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2004 Focus Wagon, Zetec DOHC, Auto
1,590 Posts
Discussion Starter #1 (Edited)
I was looking for an easier, faster, and cleaner way to change my transmission fluid without dropping the pan, so I decided to install an external spin-on filter and magnet. The additional filtering capability is a bonus. This is what I did:

The Filter Mount:
I used a Derale 13049 kit purchased through eBay from JEGS. Derale makes several filter mounts (e.g. 25750, 25751, 25728, etc.) that should work depending on where you choose to mount it. I picked the 13049 because it has four ports and therefore offers the greatest flexibility of mounting choices for running hoses left or right, or left and right. You can also use the extra two ports for installing a temperature gauge on the outlet side, and/or a pressure gauge on the inlet side. The pressure gauge could be used to monitor backpressure. If the backpressure increases with use, then the filter is getting clogged. The other reason I chose the 4-port mount was because I might sell the car at some point and remove the kit for use on another vehicle and the hoses might need to be arranged differently. The 2-port versions are a little cheaper.

To begin installation, use the mount to draw a template on a piece of paper. I chose to install it on the frame just ahead of the driver’s side front tire. After you have located the desired installation point, tape the template to the area.

Drill the holes using a right-angle adapter on your drill. Make a 1/8” pilot hole followed by a 3/16” bit. Put Teflon tape on the plugs and hose barb fittings. Install them in the mount (do this while holding it in your hands…don’t use a vise because you can break the mount if you overtighten). Do not put Teflon tape on the filter nipple (see the additional note about installing the nipple below). Now install the mount with the three screws provided in the kit. It is easiest to put the top screw in first because you can use a ratchet. The bottom two screws require a wrench. Leave the first two screws slightly loose until you get the third screw in. I put a washer under one corner to act as a spacer because the frame curved in this area.

The Filter:
I used a Purolator L25230 because I had them on hand. I used those as my engine oil filter until I switched to the larger FL-1A. I placed two hard drive magnets at the inlet. The magnets will catch the ferrous debris from the transmission that might otherwise make it through the filter media. Ferrous debris is 50 to 80 percent (depending on who you ask) of all the debris in an automatic transmission.

The magnets fit nicely in the filter mount because the area between the oil filter and the base of the filter nipple is recessed into the mount. These particular hard drive magnets are about 1.5” long X .6” wide X .1” thick and come from a desktop hard drive. Laptop hard drives have much smaller magnets. When the filter is screwed on they contact the mount and flatten out to become parallel with it. They do not interfere with fluid flow and do not block the holes in the filter. If you use a larger filter it would probably be easier to place them onto the mount before screwing the filter on…just let them adhere to the filter nipple while parallel with the filter mounting surface.

The Hoses:
Disconnect the return hose (the lower one) from the transmission cooler and also unscrew it from the transmission. Use a 19mm wrench to hold the brass fitting on the transmission while turning the hose nut with a 17mm wrench. After you get the return line off the car, cut off the clamp and remove the rubber hose part. Reinstall the aluminum portion of the return line and leave it loose for now so that you can get the optimal position for the new rubber hose.

Install new rubber transmission hoses between the hose barb fittings on the filter mount and the transmission return line and the transmission cooler. Be sure not to get the hoses backwards…fluid flows from the lower cooler line outlet to the transmission. Now tighten the return hose at the transmission. Do not make any bends in the hoses that have less than a 2” radius and keep them away from any sharp edges or wear points.

I used Gates 3/8" Transmission Oil Cooler Hose (Part # 27061). Clamp the hoses with either stainless worm screw clamps or spring clamps leaving at least 1/8” of the hose end exposed. I didn’t reuse the OEM spring clamp because it didn’t seem to fit tightly. If the hose easily twists after clamping, then it is probably not tight enough. Keep an eye on these connections for a while just in case there is any seepage.

If you are doing a fluid flush at this time, don’t connect the hose from the cooler to the filter mount yet so that you can use it for doing the flush.

Prefill the filter with fluid and lube the gasket, then screw it on. Tighten the filter by hand with ½ to ¾ turn after gasket contact with the mount. Now you are ready to test for leaks. After the tranny is warm, top off the fluid…you shouldn’t need much if you prefilled the filter.

The Internal Transmission Filter and Magnet:
This is the internal transmission filter. The filter media is about 4” X 5” and is double-sided for a total area of roughly 40 sq. inches. The pleated spin-on filters will have 4 times or more (depending on which one you choose) surface area than the internal filter. The internal transmission filter is capable of filtering down to only about 100 microns and is better described as a screen than a filter. The external spin-on filter is capable of filtering out particles 1/5 that size. The internal filter and pan magnet are meant to capture debris in the fluid; however neither can capture the sub 100 micron non-ferrous particles (clutch particles, aluminum, brass, copper, etc.) that float around inside our transmissions. In theory, the internal filter should never get much of anything in it again because the spin-on will catch much smaller particles than it is capable of doing. Less floating debris means a brighter future for the tranny.

Debris in the filter prior to installing the spin-on filter consists of mostly metal and plastic bits that I can identify. Unfortunately the photo does not show everything that I can see on it with my eyes.

The internal transmission pan magnet prior to installing the spin-on filter – gross!

A Spin-on Magnet:
This is an alternative spin-on magnet that would replace the hard drive magnets shown above. My understanding is that these cannot be cleaned.
Example installation:

Alternative Inline Filter with a Magnet:
As an alternative to a spin-on filter, this is an inline filter that could be placed in the return line. It includes a magnet. I use these on my Honda to replace the OEM inline filter.

The photo below contrasts the physical sizes of the spin-on filter, the Magnefine® inline filter, and the Honda 25430-PLR-003 inline filter. Basically there is no contest here as the spin-on is clearly much larger. Honda considers their inline filter to be “lifetime” (whatever that means) and it is not even mentioned in the owner’s manual as a service item. The spin-on filter might be a true lifetime filter if you periodically check the backpressure to make sure it is not loading and clean the magnets. I plan on changing the filter regardless.

When to Install the Spin-on Filter:
You can install the external spin-on filter at any time. It will immediately arrest further deposits on the internal filter. Ideally, the spin-on filter would be added along with a complete fluid change and new internal filter. If you have less than about 15,000 miles on your tranny since the last fluid and filter change, there is probably no need to do it again before installing the spin-on filter.

How to do a Fluid Change with a Spin-on Filter:
1. Park the car on a level surface and set the e-brake. There is no need to jack the car up and crawl under it.
2. Remove the spin-on filter and cut off the closed end to remove the filter media. This is a good time to examine the filter media to see what is being captured.
3. Reinstall the filter (now just a can) onto the mount. This will direct the fluid flow downward.
4. Cut the bottom off of a 2 liter soft drink bottle and place it upside down on the top of a 1 gallon (or more) clear plastic jug with calibration marks on it. You can “calibrate” the large jug using water and your wife’s measuring cups if she doesn’t catch you doing it.
5. Slip the soft drink bottle over the filter to act as a funnel with the larger jug under it. You can also sit this inside a pan just in case of an overflow.
6. Start the car –IDLE ONLY—and pump 3.17 quarts (3.0 liters) into the catch jug, then stop the engine.
7. Pour new fluid through the dipstick into the transmission equal to what was removed in the previous step.
8. Repeat steps 6 & 7 one more time for a total of 6.34 quarts (6.0 liters) removed at this point.
9. Start the car –IDLE ONLY—and pump 1.5 quarts (1.4 liters) into the catch jug, then stop the engine.
10. Pour new fluid through the dipstick into the transmission equal to what was removed in the previous step.
11. Prefill a new spin-on filter and install it. Don’t forget the magnets.
12. Start the car and check for leaks. Drive the car until tranny is warmed and then check fluid level at idle in Park.
13. If somehow you overfilled the tranny, just unscrew the spin-on filter and pour the extra back into one of your bottles.

If you have done this correctly, then about 7.5 - 8 quarts should do a complete flush and fill (excluding the spin-on filter). Total system capacity is 7 quarts, so the extra amount is just for good measure. An alternative fluid service would be doing steps 6 & 7 at every engine oil change.

If you have a helper and a large enough catch jug (2 gallons or more), then this can be done without stopping the car…just quickly pour new fluid into the dipstick AFTER the initial 3.17 quarts (3.0 liters) has been dispensed into the jug. Stop the engine at the 7.5 - 8 quart (7 liter) mark. Optionally, while you are pouring the new fluid into the tranny, the helper can also shift slowly back and forth between all the gears while holding the brake to get a little more of the old fluid out.

Here is a photo of my catch jug in place over the filter (of course the end is not cut off the filter here).

Additional Notes:
1. The internal transmission filter and pan magnet remain in place.
2. Complete filter kits with hoses and filter are available. However, I do not know if the hard drive magnets will fit in another brand of mount. Make sure you get 3/8” hose to fit the Focus.
3. A larger filter such as the FL1-A can be used instead of the L25230 (Ford FL-400S). The FL-1A would add about 1 additional quart to the total system fluid capacity. Kits such as the Perma-Cool® 10678 and others use a PH8A/FL-1A filter.
The specifications for the FL1-A Filter:
Height (in) 5.190 in.
Outside Diameter (in) 3.780 in.
Relief Valve Open (psi) 11-14 psi
Anti-Drainback Valve Yes
Smallest Particle Filtered 20 microns
Maximum Burst Pressure (psi) 200 psi
Thread Size 3/4-16 in.
Gasket Outside Diameter (in) 2.800 in.
Gasket Inside Diameter (in) 2.422 in.
Gasket Thickness (in) 0.203 in.
4. The use of a “performance” filter such as a PureOne® may provide added filtering benefits, but they may also add additional backpressure. However, those filters usually have more pleats and more surface area, so there may be no backpressure increase. This would need to be tested.
5. If you are concerned about the magnets interfering with fluid flow, test backpressure with and without the magnets to confirm they are okay to use.
6. Buy a quality filter because it will probably be on the car for 30,000 miles or more. Don’t use any filter with cardboard in them or those that say “Made in China”. Just my 2 cents on that!
7. This setup is does not hang below the bumper/fender and cannot be seen without looking under the car.
8. You can install a drain plug in the transmission pan, but I think by using this setup you don’t need one.
9. Before installing the spin-on filter, I measured 2 psi in the return line in neutral at idle by attaching a pressure gauge at the outlet of the transmission cooler. Revving the engine to about 3500 rpm resulted in about 3 psi. The low pressures are to be expected in this hose because the other end is open and just dumps into the transmission. After installing the filter, I measured 6 psi at idle and 7 psi at 3500 rpm. The additional hose length probably accounts for about 1 psi, so the filter has about 3 psi drop across it; very low in my opinion. In gear the pressure might be higher and I may test that someday.
10. I bought 5 feet of SAE J1019 hose. I used 4 feet for the lines and then I used a few more inches to attach a pressure gauge temporarily in place using a Tee fitting. A 0-30 psi gauge for checking backpressure can be bought on eBay for $15 or less and can be installed permanently on the filter mount’s extra inlet port.
11. If you look carefully at the third photo, you will notice that there are holes drilled through the threaded filter nipple. I did this so that I could insert a nail and then use it to screw in the nipple by hand (I didn’t want to mark up the threads by using pliers). If you drill this hole, be sure to deburr it so that nothing ends up in the tranny.
12. The filter can be removed periodically (such as at every engine oil change) for cleaning the magnets if you desire.

And finally, this is what your transmission oil should look like when it is clean…..

…..and that, my friends, is what it’s all about!
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