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Thread: Some tips for a Block Heater install on Mazda3/5

  1. #1
    n00b

    2007 MazdaSpeed 6 GT

    Join Date
    Feb 2014
    Location
    Earth
    Posts
    2

    Some tips for a Block Heater install on Mazda3/5

    Most of you won't have access to this as block heaters are a Canada only dealer option.
    PN #0000 88 25M3 CA
    PN #0000 88 25M5 CA

    Tools needed

    3/8" ratchet
    14mm Allen/Hex socket for 3/8"
    Large philips socket for 3/8"
    10mm socket for 3/8"
    24mm 1/2" shallow socket
    1/2" male to 3/8" female adapter
    Needle nose pliers
    Side cutters

    I had to install one of these today and was very much at a loss as I could not find any information about this anywhere, I was guessing wildly with everything but finally got it all done, tested and working, took me about 3 hours while using a hoist, if you know what you're doing, it should take about 1 hour. Hopefully my info here will help people get from the 3 hour mark down to the 1 hour mark by learning from my mistakes.

    Both of the part numbers above are the same kit, so if your dealer gives you the Mazda 5 version, it's totally fine, the parts are identical and they will work.

    Now, first things first, remove the larger section of skid plate, the further back section with the hole for accessing the oil filter, that is the piece that needs to be removed, I didn't take many photo's as coolant was involved and I didn't want it all over my phone so you'll have to figure it out as you go along. Anyway, it's held on with two clips, one on each side at the front, three 10mm bolts around the front in those deeper pockets, and four more 10mm bolts on each side near the wheel wells (two on each side)


    Once that is removed, take the cap off of the coolant reservoir, make sure your engine is not warm as it's under pressure and you will burn your face off with extremely hot coolant going everywhere at mach twelve, this is standard stuff you should know before trying to do a job like this, but I still feel it's worth mentioning, continuing on, if you're facing towards the front of the vehicle (facing in the direction as if you would be driving) the petcock is on the lower left corner of the rad, you need to drain the coolant once the reservoir cap is open to release pressure, use a clean container to catch the coolant if you want to reuse the old stuff, it's normally good for about 5 years or so, depending when it was last flushed, it might be worth while to keep it and reuse it once it's all done if it's still recently new, if it's your factory coolant, I highly recommend this is when you should also perform a coolant flush, however we won't get into that here.
    Now, you open the petcock with the larger philips socket for a 3/8" ratchet, I had to use my ratchet to crack it open, but once it was open I unscrewed it by hand as these are VERY BRITTLE! I can not stress this enough, treat it like it's a very delicate piece of glass because if these break, you need a new rad, it's all one piece on these cars.

    With the coolant now drained, the location of the block heater is on the upper left side on the rear of the engine block. The plug you need to remove is a 14mm Allen/Hex plug under the exhaust manifold, there are two ways to access this, from under the car reaching up to the left of the exhaust manifold, or from the top reaching down from the left of the battery, both are very difficult areas to get into, I had to go from under to get a the 14mm socket and 3/8" ratchet on, and then go on top to have leverage on the ratchet to crack loose the plug only getting in about 1/16th a turn every time so it's needless to say taking this out took for ever, this process of figuring this out is what took me nearly an hour to try and get the right angle and figuring out which socket size, extensions, etc would all work best, for me it was a 14mm Allen/Hex socket and a 3/8" ratchet, other combinations might work better for you, but I tried a lot of different tool combinations and this was the sure fire way I was able to get it done.

    Here's a little video of where the plug is, you can't physically see it with your own eyes from the top or the bottom so this entire job here is done by feel.


    It's the one with red thread sealant around it, this is NOT Loctite, it's sealant so coolant doesn't go everywhere when the metals expand and contract from engine temperature


    Now, before it's completely removed, have your drain pan ready again as more coolant will be coming out of this hole, it's going to happen, just go with it, let it happen and accept fate.

    Once I had that plug removed, it was just a matter is screwing in the actual block heater itself right into that same hole, again I was able to get it started by hand from up top reaching down to get it in, I was standing on the right side (passenger side) of the vehicle using my left arm down around to the Driver side of the manifold to get access to it. With the threads started I was curious as to how the cord will go as the end has a 90 degree so just making some metal notes of how I was going to run the wire, I angles the block heater at a 45 degree angle going from the top passenger side of the engine, down to the bottom drivers side of the engine, if that makes sense, imagine a line going from the passenger headlight down to the driver side fog light, this allowed the 90 degree plug to be plugged in and run up along the coolant hoses without touching the exhaust manifold heat shields providing some extra protection from melting the cable.

    I don't know the torque spec, I just tightened it until it had a decent amount of friction on the 24mm socket using the 1/2" adapter on a 3/8" ratchet (I did it like this because I didn't want to have too much leverage on the block heater but using a 1/2" ratchet is fine, just be careful because it's just a brass plug and can easily be stripped. Once it was snugged up, I just kept going with my 1/16th of a turn until I had it at the angle I mentioned earlier so I could run the cable

    Next it was time to run the cable, like mentioned, I ran it up along the coolant hoses, between the battery and air box towards the drivers side of the engine bay, down the wiring harness by the drivers side headlight, and from there I picked a super stealth location to hide it along the front lower grille in the bumper, I chose to put it out the grille right at the top middle so I can tuck the plug up behind the front plate for when it's not in use there isn't a plug dangling around all over the place, this also keeps it safe from ice build up over the winter.

    Hope this helps anyone out this winter, I wish I had this information earlier today as it would have helped out a lot, and a lot of the time today was spent searching for information on tool sizes and location of the plug/cable routing/etc and I ended up giving up searching for ways to do this and figured it all out myself.

    So, that's how I did it, if anyone has any other tips of information, feel free to add it here to help anyone else out, it wasnt a hard job, it was just figuring everything out
    2007 MazdaSpeed 6 GT, Method/Water Injection, COBB AccessPort, GT3071, CorkSport FMIC, BSD, DNP Equal Length Manifold, JBR EGR Blockoff, BC Racing Coilovers, CP-E 3" Catless Downpipe, ACT Racing Clutch, ACT Prolite 11lbs Flywheel, PTP High Pressure Fuel Pump, CP-E Rear Motor Mount, CorkSport Short Ram Intake.

  2. #2
    n00b

    2007 MazdaSpeed 6 GT

    Join Date
    Feb 2014
    Location
    Earth
    Posts
    2
    I forgot to add that once the cable is run you also need to put the coolant back in the reservoir, and let the vehicle idle for about 5 minutes with the heat and fan on full blast, keep topping off the reservoir to the max line as needed, and after about 5 minutes of idling, rev it to around 2000 to 3000rpm and hold it there for about 2 to 3ish minutes, and thsen let it idle for another 5, every time you let it idle, just keep topping up the coolant reservoir with the coolant saved, or a 50/50 mix if you're adding new coolant to the system until it is blowing heat at idle and the reservoir stops going down.

    Only put the cap back on once the cooling system is fully bled of vapor locks, not only will you not have heat if you fail to do this properly, but you can also burn out the block heater element if it's turned on and there's no coolant around it to warm up, it will just get hotter and hotter heating itself until it burns out and have to do this all over again, so make sure you're cooling system is 100% good before putting the reservoir cap back on and calling the job done.
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  3. #3
    Registered Member

    2013 Mazda 3 GS Skyactiv 6sp auto

    Join Date
    Oct 2017
    Location
    Winnipeg, MB
    Posts
    2
    Thanks for this thread. This has to be the worst install I have ever come across. It's unfortunate no one has commented on this. I cannot find a 14mm hex bit with a 3/8 driver, only 1/2 inch. Even that in my town is almost impossible to find except in a set of 20 or 30 bits. Ugh. How much torque does it take to break the seal? I can barely get my hands in that space. I bet Mazda has a special tool in Canada for this.

    Again, thanks for the help. I am going to try this again and hopefully, I can find a bit to do it right.

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