Cleaning a BMC CDA air filter.

The following guide was written specifically for the BMC CDA air filter but the basic procedure can be applied to any similar Oil impregnated paper filter.

I would recommend using the manufacturers specific cleaning kit designed for which ever filter you have.

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Right my BMC CDA air filter is way over due a clean, BMC suggest cleaning their filters every 15,500 miles, I think mines done at least 20,000! So here's a basic guide with a couple of extra tips for cylindrical CDA filters that aren't covered in the manufactures basic instructions...


Time to complete whole job: 1 Day.
Actual time fiddling & getting covered in red oil 1-2 hours
.

You'll need the following basic items:

BMC Air filter cleaning cleaning kit, WA250-500 or you can use WA200-500 if cleaning a panel filter.

Philips screw driver.

Roll of strong paper towels.

A bucket, don't use your car washing bucket unless you have some strong degreaser to remove the oil residue that will collect on the sides when cleaning the filter.

Useful but not essential:

A flattened cardboard box to place the filter on.

Rubber gloves.

Step 1: Disassembly.

Remove the air filter from the car & plug opening to throttle body with a clean rag or a stretch a latex glove of the end to stop any crud getting where it shouldn't.

Step 2: Disassembly.

Disassemble filter assembly by removing the four small screws at the bottom (intake side) of the outer-body & pull out the filter element.

Take care with the screws, their small & are easy to round off if you don't use the correct Philips screwdriver.

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Put the screws somewhere safe, I put mine in the cleaning kit box.

Step 3: Tap out the big bits.

Tap the filter gently to dislodge the larger debris that have collected, do not use compressed air as you could damage the paper elements.

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Step 4: Clean it!

Take the bottle of Detergent in your cleaning kit & apply to the filter.
Squirt the fluid down the elements from the outside while holding the filter at an angle over you bucket. You'll start to see the dirt being washed out of the bottom of the filter.

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Don't be tempted to re-ditribute the detergent that's collected in the bucket through the filter again, all you'll do is re-introduce the dirt to the clean side of the filter.

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Once you covered the whole filter & you've used all your detergent leave the filter to stand for ten minutes to allow the detergent to break down the old oil in the filter.

While your waiting you can wash the outer case.

Step 4, Rinsing & repeat.

Rinse out your bucket.
Using another bucket/jug or even a slow running tap/hose and rinse filter until no more debris collects and the bottom of the bucket. Again, don't reuse the contaminated water on the filter.

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Step 5, Drying:

Pat your filter dry and place somewhere with good air flow & allow the filter to dry naturally. Do not use a hair dryer or place in a very warm area as this could damage the paper elements.

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I gave my mine a good 24 hours to dry just to be sure.

Step 6, Oiling the filter:

Here I had a problem, the BMC instructions were for a flat element & call for the filter to be doped on both sides. The CDA filter is a cylindrical design this makes applying the oil a little tricky with the supplied bottle. The other kit comes with an aerosol can of oil & this would make application easier but it would still be very messy & it would not get the oil into all the nooks & crannies.

So I made this up using a small length of cane & some old fuel line from a Nitro RC truck (see, this is why we never throw anything away!)

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This allowed me to evenly distribute the oil around the inside of the filter.

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Once you have applied two coats of oil along the pleats hold the filter the light & ensure the filter is an even red colour. I used about half a bottle of oil the saturate the filter so there's plenty to play with.

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Once your satisfied the filter is evenly coated leave it stand for 30 minutes. I turned mine about quarter of a turn every 5 minutes or so, to ensure the oil didn't collect in one place.

Carefully pat the excess off the filter with paper towels & move on to step 7.

Step 7, Refitting:

Pretty straight forward, rebuild your filter taking care that the screw holes match up, I found mine weren't all exactly in line & the base would line up one way. Fit back in the car. :amuse:

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Nice writeup. I just jetted out my washable filter with a hose and reapplied the oil! Look's like I've been doing it wrong then!
 
I have today cleaned my CDA fitted to my Jaguar XK8 (after 30k miles!) and have a few tips:

1) As well making sure you have the correct Phillips screwdriver it does help if you give the screws a quick blast of Plusgas/WD40 and leave to stand for a few minutes as they are really tight! I am considering changing these screws completely to something with a small nut end, as feel sure that the heads will give up after a while

2) When rinsing after cleaning it took 10x2l jugs of water until it ran clear.

3) After oiling turn the filter to stand on the vanes for a minute then back the other way for 20 seconds, then back to the vanes for a minute. The reason for doing this is you can see the oil trickling down the filter to recoat. The reason for longer on the vane side is that that end will catch the oil, the other way won't and it will run out. You need to repeat this probably 20 times or so and this means you shouldn't need a second coat.

4) The screws do show signs of rust so maybe worth applying a thin coat of rust protectant to the heads.
 
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