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Thread: Help needed with Exhaust Manifold removal for 2007 Mazda3 S with 2.3 liter engine

  1. #1
    Registered Member

    2007 Mazda Mazda3 S

    Join Date
    Jun 2017

    Help needed with Exhaust Manifold removal for 2007 Mazda3 S with 2.3 liter engine

    I'm currently trying to remove the exhaust manifold on a 2007 Mazda3 S with the 2.3 liter engine. The issue stems from the upstream O2 sensor seizing up completely and the nut rounding out when I tried to remove it. Yes, I tried PB Blaster but I'm far beyond any hope for removal at this point. The O2 sensor is now completely destroyed and I basically have to drill it out and weld on a new bung or just replace the entire exhaust manifold at this point.

    I've removed all the bolts and nuts attaching the exhaust manifold to the vehicle but can't seem to route it out of the engine bay. I've tried over the course of a few days with someone helping me. I've removed just about everything I can to get the most clearance including the heat shields around the sway bar and brake lines both on the firewall and the steering rack. It just doesn't seem to be enough and will not come out. At this point, things are getting scratched up pretty bad and the thin foil around the exhaust below the firewall is ripped up pretty bad.

    Does anyone have very detailed instructions on how exactly to remove the exhaust manifold for this particular model? Or does it need to be cut to be removed for this vehicle? At this point, I'm considering replacing the exhaust manifold so cutting the old one isn't out of the question. I just wanted to ask for tips before taking that time-consuming route and being forced to replace the exhaust manifold just for the 02 sensor.


  2. #2
    Registered Member concept's Avatar

    2014 Mazda3 S GT auto, 2008 MX5 6-speed

    Join Date
    Mar 2009
    San Diego
    Have you already looked at a factory service manual for R&R steps?
    2014 3S GT, Deep Crystal Blue, Eibach Pro-Kit, Enkei PF01s, Koni Sports
    2008 MX-5 Touring (Mazdaspeed CAI, HIDs, Progress/Koni Sports/Racing Beat sways, Magnaflow)
    2002 Protege ES (no mods. but among the best-handling stock cars I've ever driven)

  3. #3
    Registered Member

    Mazda3 Sport GS-Sky 2012

    Join Date
    Sep 2014
    concept's right, as usual: read the manual. On the other hand, there may not be any procedure to remove and replace an exhaust manifold with the engine in the car. After all, the manifold is already on the engine when the engine goes in the car. It usually comes off only during an engine rebuild, which of course is done out of the car. I'm not saying you need to pull the engine (or drop it out the bottom, since it likely goes in from the bottom) to replace the exhaust manifold, but I am suggesting that there might not be a reasonable method to do the job.

    I assume that the path for the manifold is out the bottom. I would look at what can be removed to provide a clear path, including if necessary the crossmember or subframe... complete with suspension. It may seem extreme, but it's worth considering.

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