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What's this filter called?

Hopefully an easy question this time…I replaced the air filter on my 1991 F150, and there’s another little filter underneath it. I think I see what it does…there’s a line from that filter to the valve cover just below where you add oil…looks like it’s a pressure relief valve for the engine. Ok, so this filter is pretty oily and looks like it should be replaced, but I don’t know what it’s called and therefore haven’t been able to find a new one online! I’ve been googling for awhile now and just can’t find the sucker. If anyone could give me the name of this part, I’d be grateful!

That’s the crankcase breather filter.



It should be dry, not soaked with oil…Check your PCV system, the valve, it’s connection hoses and the vacuum port the hose connects to. If any of this gets plugged up, crankcase vapors have no place to go but up into your air-cleaner through that little filter…

I used to know that name, not feeling bad I could not think of it, but old technology is getting slowly added to the internet, Thinking how easy it will be for kids in the future to get genealogy info pictures etc., vs visiting various cities and looking through old books and microfische.

It’s also called a breather element. I agree with the others who recommend checking the PCV system. Air is supposed to flow from the air cleaner housing through the breather element to the the valve cover, not the reverse.

The pcv path on my Ford truck starts at the air cleaner, then to the valve cover on one side, then through the crankcase to the valve cover on the other side, up through the pcv valve, and via a thick hose to the intake manifold. If you temporarily pull the pcv valve from the valve cover (with its hose to the intake manifold remaining attached), with the engine running you should feel some suction at the open end of the pcv valve. If you don’t, the pcv valve is probably shot.