Ever since I bought my '95 22re 4runner it has used some oil. After I replaced the head gasket (5K miles ago), the amount increased to about a gallon a week to 10 days. I thought for sure the engine was shot, but no fouled spark plugs, no blue smoke (except for twice). I did a compression test, all numbers were within spec, around 170 across the board. So one day I thought I would just take the hose off the PCV valve and see if for some reason, some how, the PCV valve was sucking oil. Well I was right. The entire valve and hose was covered in oil. And the intake plenum was just wet black with fresh oil. So obviously it was sucking it in. I replaced the PCV valve with a new TOYOTA one last thursday, filled it up with fresh oil and now, a week later, the amount hasnt changed enough to be concerned.

I did the "suck" test on the old PCV valve to see if it was sticking, it seemed to move freely. I know basically all it is is a metal rod inside a diameter that plugs up when at rest, but lets certain amounts of air by depending on vacuum pressure.

How can the old one let by so much oil but the new one let by basically none? How do PCV valves go bad?

 

Ya know, I used to know the answer to this question years ago. As I recall, it had everything to do with the design specifics of the engine and rated spring tension. Aftermarket valves just aren't the same. The memory recall is vague, though. So, take that with a grain of salt.

 

Thanks anyway, Thook. The old one was a TOYOTA OEM. I'm thinking why after I changed my HG that it started using more oil was because I put on a different valve cover, with that PCV valve in it. It was from an engine I was going to rebuild and build up to swap in. According to the guy I had bought the engine from, it had 110K miles, mine was at 136K when I did the HG. But I would still like to know how/why PCV valves go bad.