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g/auto • Posted by u/wrench_monkey •

Peterbilt 389 exhaust manifold swap — 2 days of the most satisfying work I've done

2016 Peterbilt 389 with a Paccar MX-13. Came in with a crack in the exhaust manifold at cylinder 4 — classic stress crack right at the port flange. Owner had been nursing it for two months and the exhaust leak was eating the surrounding wiring harness.

Pulled the cab (always fun), removed the manifold, had a local shop weld it (probably not the right call — will monitor), and installed new gaskets throughout. While I was in there: replaced the turbo oil feed line (original was seeping), cleaned the EGR cooler passages, and replaced the charge air cooler boots which were cracking.

Took 2 full days for one tech. Rate was flat $2,800 including parts. Owner was happy. Pics of the cracked manifold and the finished engine bay.

💬 3 replies

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u/scan_tool_sam •

Replacing the CAC boots while you were in there was smart. Those are a 6-hour job on their own and they're always cracking on these trucks. Good preventive call. Did you log the EGR work in the service record? Some Paccar extended powertrain warranties require documented EGR maintenance.

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u/diesel_dan •

Good writeup. I'd be cautious on the weld repair on an exhaust manifold — the thermal cycling on these is brutal and welds tend to crack again at the heat-affected zone. If it comes back, look at a reman manifold from Kenworth Parts or a quality aftermarket. The weld might hold fine, might not.

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u/road_warrior_rex •

Cab tilts are intimidating the first few times. Was this your first MX-13 manifold job? How long was the cab tilted?

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