New PCV Valve Rattling


#1

So I swapped out the PCV valve while changing the oil in my '02 civic and upon driving I noticed a faint rattling/buzzing sound. I only notice it at idle, whether because it goes away when I accelerate or because engine noise drowns it out. I grabbed my stethoscope and to my dismay found it to be the PCV. It’s not loud, but loud enough that I noticed it was out of the ordinary.

Now, I’ve read conflicting things all over the internet. Some people saying its perfectly normal operation, while others saying its a sign of a defective product. The old PCV was pretty gnarly, but did just barely passed the shake test.

Granted I did buy a Duralast (please spare me OEM nazis…:stuck_out_tongue_winking_eye: ), so I wouldn’t buy terribly surprised that it was a lemon, but maybe this is normal?


#2

Every properly functioning PCV valve that I have ever handled did make a shaking noise…when I shook it.
So, I am tempted to say that the PCV is okay. However, unless you can post a sound file, I can’t be sure.


#3

Are you 100% certain the PCV is the cause of the noise and that it’s not an excessive valve lash issue which can be from the same area?


#4

100%. Noise only began after installing new one and confirmed by stethoscope. Again it isn’t obnoxiously loud, its present, but not overwhelming


#5

Assuming the new PCV doesn’t have a flaw it’s possible this could be caused by vibration of the hose attached to it; especially if the hose is aged and hardened.
Maybe replacement of any hose or using a zip tie to lash it to something next to it would dampen any vibration which could then eliminate the noise.


#6

Are you the Civic’s original owner?
Is the PCV valve mounted vertically?
Are you sure it isn’t upside down?

PCV valves do have loose center pieces. In their static state they allow free passage of gasses from the area under the valvecover to allow the crankcase gases, which propagate up to the area under the valvecover via the return passages to the crankcase, and only minimal passage of gasses from the engine’s intake to the space under the valvecover to prevent any backfire from igniting the gasses under there, which may be saturated with hydrocarbon byproducts. The weight of the PCV valve’s center piece is low enough to allow pressure differential between the intake and the area under the valvecover to raise it and allow the free passage of the gasses, yet heavy enough that without a pressure differential the center stays down (closed), protecting the crankcase gasses from undesired ignition from a backfire.

Conditions that can cause a PCV valve to rattle are improper installation (upside down or not vertical), or erratic pressure differential fluctuations between the intake and the crankcase. The former can be checked by simply looking at the arrow on the PCV valve… it should opint toward the engine’s intake. The latter possibility can be easily investigated with a simple pressure/vacuum gage. If it exists, and the rattle bothers you, things that affect this such as valve backlash, compression, and such can be investigated further.

Post back. I’d like to work through this one with you, with help of course from the real experts here.


#7

This particular pcv valve screws into the block and has the nipple on the other end. Practically impossible to install correctly.

Its not nearly as loud as a valve issue. Its faint, I just don’t know if PCV valves normally chatter during normal operation


#8

They can if that difference in pressures is just at the right point, sort of analogous to a resonant frequency, but it isn’t usually obvious with the hood closed. A PCV valve’s centerpiece is, after all, loosely sitting in its housing in order to allow it to open with only a modest pressure difference. The design of the actual PCV valve can be a factor. If you tore valves from different manufacturers apart, I’m sure you’d find variations in how they did the internals. Your internal piece might be a looser fit, or pass gas slightly differently than the OEM.

Note that the rattle is harmless. You could even put some underhood insulation around the outside with a zip tie to muffle the sound if you wanted. It wouldn’t harm a thing.


#9

Following up on the same mountainbike’s idea of resonance: try pinching the hose a little (maybe with a zip tie or mini c-clamp) and listen for a change.


#10

If it doesn’t go away, you can always buy another one. I don’t know if there are OEM PCV valves but if there are, it shouldn’t make any difference which one you use.