Oil coming from the filler cap. Questions about Blow by

[Americanclassicg]

My 97 aspire had been leaking oil all over the valve cover from the PCV valve, and the filler cap as well for a while. It was never much, until I just changed the oil (I let it go a little long ) with 5w30. Now its puking quite a bit on the valve cover. Enough for it to get visibly wet all over the top of it in my 20 minute drive to work.

I figure, ok, PCV valve might be clogged. $3 for a new one, Id rather pay that than even check the old one. Still leaking from the filler cap, but not so much (seemingly, but I havent driven it beyond the 10 minute drive home form the parts store) from the PCV. It is a better fit on the grommet though, which probably helps.

I pull the vacuum line going to the PCV while running, and it is pulling vacuum, and the valve it pushing pressure out.

I pull the filler cap while its running, and it starts blowing smokey fumes out. The plume reaches about 6" high before it begins to dissapate, but the pressure from it only makes it about half of that before becoming ineffective. When the gas is pressed, a slight vacuum ensues, as it should. Obviously, I cant test this under load though.

My questions:
How much blow by, if any, is normal?
Should it be smokey?
Should my filler cap have a rubber gasket? It doesnt have one at all.

[blkfordsedan]

It would be normal to have a little blow-by, depending on the mileage, but the less the better. With the PCV hooked up and the engine at idle, it should be pulling a vacuum under the valve cover. The best way to tell how much ring seal you still have is to do a compression test. Once it has developed some blow-by, combustion gasses will start to contaminate the oil quicker, so frequent & regular oil changes become very important. It won't get any better, so run it as long as you can. Eventually it will start to push oil through the fresh air hose connecting the valve cover and the air intake duct. When this happens, it will cause oil to run down into the air filter and VAF sensor...as well as sucking oil into the throttle body and intake manifold. The oil in the combustion will cause predetonation and foul the plugs. Pull your air intake tube and check it for oil. Clean your TB and check your air filter on a regular basis. Basically, it becomes self-perpetuating and can start to go down hill fast if you ignore it. You can still get some good miles out of it if you keep on top of it.

[frogman]

^ X2
A compression check will tell you a lot. If they are all about the same it is most likely the rings. Just checking the looks of the plugs can tell you a bunch. If they are all fouled with burnt oil fouling you don't need to go much further. One bad cylinder and could be a cracked piston.

[nitrofarm]

Yes you have to have a rubber O Ring on the bottom of the Filler Cap. You cant expect the PVC to work properly without it. For some reason the O rings on my Aspires like to fall off also.They did something different on the design IMO because I've had this problem.

[WmWatt]

If you don't have a compression guage to do a compression test try removing the spark plugs and inspect the colour of the electrodes to see if they are oil fouled. A search of the Internet will bring up photos with explanations of the various colours of spark plug electrodes.

[bravekozak]

Buy a nice Mazdaspeed oil filler cap and reef it down on the o-ring.