Oil in Air Filter Housing - PCV System
#1
09-04-2016, 12:07 PM
Oil in Air Filter Housing - PCV System
Greetings All,
I've got a quick question about the Positive Crankcase Ventilation (PCV) system on our trucks. My '84 F250 (351W, 2bbl) has the original system with a hose between the air cleaner housing and the breather cap on the driver's side valve cover. As long as I've owned the truck (since 1992), I've always found a small amount of oil inside the air cleaner housing. I'm curious what others have experienced.
As I understand it, fresh air is drawn in one direction through this hose, from the air cleaner into the engine and then through the PCV system. The clean air supply is not drawn from inside the air filter itself, but through a separate mesh filter at the edge of the housing.
In theory, air is supposed to go in one direction only, but in my experience sometimes oily air gets blown back. I'm not talking huge amounts, more like a film or just a few drops at most. The engine is old and tired, never having been rebuilt, but still runs great. It currently has about 240k miles on it. I realize excessive blow-by could cause oily air to flow backwards under certain conditions, so I'm not too worried about it. It's also been like that as long as I've owned the truck, so I don't think the high mileage is solely at fault.
The PCV system checks fine, draws air when it's supposed to. I think it's just the volume of oily air is just too much for the PCV system under certain conditions. Mostly I'm just curious to hear what others have experienced.
I've got a quick question about the Positive Crankcase Ventilation (PCV) system on our trucks. My '84 F250 (351W, 2bbl) has the original system with a hose between the air cleaner housing and the breather cap on the driver's side valve cover. As long as I've owned the truck (since 1992), I've always found a small amount of oil inside the air cleaner housing. I'm curious what others have experienced.
As I understand it, fresh air is drawn in one direction through this hose, from the air cleaner into the engine and then through the PCV system. The clean air supply is not drawn from inside the air filter itself, but through a separate mesh filter at the edge of the housing.
In theory, air is supposed to go in one direction only, but in my experience sometimes oily air gets blown back. I'm not talking huge amounts, more like a film or just a few drops at most. The engine is old and tired, never having been rebuilt, but still runs great. It currently has about 240k miles on it. I realize excessive blow-by could cause oily air to flow backwards under certain conditions, so I'm not too worried about it. It's also been like that as long as I've owned the truck, so I don't think the high mileage is solely at fault.
The PCV system checks fine, draws air when it's supposed to. I think it's just the volume of oily air is just too much for the PCV system under certain conditions. Mostly I'm just curious to hear what others have experienced.
#2
09-04-2016, 02:05 PM
If not getting a lot of oil in the filter housing I would say it is normal for a motor with 240K on it.
Also know a wrong PCV valve can be a cause. The "valve" that moves inside is made to work with in a range of vacuum. If it is not opening or closing when it should could cause oil in the filter too.
Dave ----
Also know a wrong PCV valve can be a cause. The "valve" that moves inside is made to work with in a range of vacuum. If it is not opening or closing when it should could cause oil in the filter too.
Dave ----
#3
09-05-2016, 12:44 AM
Post Fiend
Greetings All,
I've got a quick question about the Positive Crankcase Ventilation (PCV) system on our trucks. My '84 F250 (351W, 2bbl) has the original system with a hose between the air cleaner housing and the breather cap on the driver's side valve cover. As long as I've owned the truck (since 1992), I've always found a small amount of oil inside the air cleaner housing. I'm curious what others have experienced.
As I understand it, fresh air is drawn in one direction through this hose, from the air cleaner into the engine and then through the PCV system. The clean air supply is not drawn from inside the air filter itself, but through a separate mesh filter at the edge of the housing.
In theory, air is supposed to go in one direction only, but in my experience sometimes oily air gets blown back. I'm not talking huge amounts, more like a film or just a few drops at most. The engine is old and tired, never having been rebuilt, but still runs great. It currently has about 240k miles on it. I realize excessive blow-by could cause oily air to flow backwards under certain conditions, so I'm not too worried about it. It's also been like that as long as I've owned the truck, so I don't think the high mileage is solely at fault.
The PCV system checks fine, draws air when it's supposed to. I think it's just the volume of oily air is just too much for the PCV system under certain conditions. Mostly I'm just curious to hear what others have experienced.
I've got a quick question about the Positive Crankcase Ventilation (PCV) system on our trucks. My '84 F250 (351W, 2bbl) has the original system with a hose between the air cleaner housing and the breather cap on the driver's side valve cover. As long as I've owned the truck (since 1992), I've always found a small amount of oil inside the air cleaner housing. I'm curious what others have experienced.
As I understand it, fresh air is drawn in one direction through this hose, from the air cleaner into the engine and then through the PCV system. The clean air supply is not drawn from inside the air filter itself, but through a separate mesh filter at the edge of the housing.
In theory, air is supposed to go in one direction only, but in my experience sometimes oily air gets blown back. I'm not talking huge amounts, more like a film or just a few drops at most. The engine is old and tired, never having been rebuilt, but still runs great. It currently has about 240k miles on it. I realize excessive blow-by could cause oily air to flow backwards under certain conditions, so I'm not too worried about it. It's also been like that as long as I've owned the truck, so I don't think the high mileage is solely at fault.
The PCV system checks fine, draws air when it's supposed to. I think it's just the volume of oily air is just too much for the PCV system under certain conditions. Mostly I'm just curious to hear what others have experienced.
If you are getting oil in the air cleaner your engine has so much blow by the PCV can't keep up under certain conditions and is pushing the blow by gasses up the inlet in to the air cleaner. Very common issue on higher mileage engines.
Back in the day it was the quickest way to check the health of an engine, just pop the air cleaner lid and see how much oil was in it or the PCV in let filter.
The quick and dirty fix is to just install a higher flow PCV valve it will mask the issue for a while until the blow by get so bad it overcomes the higher flow PCV valve
#4
09-05-2016, 07:36 AM
If you are getting oil in the air cleaner your engine has so much blow by the PCV can't keep up under certain conditions and is pushing the blow by gasses up the inlet in to the air cleaner. Very common issue on higher mileage engines.
Back in the day it was the quickest way to check the health of an engine, just pop the air cleaner lid and see how much oil was in it or the PCV in let filter.
The quick and dirty fix is to just install a higher flow PCV valve it will mask the issue for a while until the blow by get so bad it overcomes the higher flow PCV valve
Back in the day it was the quickest way to check the health of an engine, just pop the air cleaner lid and see how much oil was in it or the PCV in let filter.
The quick and dirty fix is to just install a higher flow PCV valve it will mask the issue for a while until the blow by get so bad it overcomes the higher flow PCV valve
The following users liked this post:
#5
09-05-2016, 05:26 PM
Post Fiend
All PCV valve's restrict flow at times of high manifold vacuum IE idle and de-acceleration and the extra oil and smoke is already going in to the engine any way via the air cleaner and carb....... with a higher flow PCV valve it will not be fouling the filter element and carb.
I have upgraded to a higher flow PCV valves more times than I can count and it has never affected idle quality or drivability. The default high flow ford valve to go to is late 460 applications.
I have swapped in this valve in to everything from 1.9L 4 bangers to 400 8 Cyl and everything in between and it has never caused a drivability or idle issue.
Thread
Thread Starter
Forum
Replies
Last Post
DeathMobile
1973 - 1979 F-100 & Larger F-Series Trucks
10
05-01-2003 12:53 PM
Tom McGoldrick
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
14
04-10-2002 09:37 AM