What cases a flex pipe to break ? - Hyundai Motor 1999 Elantra

Could be your o2 sensor(s) i had an upsteam and downstream on my Mazda protege.

You can cut out the Y pipe and replace it with a flex pipe from parts store, then clamp each end of the flex pipe, the pipe diameter will be 1-7/8 or 2 inch, also for the pipe replacement piece would work from a sunfire or cavalier from 1995 and up, might need to replace the muffler strap too. as it can break from rusting, if not already rusted and broken.

Take it to an independent (not a chain) muffler shop and have it replaced. I'm guessing around $200. Also, have the engine mounts checked. If they're worn, the engine rocks too much and breaks the flex pipe.

You are right. The engine flexes differently, but not less. The designers that put the engine sideways also put the flex pipe in the design, and the shop is just saving money. I'm a mechanical engineer, and I can tell you the stresses on the joints will be higher without the flex pipe. I can't say for sure something will crack, but it is certainly more likely.

The broken flex pipe can easily be fixed with a generic flex pipe for less then $100.
The catalytic converter is after that, so has nothing at all to do with it.
But cracks can also brazed or welded to fix.
However, the reason flex pipes break is from excessive engine movement.
That almost always means a loose bushing on a motor mount.
So do that first.
Should be less then $50.
Never take a car to a dealer unless you absolutely have to.
They charge twice what it should cost, because they want to sell new cars, not fix older ones.

if it is at the flex pipe, it is difficult to just get a patch.....i would just replace that section of the pipe, or worst case scenario, get a whole new exahust, but get the exhaust shop to use your catalytic converter and muffler, if there are no problems with them, this will cost you heaps

Your exhaust pipe under the engine is a flex pipe connection to prevent it from breaking with engine movement. there is a bracket the holds the pipe mounted to the oil pan, check and see if this bolt is still there it often falls out. Hope this helps.

Advance auto and auto zone sell just the flex pipe. You will need to have someone cut the old one out and weld the new one in. costs about $20 for part vs $300 for pipew/catalitic converter attached.

if it is a 4 cyl they are known for the flex pipe breaking the only fix is unfortunely replacment as far as the smoking sounds like you have a leak onto the exhaust have the oilpan and rear main checked

Yes you can obtain the parts from after market. The Flex Pipe is installed on all cars hows engine is built in transverse. if you accelerate the engine tries to turn against the crankshaft rotation. W/o flex pipe your exhaust will be broken after a couple of minutes. The flex pipe acts like an accordion and eliminates this small "turns".