How to: Install Transmission Cooler & Flush 8 quarts of ATF. - Mazda3 Forums : The #1 Mazda 3 Forum
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post #1 of 239 (permalink) Old 01-08-2007, 03:34 AM Thread Starter
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How to: Install Transmission Cooler & Flush 8 quarts of ATF.

[size=12pt]How to perform an 8 quart ATF Flush on a 2006 Mazda3 2.3L Sedan[/size]

READ FIRST: A number of people are asking me where they can buy a transmission fluid pump. Well the answer is YOU ALREADY HAVE ONE... It's installed in your car and all you have to do is start your engine (in park) and the pump will automatically cycle automatic transmission fluid through the OEM transmission cooler. To take advantage of this, all you have to do is disconnect the "output" fluid hose that connects to the existing OEM cooler, and then you attach a clear vinyl tube to the "output" nipple. Then start your car and your car will AUTOMATICALLY spew old atx fluid out of the clear vinyl tube and into a container. Once the old fluid has come out, you replenish the fluid via the ATX fluid dipstick. Remember not to let the transmission pump ALL of your ATX fluid out of your car and to stop once it's pumped about 3 quarts of fluid out. Then replace that 3 quarts and do it again to avoid getting air trapped in the system.

OUTLINE (per Bombsquad):

1. Drain old fluid from pan (~3-3.5 quarts)
2. (optional) drop pan and clean circle magnet and replace filter if necessary
3. (optional) replace pan with new high temp silicone gasket maker
4. Refill with new fluid through dipstick hole
5. Attach clear tube to outlet of your atx fluid cooling block into collection bucket
6. Pump out 3 quarts of old fluid by putting car in drive with e-brake and regular brake on
7. Refill with new fluid through dipstick hole
8. Repeat Steps 6-7 until fluid coming out of clear tube is red and bright. (or the same color of your new M-V compatible fluid)
9. Top off the fluid level, test drive, check for leaks, re-check fluid level after fluid is warmed up and top off if necessary.


Basic Metric Socket set and pliers to remove clips that hold on transmission line. (Look up the oil change "how to" in order to remove the black skid plate, and battery covers)
Metric Hex to remove transmission pan drain bolt. (It's either 6mm or 8mm)
6-8 feet of 3/8" I.D. clear tubing available at Home Depot for ~$6. (Get a clamp too) (My writeup suggest 5/16" I.D., but this is very tight and will need a little stretching and some oil as lube to get it to fit)
Container or low profile catch basin to catch old transmission fluid and tape to secure the tube so it doesn't move when draining.
Funnel that fits in the ATF dipstick to put fluid in. Get one that u can shove in there so you don't have to hold the funnel while you pour. (When pouring, do this slowly or else it will burble and splash ATF fluid all over the engine bay.)
8-9 quarts of ATF Mazda M-V or compatible. - I personally use Mobil 1 ATF (full synthetic). If this wasn't in stock, I'd get Mazda M-V Fluid due to the latest TSB bulletin that does not recommend Mercon V to be used as a substitute for Mazda M-V fluid. (Mazda M-V is to be used in the Mazda3).

For informational purposes: The OEM fluid for 5-speeds is Motorcraft Mazda V (M-V) or Ford FNR5, for 4-speeds it is Mercon V. M-V is available at your local Mazda or Ford dealer while Mercon V is available pretty much everywhere. Your dipstick most likely has an M-V engraved on the tip if you drive a 5-speed ATX. M-V does not stand for Mercon V, it stands for the Mazda-V atf fluid which is ASP17 as opposed to ASP11 (merconV).

Yes you may use Mobile 1 Full Synthetic or Castrol Import Multi-vehicle ATF (that says it's M-V compatible). Personally i've got almost 50K miles on my car and no transmission skips, noises or jerks and I've been using Mobil 1 Synthetic ATF.

Keep putting in fluid until the fluid comes out bright red. You'll want to make sure you save some fluid for the end for topping it off to the "max" fill level.

Transmission filter (if you want to replace this while you drop the pan) To get the filter I suggest you visit your local dealership and order the filter that your car requires. You'll have to give them your VIN, and I believe this to be an easy way to get the right part. Keep in mind that changing your ATF filter is not mandatory and mine looked very clean. I will probably change my filter at 80k miles or more. I do not think that this filter is a regular "Mazda" maintenance item to be replaced on a certain interval.

1. I recommend jacking up car and put front on jack stands, then remove black plastic skid plate. It probably can be done if you drive on ramps, or perhaps flat on the garage if you have not lowered your car. First, drain old transmission fluid by removing the hex bolt in the middle of the black transmission fluid pan and observe color and odor of fluid. If there is a burnt smell and flakes then begin to worry. If it's dark red or brownish and no strange odor then this is normal. If it's pink, then there may be coolant/water mixed with your transmission fluid. Mine is normal, though darker than I'd like it to be after having done a double 3qt flush about 8k miles ago. My car has 23k miles on it right now.

2. (OPTIONAL) Drop the transmission pan by first removing bolts, and then gently prying off pan with wide flat head screw driver or plastic scraper and remove and clean circle magnet. Try not to scratch the metal. Scrape off silicone best you can and replace with high temp silicon gasket maker when you re-install pan (I used permatex high temp silicone RTV sealant/gasket maker). Replace the filter if you bought one, I didn't have one so I didn't and just removed the filter and emptied it. I found NO gunk whatsoever and minimal residue on the magnet. Spread a thin coat of the liquid gasket on the rim of the pan. Once the pan is back and the drain bolt is tightened, re-fill with transmission fluid till it's full on the dip stick. (This is considered the drain and refill since it only does about 3-3.5 quarts at a time)

Keep in mind that there is a higher chance of a leak, the more old silicone you leave on the transmission pan rim. Also, DO NOT leave any harsh solvents or cleaners in the pan or on the filter. This will mix with your ATF fluid and may cause problems.

3. Now locate the OEM transmission oil cooler which is the cylinder shaped cooler next to your transmission. It's maybe the size of a can of tuna and has one inlet and one outlet for oil. Locate the "line out" of the cooler and attach the clear tube to this and run it to a container that can hold a couple gallons of fluid.

4. Remember to have NEW transmission fluid in your car... Set your parking brake firm, depress the brake (Hold the brake) and then safely start your engine and put the car into drive. This will allow fluid to flow through your torque converter (at least on most cars). The old fluid will be gushing out of the clear tube and into the catch pan. If it's not, then maybe you chose the wrong outlet on the OEM transmission cooler. DO this until 3 quarts have emptied into the container and stop your engine. I eyeballed it, but you can mark the container with tape at the 3 quart line. Refill the drain pan via the dip stick tube again. Turn your engine on and wait until it fills a couple more quarts and your fluid turns RED again easily visible through the clear tube. Your last 3 quarts are reserved to fill up the drain pan.

5. Re-install transmission line, (recommended to replace the clamp, or at least put the old clamp in its original position when reinstalling the oil line) Put everything back together and you're good to go.

So by starting your engine, your OEM ATX fluid pump will automatically be pumping fluid through your OEM ATX cooler. So by letting this pump fluid OUT of your car, it will be taking fluid from the transmission pan/reservoir. So you have to make sure your ATX pan has NEW fluid in it to make sure you're getting almost all of the old fluid out.

Yes this method can be done without taking off the ATX pan, and it will save some time. It just is more of a complete job if u drop the pan and clean it.

EDIT: Take the following link to my SECOND ATX flush after about 15k miles. More pics, and more info:

For another walkthrough more detailed on dropping the transmission pan and changing the ATX filter see this link:

(Though I suggest you use a more material friendly tool and more careful prying methods for removing the pan and gasket material from the atx pan)

UPDATE: - For those wondering what fluid Mazda uses at their dealership for Power steering? Well I went to the dealership and they most likely use Mercon V fluid. So there is no special fluid... just Mercon V they put in our power steering reservoir.

Take the following link for a Power Steering Flush Walkthrough:

Here is a link to the TSB regarding Mazda M-V atx fluid:

[size=12pt]OPTIONAL - How to install an auxillary transmission oil cooler on a 2006 Mazda3 2.3L Sedan[/size]

This cooler adds a secondary cooling ability to the car with the purpose of pro-longing transmission life, and reducing overall engine temperature. Engine coolant serves the purpose of cooling the transmission fluid in the OEM setup and I believe that a LPD (low pressure drop) cooler can safely and effectively reduce temperatures without decreasing ATF pressure too much. It will also add ATF capacity by approx. 1 quart.

The idea is to run the new cooler AFTER the OEM transmission cooler, then back to the transmission. You have to remove the two front skid plates and maybe your OEM intake. I have a CAI so there was plenty of room for me to work and find the transmission oil inlet on the transmission from the top of the engine. It will be somewhat difficult to find this from the bottom. I used about 4-5 feet of rubber tubing plus the cooler (i discarded the old oil line that goes from the OEM cooler outlet, to the transmission fluid inlet). I tried to not have tubes bend with a curve of more than 3.5" radius. I also protected the tube with the plastic tech flex at the area where it curves around the radiator and secured the flex in place with electric tape.

I'm just going to post my installation pictures. It's pretty straight forward and the cooler is behind the air bag sensor at the bottom of the radiator. It is attached with 2 regular zip ties, and one long "rod" type zip tie that came with the transmission cooler kit.

The tru-cool transmission cooler kit I got was ~$40 shipped from If you want an anodized aluminum fin type cooler, check out the coolers from hotzoneperformance which are $40ea. I chose the least "flow" restrictive cooler. If you want a complete kit with stainless steel lines and instructions then check out the $160 kit at SCI.

For the record, I bought 5 feet of goodyear transmission cooler rubber pipe from Autozone for $1 per foot. (even though my kit came with tube)

Mounted Pictures:

TEST IT: Run the engine top off your ATF fluid since this will increase your fluid capacity. If you bought 8 quarts to flush your ATF, then you'll need an extra quart if you do the cooler too, so that makes 9 quarts total to be on the safe side. (I got 10 quarts of MerconV)

Run your engine, check for leaks, drive it around before you put the two skid plates back.

Warnings and disclaimer! - Hopefully you'll find the best possible routing of the lines and maybe you went with stainless steel lines. I don't want something rubbing on the line to wear through the tube and cause a fluid leak and transmission failure. I take no responsibility for anything that is written on this page so work on your car at your own risk.

Do not overfill your transmission fluid, or underfill.

Reinstall all tubes securely so there are no leaks, route all tubes so that they do not damage anything or become damaged themselves.

Use a Mazda factory manual if you are unsure what does what and "where", etc.

If my transmission fails due to a high pressure drop as a result of my transmission cooler or installation I will let everyone know. This IMO is one risk. Another risk is warranty on your transmission, as well as there is an increased likely hood of leaks due to more connections and tubing to watch out for.


I lubed the tube and inlet/outlet to facilitate sliding the oil tubes over the metal nozzles... Boy is this the PAIN, as is removing them. You'll need gloves, patience, and twisting motion. (don't damage any surround parts please, and don't break anything)


I can't specifiy whether it lowered fluid temperatures or engine temperatures because I have no way of accurately measuring transmission temps.

I put approximately 10,000 miles on this cooler and my fluid still looks red and shifting quality remains consistent. I plan on changing my fluid with a 9qt flush after 20k miles.

The cooler is robust and only minor paint chips in it since the cooler is right behind the front lower grill. There also has never been a leak and my ATX fluid level has been the exact same.

Right after the install, my transmission felt smooth and pretty much the same as before. Perhaps "slightly" less jerky.

The only reason I changed the fluid and added the cooler was to hopefully "prevent" anything bad from happening, prolong transmission, and for diagnostic purposes.

I'll probably edit and revise this as necessary.
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post #2 of 239 (permalink) Old 01-08-2007, 09:06 AM
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

Nice write up! Good info and good pics. Only thing I found was the pic where you labeled fluid in/fluid out, it maybe be labeled backwards since your fluid out hose to your drain pan was hooked to the right side of the pump. Good write up on the cooler too, and your right HEAT is usually the #1 killer of tranny's.
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post #3 of 239 (permalink) Old 01-08-2007, 11:14 AM Thread Starter
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

Alright I'll make that adjustment, and make some revisions.
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post #4 of 239 (permalink) Old 01-08-2007, 02:04 PM
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

How much does a transmission change cost at the dealership or other places? Looks kinda hard to do myself...

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post #5 of 239 (permalink) Old 01-08-2007, 03:42 PM Thread Starter
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

Dealership might charge about $200. You might be able to find a local shop to do it for $100. Just make sure the place that does it won't use solvents or older inferior machine methods to flush.

I spent $3.75x 9 quarts which ended up being $33.75

Then $3 for High Temp Silicone Gasket sealant and $6 for vinyl tube.

$40 shipped for Oil Cooler and $5 for rubber oil tube.

Total cost for DIY transmission fluid flush and Oil cooler installation = $87.75 + 4-6 hours of labor.

I'll probably do another complete flush after 20k miles since it'll only be about $35
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post #6 of 239 (permalink) Old 01-08-2007, 04:44 PM
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

AWESOME JOB! So your pan/filter didn't look anything like that other 4-speed pan/filter in terms of sludge and gunk, that makes me feel better about my tranny.

Great work

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post #7 of 239 (permalink) Old 01-08-2007, 05:02 PM
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

After only 8k miles on that fluid, it sure doesn't look so hot. What kind do you use?

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post #8 of 239 (permalink) Old 01-08-2007, 06:30 PM Thread Starter
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

Last flush I flushed with 3 qts of Penzoil, and finished by adding 3 quarts of mobil 1 atf syn. It wasn't a complete flush the first time hence why I expected this dark brown/red color this time.

This time I'm using almost 90% castrol merconV with 1 quart of mobil 1 synthetic I had leftover.
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post #9 of 239 (permalink) Old 01-09-2007, 02:36 AM
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

Cool! Looks so easy to do your own flush...makes me want to do mine right now. Fluid still looks pretty good and no odd smell from the dipstick. Probably will have to wait until next oil change. I'll be near 30k by then.

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post #10 of 239 (permalink) Old 10-01-2007, 11:59 AM
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Re: How to: Install Transmission Cooler & Flush 8 quarts of ATF.

Nice write up!!!!

Stick Please.....

I go to perform the 8q ATF Flush with regular Mercon V maybe Castrol ...... and install the Oil Cooler with In-Line Filter.......

Them every 5-8k miles ... I go to make a regular 4q ATF Change with a Full Synthetics Stuff...

When i need change the internal ATF Filter...?????

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