Hissing from rear CCV grommet

[bromel]

Hi guys, for a while now I've noticed a very faint hissing sound coming from the rear CCV elbow/grommet of my 2000 4.0. Hard to notice, but confirmed with a stethoscope. My idle RPMs are around 550-600 when hot, no stumbling. Before I go ahead and replace the elbow and grommet, can anyone else confirm if it's normal to hear a slight hiss from that valve? It's a vacuum line connected to the intake, so I'm assuming the rubber has become old and brittle and is allowing air in from the outside.

Thanks!

 

[pagrey]

It's normal, it can flow air at idle. Nothing wrong with changing the grommets, just look at the elbow when you take it apart and be sure it isn't damaged. You might also check your oil cap and dipstick to be sure they are clean and are in good condition. More leaks could mean more flow at idle. I think the IAC will adjust to keep the idle steady even if you've got cracks here and there.

 

[bromel]

Yeah, I haven't noticed any performance issues, just that slight hiss. I'll probably ignore for now and just replace the grommets/elbows when I do the valve cover gasket later this summer, so I don't have to worry about any plastic shards falling into the engine. Thanks!