Greetings! I am trying to help out my brother, whom has a 2003 STR. It is making a knocking sound from the top end. Definitely doesn't sound like valves or rod knock.
Mechanic says its a supercharger waste gate or bypass valve? Could someone with more knowledge than I point me in the right direction with perhaps a part # or diagram?

 

Doubt it. the wastegate is the black 2" diameter hose at the back of the blower connected to the intake elbow. theres nothing that could knock like that there.

 

Remove the SC belt and start the engine.
Listen for the noise again. (no noise=NOT the SuperCharger)

 

Meaning if you hear the noise = NOT the supercharger.

If all is quiet =SC related..

 

i agree , but this really depends on the failed part .
as the engine will actually spin the blower with vacuum even without belts on ,
and if it has a failed bearing causing rotor contact you will still hear it with out belts on .
though if you remove the belts and spin the blower by hand it surly will rule this in or out .
my money is on a broken supercharger snout coupler , very cheep and common fault with the roots blowers .
mine has done this and does sound knock'y .

heads up though with the upgrade coupler .

https://www.jaguarforums.com/forum/s...ads-up-176686/

 

I may have some useful information to add. A few months ago I also experienced what I would call a knocking type sound coming from the top end of the engine like a faint rod knock but from the supercharger area. At first I thought it was the supercharger itself because it had been low on oil right before the sound manifested - my mechanic told me the engine was probably not running on all 8 legs judging by the sound of it.

After taking some stuff apart, I found out my actual bypass valve on the elbow near the throttlebody was destroyed because the plastic cracked where it is fixed onto it's bracket. (It basically pushed itself off of the bracket under boost) Also, the bracket itself wasn't bolted into the throttlebody properly, a bit of loctite fixed that. The actual part for a the Jaguar branded bypass valve is AJ82715. These bypass valves are pretty generic across all brand of cars and worth about 20 bucks I reckon but the way these are fixed with rivets to the bracket means you need to buy an expensive Jag one. I bought an intake elbow with the valve on it for way less from the wreckers (AJ812474).

This is easy to diagnose. The bypass valve should be plainly visible, if you can move it by hand - tighten the bracket and if it comes off of the bracket... well then its broken.

I also have to agree with the gents though, there is a big chance that the coupler in the supercharger's snout is broken as it will cause similar noises and is also easily diagnosed and fixable.