Hey guys,
I have developed a hiss lol. Check out the video. I do not know what the name of the part is that is making the sound, if you know please fill me in! Click on the picture below and it will bring you to photobucket to watch the video. Thank you!

 

Normally a hissing noise is associated with the inlet side of the engine, and happens when a vacuum hose, a gasket, or a seal starts leaking. This leakage of air around the normal inlet passage causes the engine to run badly as the air flow is now different to that detected by the MAF.

Looking at your video, and not being familiar with the V8 engine, I don't know what the function of the component you indicate is, but it could be related to the engine breather. In normal running, the breathing system is designed to provide a slight vacuum in the engine. So blow-by past the piston rings and the exhaust valve guides gets vented to the inlet passages somewhere. As this gas gets charged up with oil vapour in the engine, the breather normally has a filter somewhere to extract the oil before the gases are passed to the inlet manifold.

Is the car running totally normally ?

 

That is the EGR valve. Not to long ago a fellow member in the XK section had a problem with his, I will try to remember the thread and post back.

In the meantime, if you remove the black plastic engine cover (usually a couple of short screws) you may get a better look at the vacuum connections. If you happen to have a misting bottle you can mist water on the vacuum connections if the engine changes rpms (while running) you have a vacuum leak. Carb cleaner will work as well, just be careful.

Link: https://www.jaguarforums.com/forum/x...80/#post475691