I'm hoping someone might have an idea as where to start in this diagnostic process. I noticed that shortly after start-up my 2013 XF 3.0 AWD develops a knocking in the engine compartment. With the hood open the knock is very noticeable. It starts as soon as the engine settles down and maintains a steady idle state of about 800 rpms. You do not hear the knocking until this idle state starts. When it initially starts and the rpms are above 1,000 it is not noticeable. In between 800 and 1100 it is very difficult to determine if the knock is rpm dependent. I took my stethoscope and tried to identify a location, but the best I can isolate it is near the idler pulley shaft as it extends back into the center of the engine. The knock is not definitely noticeable in other locations around and on top of the engine. The knock disappears as rpms are increased, but not sure as to whether this is due to the knock disappearing or the resulting natural increase in decibels from the engine masking the knock. When you rev the engine the knock is not noticeable above 1,200 rpms. Engine oil is at specification. No performance decrease and no error codes to examine. I have attached a recording of the engine at idle. The normal engine noises are apparent but in the background you can hear the deeper knock, knock, knock. This knock is lower and deeper in tone than the normal higher pitched engine noises. I hope that makes sense. Any ideas would be very welcome.

 

I just visited with my local mechanic and decided to stump the experts. This shop is fantastic because they love the unusual and a challenge. Darin and Justin listened and thought for a while, made some notes and started thinking about the turbocharger. I went home fully satisfied that they did not come up with a quick and simple answer. Ah Ha, stumped them! About 10 minutes later Justin calls and tells me about some information he has been reading on the Eaton supercharger isolator. Now they are not positive about this, but thought it might be worth a look. They assured me they would be doing some more research. Nice eh? I'm pouring over the Service Manual now in an attempt to find the answer before they do. Ha Ha. The next step is to remove the power belt, reconnect the air intake and see if the noise disappears. Also, maybe give the turbo pulley a whirl and see if it is lumpy or sticky. Fun.

 

Why are you talking about a turbo?
It has an Eaton TVS R1320 supercharger with not a turbocharger in sight.
And yes the noise could be the torsion isolator / coupler rattling, this is very common on both the AJ133 SC V8 and AJ126 V6.
I had this rattle on my F-Type and had it fixed under warranty, the official JLR warranty fix involves replacing the entire snout of the supercharger (with the isolator inside) and not just the isolator. However many have replaced just the coupler with either a later generation OEM one with the spring in it or an after-market 100% plastic one with no spring.
There are masses of threads and posts on this forum in the XK, XJ, XF and F-Type sub-forums about this coupler.
That said, the coupler rattle is a rattle, like a can of marbles, and not a deeper knock. It's also a very irregular rattle which comes and goes and not a rhythmic knock.
One of the common symptoms of a worn coupler is a loud "clonk" when you turn the engine off, not every time but about 1/3 of the time.
Yes, it's a good idea to slip the SC drive belt off and check for the noise, if it's not there you have narrowed it down to the SC (and probably the coupler) but if it is still there then you know it is something else.

 

My sincere apologizes for referring to to the supercharger as a turbo charger. I hope I did not offend anyone, but it has been a long time since my F-1 days when we referred to anything that boosted air pressure within a confined space as a t-charge.
I'll be sure not to offend anyone else by leaving the forum.
Bye.

 

Oh BTW, I still have my McLaren!

 

What just happened!?

 

I have no idea. But that knock does NOT sound happy, pretty sure that's in the bottom end.

If I had to take a guess, that's rod knock and a bearing has let go. Just a guess as it's hard to identify, but almost certainly not the supercharger isolator spring.

 

I would get a stethoscope and probe around to verify where the noise is coming from. With all the moving parts on the car it is often hard to pinpoint exactly where the noise is coming from. Just be sure that you do not interfere with the moving parts.

Link https://www.northerntool.com/shop/to...xoCt78QAvD_BwE

 

Sounds like a timing chain whipping around from lack of tension.

 

And you're still mentally unstable.

 

Did you ever figure out what the sound was Steven? I have something similar and haven't taken it in yet. It's hard to find with a stethescope since it seems to resonate everywhere, but I hear it on the end of the passenger side valve cover more than the driver's side valve cover. Can hear it on the bottom front of the oil pan as well, but maybe not quite as loud (hard to really tell). I'm curious what you found out.

For others - let me know if I should start a new thread or continue discussing here.
Questions:
1) Sounds like people don't think this is a supercharger sound - is that right? I can hear it on the top of the supercharger lightly - more on the passenger side of the cover than the driver's side.
2) Are spark plug connectors very accessible? I would try to pull one by one to see if the sound goes away if I can get to them, but it looks like that may be fun
3) Much fail around the valve covers on these? So far the place I can find it the most is on the front of the valve cover, although there's a lot I can't get access to easily.

2014 XF 3.0 AWD ~75k miles.

Thanks!
Austin

 

Looks like Steven threw a hissy fit and spat the dummy three months ago when I politely informed him that his car has a supercharger and not a turbocharger, so you/we won't be hearing from him again!

 

You say politely and I say "man I would hate to see what is was like to have you be an @ss to me.". My feeling is your response will tell me that.

He obviously misspoke and you said "Why are you talking about a turbo?
It has an Eaton TVS R1320 supercharger with not a turbocharger in sight."

Mighty snide comment to me. I don;t really blame him though, I have been lurking here for a but trying to find out info on my new to me XF and have seen many comments that are less than welcoming to new members. And your response above calling his reaction a "hissy fit and spat the dummy three months ago" seems as if you were happy you chased him from the forum.

You are an @ss dude