# Bad PCV Valve?



## How Do I (Feb 11, 2008)

I recently got a new PCV valve for the Blazer and this one is pretty loud. Chattering or rapid clicking noise. My old one didn't make this noise. Is that normal for a new PCV valve or did I get a defective one? You can actually hear it under the hood while driving (even with the windows up and the air cranked up). I never had this noise before from any other vehicles I've owned. Are there any _symptoms of a defective PCV valve_ that would confirm it is bad?


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## Travis in Louisiana (May 14, 2002)

There is no way this little valve can be causing all this noise. It should rattle when shaken, indicating that it is not clogged up and is good. The new PCV valve is either letting you hear other sounds that the clogged one was not letting you hear. The noise I am gusess, it coming from a valve tapping good or predetonation like you here with a low octane gas. To test, remove the PCV valve completely and see it the sound gets louder or goes away. If this valve is making all this noise, it will be a first for me. Just thinking out loud.


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## HermitJohn (May 10, 2002)

Yea even when I shake a pcv valve to see if its good, I have to hold it up by my ear while shaking it to hear the rattle. Its not going to be making some loud noise installed or uninstalled.

Chevies have all had engines with hydraulic lifters from late 50s on up so not badly adjusted valves. that can give you a nice clickity clack sound. So maybe bad hydraulic lifter. Or you have worn connecting rod bearing. If its definitely from the engine itself then probably one of those two things. Suppose it could be some bracket or something loose and rattling around??? 

Have you tried putting old pcv valve back to see if sound went away. Its either a coincidence and say lifter failed just as you were replacing valve or more likely while installing new valve you bent or loosened something that is now vibrating against something else. Put the old valve back in and tell us if noise is still there. I cant imagine any clicking engine noise a working or non-working pcv valve would hide.


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## How Do I (Feb 11, 2008)

OK. Can _bad gas_ cause pre-detonation? DW ran the Blazer low on the same day I replaced the PCV valve and I had to put in a few gallons @ our local gas station to get to the truck stop to fill up. Neighbor complains about the gas from that place all the time. It has been years since I've gotten gas from there. I put in 10 gallons of Super yesterday and I'm not hearing the noise any more. :shrug:


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## OkieDavid (Jan 15, 2007)

Looks like you found your answer.... That pre-det clanging does get annoying don't it?


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## How Do I (Feb 11, 2008)

OkieDavid said:


> _*Looks like you found your answer*_.... That pre-det clanging does get annoying don't it?


It seems so...with some help, of course. 

You guys & gals here are like the virtual _Encyclopedia of Mechanical Science_. I can't thank you all enough.:cowboy:


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