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Thread: Mazda 5 Oil Cooler Replacement & YOUTUBE WARNING

  1. #1
    Registered Member

    2008 Mazda 5 & 1990 Mazda Miata

    Join Date
    Dec 2016

    Mazda 5 Oil Cooler Replacement & YOUTUBE WARNING

    Greetings all,

    I'm back again for another fix on Zuzu, my 2008 Mazda 5 with 178k miles. This time it was my leaking oil cooler. Let me start off with the BIGGEST WARNING EVER:

    There is a YouTube Instructional about a man fixing his leaking oil cooler with make-your-own gasket material. For the love of all that is holy on this amazing planet, DO NOT DO THIS. I cannot stress this enough, and you will see why. The only thing I can recommend from his tutorial is the identification of the leak and disassembly to the oil cooler, nothing more.

    I purchased my replacement oil cooler off of Ebay. I took a gamble here because as something as important as the oil cooler, I would really only trust with OEM. Instead of posting a link that inevitably expires, here is a screenshot of what I purchased:

    Ebay Listing by Monk Ratava, on Flickr

    The symptoms were leaking massive Oil, about a 1-2 quarts every gas fill-up. The leak would drip onto the oil filter housing and the lower coolant line attached to it.

    Disassembly was straight forward. In order:
    1. Drain both the coolant and oil
    2. remove the lower Oil filter cap - 75.6mm Filter Wrench
    3. remove the two coolant lines - Clamp style
    4. disconnect the oil sending unit/remove the oil sending plug (green plug) - 15mm open end wrench
    5. Loosen Oil Cooler Bolt - 15mm (May require impact wrench)
    6. remove the 4 Oil Filter Housing Mounting bolts. - 10mm
    6a. If you have the older "black" style oil cooler, one of the 4 bolts will require an open wrench due to clearance. New "silver" style is smaller.

    Now comes in that YouTube tutorial I mentioned earlier; Not only does it not fix the oil leak as many people have commented, but it also sets the next owner up for failure when truly fixing the leak. I don't know how much it leaked when the previous owner had my 5, but I can confidently say that their "fix" leaked a whole lot under my ownership. Your jaw will now drop as much as mine did:

    Shitty Seal by Monk Ratava, on Flickr
    Botched Seal by Monk Ratava, on Flickr

    Wow. Awful. Not only did this not fix the leak, but it took me 2 hours to carefully scrape off and not have a silicone shrapnel land in the oil filter housing. Judging by the photos too, I would wager the gasket material probably shot into the oil (I cringe thinking this happened to me). Another downside to this make-your-own-botched seal is the mating surface to the oil cooler is slightly corroded. I highly recommend getting a new Oil Filter if your previous owner attempted to fix this way. After 2 hours of scrubbing with PB Blaster and a hotel key card, I finally got the surface to look like this:

    Cleaned Oil Cooler Surface by Monk Ratava, on Flickr

    Much better! Reinstallation was pretty straightforward. For the Engine Block Gasket, I made sure to use the reticle side and the opposite corner to line it up to the block as straight as I could:

    Block Seal by Monk Ratava, on Flickr

    Be sure to torque down correctly and reconnect that oil sender plug:

    Oil Cooler Top Bolt: 24-26ft/lbs
    Oil Filter Housing bolts (4): 24ft/lbs
    Oil Filter bottom cap: 7ft/lbs.

    Reassembled by Monk Ratava, on Flickr

    And that's it! Fired it up and absolutely no leaks! Be sure to top up all fluids when you are complete and properly bleed your coolant system to avoid any overheating! Let me know if there's anything I should tweak in this post. I hope you learned a lot from it too! Do leave a post if you have any questions.

    Last edited by Affin_Roadster; 06-21-2017 at 09:29 PM. Reason: additional info

  2. #2
    Registered Member

    2008 Mazda 5 & 1990 Mazda Miata

    Join Date
    Dec 2016
    My friend was able to send me more photos he took of both the old and new oil coolers.

    Parts Numbers by Monk Ratava, on Flickr

    New Oil Cooler by Monk Ratava, on Flickr

  3. #3
    Registered Member


    Join Date
    Apr 2018
    I'm the the process of doing the same thing to my cx-7 as I'm having the same issue and was seeing if you had problem taking off the hoses from the old oil cooler?

  4. #4
    Registered Member

    2009 Mazda5 Sport

    Join Date
    Mar 2018
    If you have the plastic canister filter housing, this looks like a good time to change over to a spin on filter housing.

    Good luck with your endeavor.

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