Guide 2016~2021 CX-9 DIY Transmission Fluid Drain and Fill + Filter Change

[Silly Wabbit]

Hope this question isn't too stupid.
If I have to remove the airbox to get access to the dipstick etc, then how can the car be in idle when checking the level using the dipstick? Is it ok to idle while the airbox is disconnected like that? I didn't think it was...
Also...you fill it up using the tube that the dipstick is in right? there's not a separate fill hole, just the dipstick tube itself?

I actually plugged in the top half of the box and used zip ties to hold the filter in place. Proceed with extreme caution because the fan can activate at anytime.

 

[omarh93]

I actually plugged in the top half of the box and used zip ties to hold the filter in place. Proceed with extreme caution because the fan can activate at anytime.

But is it really different if you're idling versus just with the car off?? The dip stick doesn't give the same result?
Isn't it crazy how Mazda made it so difficult to check the level while the car is running?

 

[audirt]

But is it really different if you're idling versus just with the car off?? The dip stick doesn't give the same result?
Isn't it crazy how Mazda made it so difficult to check the level while the car is running?

I'm not a mechanic so take my answer with a grain of salt.

I think the big difference is that they want you to check the level when the ATF is within a specific temperature range.

I tend to agree with you -- my plan is to run the engine until the atf gets to the right temp, then turn the car off and quickly remove the airbox to check the fluid level. I think the thing to keep in mind is that the moment you turn the car off, the fluid will start cooling back down which could conceivably affect your reading on the dipstick. But my belief is that it won't cool down instantly, so it should be fine. (If I have to add more fluid then my method will become a PIA...)

 

[dodgerfan356]

I'm not a mechanic so take my answer with a grain of salt.

I think the big difference is that they want you to check the level when the ATF is within a specific temperature range.

I tend to agree with you -- my plan is to run the engine until the atf gets to the right temp, then turn the car off and quickly remove the airbox to check the fluid level. I think the thing to keep in mind is that the moment you turn the car off, the fluid will start cooling back down which could conceivably affect your reading on the dipstick. But my belief is that it won't cool down instantly, so it should be fine. (If I have to add more fluid then my method will become a PIA...)

I'm not a mechanic either, so I could be wrong, but I think this would actually result in underfilling the transmission. The reason they require checking the dipstick with the engine running is that when the engine is off, more fluid drains back into the pan, so you actually get a higher dipstick reading with the engine off than with the engine on (even at the same temperature).

I actually just did a drain and fill today. I checked the dipstick cold beforehand, and the level was way above the fill line, almost at the top of the dipstick.

 

[yrwei52]

But is it really different if you're idling versus just with the car off?? The dip stick doesn't give the same result?
Isn't it crazy how Mazda made it so difficult to check the level while the car is running?

Yes, Mazda really made it so difficult to check the ATF level.

The step 6 in the Mazda Workshop Manual specifically says “while leaving the enginf idling” when you take the measurement of the ATF level at 122°F. I also would shift transmission into every gear then measure the ATF level with the engine idling. When engine is idling, the AFT pump is functioning and circulating the ATF everywhere in the transmission including the torque converter which has a half of the total ATF quantity. That’ll bring down the ATF level in the pan significantly. It’s similar if you check the engine oil level with the engine running, the oil level will be much lower in the oil pan.

Here FerrariF1 originally thought his ATF level from factory was fine with engine stopped on his CX-5 2.5T. Once he rechecked with engine idling, he needed about 600ml (0.635 quart!!!) to bring the ATF level to the Full mark (although the ideal level should be at the middle block area). Mazda under-filled the ATF in his transmission as usual at the factory. That’s why you don’t re-fill the same amount of fresh ATF as drained ATF because the factory fill usually is too low.

He also did an experiment and found the differences on ATF level in different ATF temperatures on his CX-5 with 2.5T:

You guys were right, I checked the ATF while idling and it was low. The ATF was at around 25-30 C (77-86 F). I added 600ml and it came up to the middle of the 2 lines, so perfect. I don't think ATF expansion is that great that I need to check at 122F, and I'm guessing if I were to check at 122F it would be closer to the top line.

I also changed the rear diff and front transfer case, and they both took about 0.5L each. Not too complicated.

Update: I warmed up the transmission fluid to 51C / 123F and re-checked level (car idling, level surface) and it was just below the Full line. MS Paint artwork attached.

Summary: added 600ml to factory fluid to bring it up to full level. I did not drain and fill since car has 30K km / 18K miles.

View attachment 320245

Honda and Toyota definitely make this easier:

Yes, my 1998 Honda CR-V and friend’s 2002 Honda Odyssey all just require the engine in “operating” temperature, and with engine stopped pull a dipstick checking the ATF level. So much easier and no OBDII reader for specific ATF temperature required.

My old gas ‘19 RAV4 was odd like that too. I think I was supposed to warm the fluid up and then check the level after turning the engine off. It didn’t have a dipstick though. It had this weird straw sticking up into the transmission as part of the drain plug. fluid above the straw was too high a level and pours out of the drain plug.

My newer hybrid ‘21 RAV4 is so much simpler. Literately drain and fill it like a differential. When fluid starts dropping out of the fill hole with the car level, you’re at the right ATF level.

 

[yrwei52]

⋯
7) Use a loooong funnel to replenish the same amount that was drained out

IMO this statement could be problematic and misguided as many members had verified that the factory fill in the automatic transmission most likely is under-filled; just like the rear differential. See my previous post, post #105.

Always use some good OBDII reader to verify the ATF temperature which is at 122°F / 50°C, and check the ATF level with engine idling.

 

[dodgerfan356]

Yes, Mazda really made it so difficult to check the ATF level.

View attachment 320330
View attachment 320331
The step 6 in the Mazda Workshop Manual specifically says “while leaving the enginf idling” when you take the measurement of the ATF level at 122°F. I also would shift transmission into every gear then measure the ATF level with the engine idling. When engine is idling, the AFT pump is functioning and circulating the ATF everywhere in the transmission including the torque converter which has a half of the total ATF quantity. That’ll bring down the ATF level in the pan significantly. It’s similar if you check the engine oil level with the engine running, the oil level will be much lower in the oil pan.

Here FerrariF1 originally thought his ATF level from factory was fine with engine stopped on his CX-5 2.5T. Once he rechecked with engine idling, he needed about 600ml (0.635 quart!!!) to bring the ATF level to the Full mark (although the ideal level should be at the middle block area). Mazda under-filled the ATF in his transmission as usual at the factory. That’s why you don’t re-fill the same amount of fresh ATF as drained ATF because the factory fill usually is too low.

He also did an experiment and found the differences on ATF level in different ATF temperatures on his CX-5 with 2.5T:







Honda and Toyota definitely make this easier:

Thanks for posting those instructions!

I'm still a bit iffy on checking the level with engine running without touching something that shouldn't be touched (fan, something hot, etc). Plus if reaching from above, the air box is in the way. Did you check from underneath? What's the best way to get to it?

Edit: I was actually able to angle the airbox up enough that I could get my arm down there and pull the dipstick. Not sure if it was the "right" place to go from, but felt a lot better than crawling under the car! I guess now I need to buy a scanner that can read transmission temp (or see if I can find an app that works with my 10 year old bluetooth scanner). Immediately after starting, probably around 75 deg, it was maybe half a cm below the L line (and that's after putting in 2-3 oz more than I drained out yesterday.

 

[omarh93]

I'm not a mechanic so take my answer with a grain of salt.

I think the big difference is that they want you to check the level when the ATF is within a specific temperature range.

I tend to agree with you -- my plan is to run the engine until the atf gets to the right temp, then turn the car off and quickly remove the airbox to check the fluid level. I think the thing to keep in mind is that the moment you turn the car off, the fluid will start cooling back down which could conceivably affect your reading on the dipstick. But my belief is that it won't cool down instantly, so it should be fine. (If I have to add more fluid then my method will become a PIA...)

So I went ahead and did it today.
I took video that I'll upload on youtube later.
I thought of an alternative way of checking the dipstick but I don't think i'd suggest it to anyone lol.
Basically when the car was running I went underneath and remove the dipstick from the bottom and checked it. I used a temperature laser gun to check the temperature of the transmission fluid pan and I noticed when it was cold the dipstick wasn't seeing hardly anything, but once it warmed up I started seeing oil on the dipstick. so I think if you check it when its cold you'll end up overfilling it that's why you have to check it when its warm.
The issue I had was I really couldn't clearly see where the oil level was on the dipstick the way I was under the car and I finally just got fed up with it and stopped checking.
In my case I carefully measured how much I drained (3.2 quarts) and then refilled it just a little more like 3.3 or 3.4 quarters. I keep hearing people say that mazda underfills these, but the car was running like that for 104k miles and its fine, so I think it'll be ok. Plus I now added about .1 .2 more than I drained. I noticed the new oil is blue and the old was definitely black.

 

[yrwei52]

Thanks for posting those instructions!

I'm still a bit iffy on checking the level with engine running without touching something that shouldn't be touched (fan, something hot, etc). Plus if reaching from above, the air box is in the way. Did you check from underneath? What's the best way to get to it?

Edit: I was actually able to angle the airbox up enough that I could get my arm down there and pull the dipstick. Not sure if it was the "right" place to go from, but felt a lot better than crawling under the car! I guess now I need to buy a scanner that can read transmission temp (or see if I can find an app that works with my 10 year old bluetooth scanner). Immediately after starting, probably around 75 deg, it was maybe half a cm below the L line (and that's after putting in 2-3 oz more than I drained out yesterday.

Anyone who wants to read a true ATF temperature properly should be using a live data scan tool such as Forscan which supports the Mazda TFT parameter (and many live data tools do not).

Guide ATF Drain/Fill

Perhaps do both and see how much they differ? The ATF temp sensor is located inside of the transaxle valve body, so it's just a guess as to how close those three temps would be at the 122ºF target checking point.

Just an FYI that, if you have a Windows laptop, you can get the Forscan live data tool up and running on it for as little as $20. Forscan currently offers a free download of their software for Windows, and you can buy an inexpensive OBD adapter to read TFT (and a whole lot more as well). The Forscan doc states that they no longer support the lower-priced adapters, however they still work just fine for the simple stuff. This is a very easy and inexpensive way to get TFT the way the manual says to do it. But as always, your vehicle your choice.

Read the subsequent posts in above thread by edmaz for more details on Forscan.

Yes, doing the ATF level check from top should be easier. Trying to sway away the whole air box, with or without the bottom part, and keep the air flow sensor wires connected, should be the way to go IMO.

 

[yrwei52]

So I went ahead and did it today.
I took video that I'll upload on youtube later.
I thought of an alternative way of checking the dipstick but I don't think i'd suggest it to anyone lol.
Basically when the car was running I went underneath and remove the dipstick from the bottom and checked it. I used a temperature laser gun to check the temperature of the transmission fluid pan and I noticed when it was cold the dipstick wasn't seeing hardly anything, but once it warmed up I started seeing oil on the dipstick. so I think if you check it when its cold you'll end up overfilling it that's why you have to check it when its warm.
The issue I had was I really couldn't clearly see where the oil level was on the dipstick the way I was under the car and I finally just got fed up with it and stopped checking.
In my case I carefully measured how much I drained (3.2 quarts) and then refilled it just a little more like 3.3 or 3.4 quarters. I keep hearing people say that mazda underfills these, but the car was running like that for 104k miles and its fine, so I think it'll be ok. Plus I now added about .1 .2 more than I drained. I noticed the new oil is blue and the old was definitely black.

I have posted the report above by FerrariF1 showing how sensitive to the volume the ATF is on the dipstick with different temperatures. Your observation is consistent with that. But now you should have know Mazda had under-filled your ATF from factory.

Based on many reports, people usually need 3.75 quarts for an ATF drain-and-fill for older version of SkyActiv-Drive automatic transmission. But on the 2.5T you may need a bit more as the total ATF capacity on transmission has increased a bit.

Checking the ATF level from top side with the air box swayed away like my previous post mentioned with a live data ATF temperature reader certainly seems to be a better way. With engine running, be careful the radiator and AC fan which could be running suddenly. Although you felt running low on ATF in your transmission for 104K miles seemed to be fine so far, I’d believe topping off your ATF to the proper level at your earliest convenience is essential, unless you plan to do 2 more drain-and-fills making the fresh ATF content near 90%.

 

[omarh93]

If anyone wants a good laugh, I took video of some of it....

2017 Mazda CX9 ATF Transmission Fluid drain and fill

I couldn't find many videos showing someone draining and filling the transmission fluid for a 2017 CX9 so I decided to make my own.I don't normally make car ...

www.youtube.com

 

[omarh93]

I have posted the report above by FerrariF1 showing how sensitive to the volume the ATF is on the dipstick with different temperatures. Your observation is consistent with that. But now you should have know Mazda had under-filled your ATF from factory.

Based on many reports, people usually need 3.75 quarts for an ATF drain-and-fill for older version of SkyActiv-Drive automatic transmission. But on the 2.5T you may need a bit more as the total ATF capacity on transmission has increased a bit.

Checking the ATF level from top side with the air box swayed away like my previous post mentioned with a live data ATF temperature reader certainly seems to be a better way. With engine running, be careful the radiator and AC fan which could be running suddenly. Although you felt running low on ATF in your transmission for 104K miles seemed to be fine so far, I’d believe topping off your ATF to the proper level at your earliest convenience is essential, unless you plan to do 2 more drain-and-fills making the fresh ATF content near 90%.

Can you check the video I posted. I show what the dipstick looked like when I the temp of the pan was at 122. does it look right? or still low?

 

[yrwei52]

Can you check the video I posted. I show what the dipstick looked like when I the temp of the pan was at 122. does it look right? or still low?

Thanks for making a video. Based on your video at 24:50 mark, and this’s the screen shot, your ATF level is too low if you took the measurement with the dipstick full seated.

Compare yours to FerrariF1’s. He added 600 ml / 0.634 quart Mazda ATF FZ to the factory fill; which took the ATF level to the upper / full mark at 51°C / 123°F. The ideal ATF level is at the middle block mark of the dipstick at 122°F.

For ATF temperature, the best is to read the live data from the built-in ATF temperature sensor with a capable OBDII reader, although using a thermal gun is better than nothing.

 

[omarh93]

Thanks for making a video. Based on your video at 24:50 mark, and this’s the screen shot, your ATF level is too low if you took the measurement with the dipstick full seated.

View attachment 320367

Compare yours to FerrariF1’s. He added 600 ml / 0.634 quart Mazda ATF FZ to the factory fill; which took the ATF level to the upper / full mark at 51°C / 123°F. The ideal ATF level is at the middle block mark of the dipstick at 122°F.

View attachment 320368

For ATF temperature, the best is to read the live data from the built-in ATF temperature sensor with a capable OBDII reader, although using a thermal gun is better than nothing.

Thanks for looking. I think you're right. Maybe I'll just remove the intake again, and add another 0.2 or 0.3 quarts and call it a day. Not sure I have the patience to go back under and check the dipstick again and I can't seem to get to it with the intake still connected either...

 

[yrwei52]

Thanks for looking. I think you're right. Maybe I'll just remove the intake again, and add another 0.2 or 0.3 quarts and call it a day. Not sure I have the patience to go back under and check the dipstick again and I can't seem to get to it with the intake still connected either...

IMO, going from the top side should be a better way to do this. Many had done that including OP and dodgerfan356 in post #107. I understand your 2.5T has more turbo plumbings then the 2.5L NA, but your CX-9 also has a bit bigger engine bay space then a CX-5. I believe you should be able to remove the entire air box then sway it away with air hose and wires connected may be without the bottom part of the air box. You can PM dodgerfan356 for some detailed instructions or photos how to access the dipstick from the top side as he just did it that way on his CX-9.

My another suggestion is since you’re going to go through the same process again to add some more ATF, and you can only drain the ATF for about a half of the total capacity, may be you should get another 5 ~ 6 bottles of Mazda ATF FZ with a new drain plug washer and do a second drain-and-fill after you drove your CX-9 for several hundred miles. Thus you‘d have about 75% of fresh ATF in your transmission which is better than your current 50%. Many do 3X drain-and-fills to get about 87.5% fresh ATF and call it a day.

If you really just want to top off your ATF, my estimation is you need about 0.3 ~ 0.5 quart, depending how much you’d refilled. For a gen-1 CX-5 from Kedis82ZE8’s report we usually need about 3.72 quarts to refill for a simple drain-and-fill, while the first drain from the factory fill is only 3.4 quarts. This means the factory fill is 0.32 quart too short.

Transmission fluid change without filter replacement

The total ATF capacity on automatic transmission for the 2.5T is slightly larger than the capacity on transmission for the gen-1 CX-5. So YMMV.

 

[dodgerfan356]

Just checked mine at 50 deg C and it was exactly on the low line (after having added back what I drained out). Added just under 0.25 quarts and I think it's just about right, so mine was borderline underfilled from the factory as well. I'm thinking about upgrading my 2016 to a 2023 CX-9...I guess transmission fluid level will be one of my first checks after purchasing!

 

[bernardmind]

Just want to add this information here:
It takes about 17mins to reach 122F on cold start idle and about 5 mins while driving

Cold start idle
https://youtu.be/N7vfZ3WOOOQ?si=-MHVhZTFmN1AjqIv

Cold start driving
https://www.youtube.com/shorts/2rgLxxe3Us8