Crankcase Breather Filter
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Crankcase Breather Filter
I was looking up parts for my 94 Bronco 5.0 today and notcied there's a crankcase breather filter. I tried looking for it under my hood but I can't find it. I saw a parts diagram that showed it in the lower half of the air box. I opened up my air box and it's not there. There are no hoses or anything attached to my air box for this filter. Would it be located somewhere else? Did some models not have them?
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I did a little more searching and apparently trucks with a mass airflow sensor don't have the filter. My truck has a MAF, so I guess that explains it. Did they change to a MAF system mid-year or something?
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The crankcase breather is to let filtered air in so that the PCV does not create a vacuum. Mass-air doesn't have anything to do with it. Is there a hose fitting coming off the side of the oil-filler tube in the driver's side valve cover?
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Umm, did you read my first post at all? I did exactly that. There is no breather filter underneath the engine air filter.
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I don't remember. I can't look under the hood right because I'm at work. I'll check either later today or tomorrow.
Lead Driver
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From: Gateway to the West
There should be a PCV breather filter under the air filter in the box... Doesn't mean there is one on your truck but it also doesn't mean it shouldn't be there for the very reason citied by jas88. Any PCV valve left open to the air is missing the plumbing back to the air filter box after about 1985. Why is this true? Because EPA regulations mandated it. "Breather filters" could no longer vent to the outside air. Blow-by gasses had to be recovered into the intake and run through the combustion cycle to neutralize any pollutants that could be burned off.
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I'll try to get some pictures of the air box when I get a chance. There aren't even any holes in it for the filter to plug into. The box apparently was designed to not a have a filter in it in the first place. I recently bought the truck from the original owners who bought it brand new (my future in-laws) They're not exactly into modding vehicles. They wouldn't even know the difference between an oil filter and a fuel pump. So I highly doubt they tampered with the breather system.
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Ok, then I will ask this: Where does the line from the barb on the black plastic cap in the driver's side valve cover (aft of the oil fill port) terminate? That's the line that should be running to the breather filter in the lower aft wall of the air filter box. I am curious to know where it terminates.
My first thought was that MAF vehicles might have had it moved further up the line in the intake plumbing since oil particles will ruin MAF sensors. (Which is why you will kill MAF sensors if you run K & N's oil-inpregnated filter systems downstream of them). The only fly in that ointment is the fact that the breather filter is DOWNSTREAM of the primary air filter so the chances of oil getting through the breather AND the main air filter are slim to none so there would have been no need to relocate it for MAF vehicles.
My first thought was that MAF vehicles might have had it moved further up the line in the intake plumbing since oil particles will ruin MAF sensors. (Which is why you will kill MAF sensors if you run K & N's oil-inpregnated filter systems downstream of them). The only fly in that ointment is the fact that the breather filter is DOWNSTREAM of the primary air filter so the chances of oil getting through the breather AND the main air filter are slim to none so there would have been no need to relocate it for MAF vehicles.
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OK, so I finally got around to taking some pics. Please excuse the dirt/former mouse nest in the airbox; I will clean that shortly.
There is a breather hose that goes from the air intake tube (close to the throttle body) to the valve cover, right underneath the oil cap.
There is a breather hose that goes from the air intake tube (close to the throttle body) to the valve cover, right underneath the oil cap.
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From: Imperial, MO
I'm late to the party, but OP, your system will not have a breather filter. The PCV system pulls filtered, metered air from the intake tube downstream of the MAF and air filter. The air passes through the crankcase, exits the passenger side valvecover via the PCV valve, and enters the upper intake manifold.
The speed density trucks have the breather filter in the air filter box, upstream of the engine air filter. That placement would create a unmetered air leak with a MAF arrangement.
The speed density trucks have the breather filter in the air filter box, upstream of the engine air filter. That placement would create a unmetered air leak with a MAF arrangement.
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Ah, so I was right that the MAF trucks don't have the filter. So, the PCV valve is on the passenger side valve cover eh? I was looking for it last night but couldn't find that either. It was dark out though. I will take a closer look today.
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