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Peugeot 307 Exhaust Leak

Alright gearheads, I'm tearing my hair out here. My 2004 Peugeot 307 (gasoline engine) is throwing a hissy fit. The check engine light's on, power's way down, and I'm burning fuel like it's going out of style. Diagnostics point to a faulty exhaust temperature sensor. I suspect there might be a small leak somewhere in the exhaust system before the sensor. Could this be the culprit? Mileage is at 230858 km. This is driving me nuts!

4 comment(s)

I had similar gremlins in my old Volvo V70. Same symptoms – check engine light, power loss, and drinking fuel like crazy. Turned out it was also a dodgy exhaust temperature sensor, which was triggered by a small exhaust leak further up the system. Have you checked the exhaust manifold for cracks or loose connections? A tiny pinhole can cause havoc with the sensor readings.

Interesting! I did a visual inspection, but didn't spot anything obvious on the manifold. Was the leak on your Volvo easy to find, or did it take some digging? I'm wondering if I should just bite the bullet and take it to a shop for a smoke test.

It was a pain to find, to be honest. It was a hairline crack on the manifold, only visible when the engine was hot. Eventually, I caved and took it to a shop for a smoke test, and they found it in minutes. For the Peugeot, it's worth checking the flex pipe too, as they can corrode and leak. Might be worth going to the shop, could save you a lot of time and headaches. They will probably replace the sensor anyway.

Thanks for the advice! I took it to a local garage, and you were spot on – tiny crack in the exhaust manifold, throwing off the exhaust temperature sensor. They welded the crack and replaced the sensor. Cost me 265€, but she's running like a champ again. Appreciate the help!

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