# Crankcase breather filters



## mitchell35758 (Oct 21, 2005)

Can adding a filter to the crankcase breather line cause problems down the road? I had read an article about this a while back and can't remeber what exactly it said and I can't find it on the internet to find the answer to my question.


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## jerryp58 (Jan 6, 2005)

mitchell35758 said:


> Can adding a filter to the crankcase breather line cause problems down the road? I had read an article about this a while back and can't remeber what exactly it said and I can't find it on the internet to find the answer to my question.


Well, if you're talking about the PCV, we're supposed to already have a filter in the airbox. I've cleaned my air filter twice and haven't noticed it; but I haven't really thought to look either  They don't have a picture in my service manual, but they say it's in the airbox. The one's I've seen in previous cars were white and reminded me of a cross between styrofoam and a sponge. Let me know if you find it and what condition you find it in. I really need to take a look around that engine compartment someday.


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## mitchell35758 (Oct 21, 2005)

jerryp58 said:


> Well, if you're talking about the PCV, we're supposed to already have a filter in the airbox. I've cleaned my air filter twice and haven't noticed it; but I haven't really thought to look either  They don't have a picture in my service manual, but they say it's in the airbox. The one's I've seen in previous cars were white and reminded me of a cross between styrofoam and a sponge. Let me know if you find it and what condition you find it in. I really need to take a look around that engine compartment someday.


Hey jerry
Take a look at the upper rear portion of the air filter box cover. 

Mine looked a little on the dirty side with 26000miles. I can't compare it to others that I have owned so I can't say if it is in bad shape or not. I seriously doubt it is though.


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## jerryp58 (Jan 6, 2005)

mitchell35758 said:


> Hey jerry
> Take a look at the upper rear portion of the air filter box cover.
> 
> Mine looked a little on the dirty side with 26000miles. I can't compare it to others that I have owned so I can't say if it is in bad shape or not. I seriously doubt it is though.


I'll be looking in there in the next 2K miles to check out the air filter. So, is that the filter you were thinking you needed to add (the original post)?


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## mitchell35758 (Oct 21, 2005)

jerryp58 said:


> I'll be looking in there in the next 2K miles to check out the air filter. So, is that the filter you were thinking you needed to add (the original post)?


Well, yes and no. The aftermarket intake does not provide a place for that filter. I was thinking about installing a mini conical breather filter. Was reading that in doing so, you don't have the suction to pull the oily air out, it just pushes itself out on its own and SUPPOSDLY(don't know for sure) could eventually cause a build up of oily residue. Don't know how true this is. Just curious. I also heard that allowing the "oily air" from the crankcase can cut down on the octane level of the gas. I am sure that it is not by much, but again just curious as to what I think I should do.


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## NismoFrontin' (Oct 4, 2005)

mitchell35758 said:


> Can adding a filter to the crankcase breather line cause problems down the road? I had read an article about this a while back and can't remeber what exactly it said and I can't find it on the internet to find the answer to my question.


No problems here. I think it helped my performance because all that hot air isn't going into my cold air intake anymore.


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## mitchell35758 (Oct 21, 2005)

NismoFrontin' said:


> No problems here. I think it helped my performance because all that hot air isn't going into my cold air intake anymore.


I think I am going to go with the filter because the intake doesn't have a filter inside of it as does the OEM air box.
From your picture, it looks like you are using a K&N breather filter, right? I had bought a cheap one from autozone the day I placed my order for my intake just to be ready once everything got here. I think I am going to return this filter because it looks like cheap quality. The instructions on my intake say to clean the intake filter every three thousand miles. So when that interval is up I am going to buy the K&N filter for the intake and at the same time just get and install a K&N breather filter.


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## azrocketman (Oct 5, 2005)

mitchell35758 said:


> Well, yes and no. The aftermarket intake does not provide a place for that filter. I was thinking about installing a mini conical breather filter. Was reading that in doing so, you don't have the suction to pull the oily air out, it just pushes itself out on its own and SUPPOSDLY(don't know for sure) could eventually cause a build up of oily residue. Don't know how true this is. Just curious. I also heard that allowing the "oily air" from the crankcase can cut down on the octane level of the gas. I am sure that it is not by much, but again just curious as to what I think I should do.


1) The crankcase has positive pressure due to blowby of combustion gasses past the piston rings. No suction is required to vent the pressure. In fact, if you totally sealed the crankcase the pressure may be sufficient to pust oil out of the dipstick tube.

2) Older engines (pre 1963 in California, pre 1966 for the feds) just used a "road draft" tube to vent the crankcase. All those unburned hydrocarbons just went into the air. The PCV valve was the attempt to close the system.

3) Many "hot rodded" older engines put vent filters on the valve covers. Oily residues accumulated around these vents. You get oily residue because the pressure in the crankcase is forcing out oil and combustion vapors.

4) The only explanation I can have for the "oily air" cutting down the fuel octane is that it slightly richens the fuel mixture making detonation a little less likely. The only purposes of the crankase ventilation system is to reduce crankcase pressure and burn crankcase vapors. The only purpose for filters in the system is to keep dirt out of the crankcase.


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## mitchell35758 (Oct 21, 2005)

azrocketman said:


> 1) The crankcase has positive pressure due to blowby of combustion gasses past the piston rings. No suction is required to vent the pressure. In fact, if you totally sealed the crankcase the pressure may be sufficient to pust oil out of the dipstick tube.
> 
> 2) Older engines (pre 1963 in California, pre 1966 for the feds) just used a "road draft" tube to vent the crankcase. All those unburned hydrocarbons just went into the air. The PCV valve was the attempt to close the system.
> 
> ...


Hey thanks man. 
Some of this was in that article that I can't find. That was the key info I was looking for about the pressure being sufficient enough to not require suction from the intake. Thanks again :thumbup:


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