Thread: Non genuine air filters not sealing

Following on from Ben's treatise on air filters - see Air Filter Tests (Finally) - I'd like to suggeast that it doesn't matter what filter material you have if the filter box leaks past the seals.

Last week I had the opportunity to look inside the top of a forum member's engine and, consequently, inside his air filter, MAF sensor, air duct, and throttle body.

To be frank I was shocked!

What happened was that when I walked past the car I looked into the engine bay and noticed brown "muddy" residue on the ram tubes in the upper manifold. Then I looked inside the plenum chamber and wiped my fingers through a thick layer of more "mud". That prompted a comment or three so I was shown the MAF sensor which was liberally coated in dust. The throttle body was the same and there was a layer of grime around the butterfly.

I grabbed the filter element and the top of the filter housing and fitted it. The later P38A airbox (not like mine) is, apparently, the same as the D2. The lid (unlike my early model) has only two clips to hold it down. It was apparent that dust was leaking past the filter seal near the outlet on the lid of the airbox. It seems the box was originally designed to have a clip at that location but the clip was not fitted in production models.

The moral of the story? Well, if you have a D2 and do a lot of dusty road work, then you need to closely monitor the air filter. Yours may also be passing a lot of dust. If you have a P38A, you could revert to the earlier airboxc or fit the older cylindrical filter (which mine now has - see 4.0/4.6/P38A Air Box Replacement).

Thanks Andrew, I missed this thread. I've moved my post (and yours) across.