runs beautifully.
Any ideas on what is causing the pipes to crack? There is no obvious rubbing or chaffing on any other part.
We have welded the pipe, twice, only for it to crack and split again by the next 50 hour check. Recently I replaced the downpipe with a brand-new part, only for this to crack and split within 25 hours of being fitted. The plane does 150 hours a year, has a high time engine (1,800 hours, 18 years SOH) but in every other respect runs beautifully.
Any ideas on what is causing the pipes to crack? There is no obvious rubbing or chaffing on any other part.
