Okay, this is driving me nuts. Maybe its normal to hear what sounds like a vacuum leak. I think I noticed this since I got the truck, but it runs well and economy is not bad. Recently I have been running without the beauty cover, so its a lot more noticeable. Today I removed the fan just to help isolating the noise, but I can not pin-point it. It sounds like the PCV valve. Its a new one, so I put the old one back in. No change. I went over numerous lines and the only way to make the noise stop was to remove the PCV valve at the valve cover. With valve still attached to vacuum hose the engine runs and the sound is 100% gone. So its not an intake manifold leak or any other hose. Or the valve or the hose to the PCV valve. So that leaves the valve cover gasket OR the valve normally makes a hissing/leak noise on its own when working. Also I put in two new VVT sensor seals.

My searching does not seem to bring up any threads on valve cover leaks. Thus I am not sure how difficult the procedure is. I am also not sure how to further test this idea. Any input would be appreciated.

 

I thought the same thing on my 2007 LR3 and came to the conclusion that is the PCV valve and completely normal. I noticed if you press down on the top of the valve it changes the tone of the hissing. I put a new PCV in and it’s still there.

 

I think you may be right. The sound is certainly coming form that area. I went back out tonight after the rain stopped and think it is indeed just the design of the PCV valve. When its removed and plugged its amazing how quiet the engine is though.

 

Both of mine make a noise at the valve to. I decided to believe it was normal.

 

Same here. It had me worrying that I had a vac leak but no other symptoms besides the hissing noise. I ended up replacing the PCV valve and the noise was unchanged. I've thought about putting something on/around the pvc to muffle the noise.