Hello all,
as I have mentioned in the past, after owning my 99 xk8 for 7 months, my dad really liked it and wanted me to find him a jag, he's always driven pretty shabby cars.
I found him a local 08 xk with a little over 100k and a solid/recent service history and good amount of highway miles, thought it would be better than my xk8, easier to get into + newer features and reliability edge over x100, and cost near double what I got mine for (although mine was a good price for the history and miles)
unfortunately, with time the car just feels a little lower quality than the xk8, still love the car and I get that this is because of the aluminum body and more sports orientated, interior etc, it is a beautiful fun car, but the road noise is pretty loud comparatively even with the suspension being all good, this is also a coupe and the xk8 is a convertible.

it makes a loud squealing/whistling sound at around 1500 rpms sometimes, does not seem ac related (only happens when driving certain speeds, ac occasionally makes a different small whirring for a couple seconds but it is not annoying), or alternator related, tested alternator on both cars and they both checked out good (despite battery not charging light on xk8) but I feel a little remorse and want to make the car better for him.
I have heard this may have to do with the intake separation leading into the cabin, which can be plugged, I also wanted to see if there was potentially any hole in the ribbing or something, also got 2 codes a little while ago, pretty much identical to what I got on my xk8, which with removing the intake, cleaning throttle body intake tube and maf sensor a couple days ago, made the codes go away, (k&n was oiling up everything in the intake, replaced it with non oiled) thought I could try to tackle a few issues at once on the X150 after the x100 intake refresh went smoothly.

only problem is, I cannot seem to find any solid resources with pictures or video on how to remove the X150 air intake online, and with the air filter being in the left wheelwell, the downward curve looks a lot more confusing than the xk8 was, definitely not going to try unless i know what i'm doing.
Anyone have anywhere they could lead me for some resources on this? maybe also any recent stories on whistling fix? the new front brakes also squeal loudly sometimes but plan to use cleaner on them as they are new but developed some surface rust before we bought it.
also could there be any sound deadening related things I might not know about that could explain the significant different in road noise between the x150 coupe and x100 convertible? I assume it's just the aluminum body. One other big possibility is that my xk8 does have better than stock tires, the xk brand I forgot, can check soon, they seem to be in good condition, might not be oem, but I don't know if it could make that big of a difference.

Thank you

 

I am in a similar, but reverse situation, in that I have had my 1997 XK8 convertible for well over 20 years and a few months ago my Son bought a 2006 XK 4.2 coupe (X150). Both cars have done around 70k miles and I maintain both of them.
If I could start with the general comment that our X150 coupe is, in every way, the more modern and sophisticated car. Quieter, smoother, more comfortable, more responsive etc. Our XK8 has a better exhaust note but that is only because I deleted the rear four silencer boxes and the over-axle pipes a few years ago. As stock, the X150 has the better tone although this is all subjective, of course.
Both our cars are on good tyres but different tyres do cause more or less noise so that is a possible explanation. A tired wheel bearing or two is also a possibility but that would tend to be a more directional noise. Binding brakes or a prematurely worn differential are also possible causes of noise.
Our X150 did make a slight belt squeaking but changing the idler wheel to the one with raised edges (search for Jaguar Technical Bulletin JTB00045) has partly solved the problem by restricting the squeak to start-up only. I will change the belt in due course but simply changing the idler pulley showed us just how much more difficult the X150 is to work on compared to the X100 so we need to find time to finish the job.
Your loud squealing does sound like a belt / pulley issue but I assume that you have released the drive belt and spun the various pulleys by hand and tested them all for bearing side-play?
The air intake on our X150 had been badly fitted by a previous owner/garage and the lip on the ducting was folded inwards creating a potential intake problem. This was discovered when we removed all the intake ducting right across the front of the engine to access the belt but we did not remove the wheel arch liner to access the part of the intake assembly which is in the wheel arch so I can't help with that. However, removing all the ducting from the engine bay was easy once you remove the two bolts on the power steering pump reservoir and pull it up to one side on its flexible hoses so I would be surprised if the remaining lower section was any more difficult.
I hope this helps a little.
Richard

 

To add to Richards description yes unbolt the X2 bolts from the power steering reservoir in order to access the ring clamp to the lower tubing of the intake .

Remove inner wheel arch liner and you'll see two further bolts that attach the lower intake ducting to the skirt/ rail .

The lower portion will then head off into a maf sensor then air box which is tucked up inside the lower front bar .

It's extremely straight forward I had my intake out last year in order to block off all the plastic resonators (including the piping heading into the cabin) and increase the amount of air I could get into my airbox . Over 4500rpm the sound coming from the induction is a lot deeper now very nice

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Thank you that info helps alot, to be honest its mostly shooting blind for me without finding much info on it online because I am not a serious mechanic, I do what I can do if I can find enough info on it. didn't know that the power steering reservoir was flexible, wasn't sure how complexly it would need to be disassembled on first glance.

I do think I described the sound a little incorrectly, it is a bit more of a high pitched dog whistle sound, it has a sense of humor because sometimes it will just stop when I am trying to troubleshoot it but will come back at max when back driving. Especially immediately after I say "wow it hasn't done the sound in a little while" It has been intermittent and not affected driving, have an obd2 temp gauge etc to monitor the car to a certain degree just incase it could lead to something catastrophic, but it seems intermittent and air related. I have not hand tested the pulleys, but I will try to get to that as a next step if intake checking doesn't work. The sound if I could generally pinpoint it sounds like it comes from right ahead of the dash area, which is why I was wondering if it was the cabin intake splitoff and wanted to check.

I do not have a recording of the sound at the moment, but it seems influenced by the amount of throttle the car is getting at lower/normal rpms. I will try to get a recording of it soon.
The brakes still look a little rusty still from sitting a little before we got the car, most of it is gone from driving, but I really hope the brake squealing just needs a clean and is not differential related, dad got quoted 4000 recently to fix/replace a jeep differential my grandmother gifted him that exploded a few months ago. Has a new motor and bunch of work already so he's probably going to bite the bullet at some point. I assume jag differential would be near double that or something crazy, although the jag specialist it had been to before did say the car looked good before we bought it.

To be clear, I am not putting down the X150 at all, it is an amazing car, love it, the remorse I felt was more in the sense of the car being a bit more expensive than mine but having some annoying things related to I assume the car in particular and not the general design or engineering. If I was to compare them from personal experience, the X150 definitely has the better exhaust sound, it has bigger seats and larger interior, it is significantly more responsive although the xk8 does not feel underpowered either, sharper steering. the X100 just feels quieter overall at the moment, I would say the x100 looks more e-type-ish, x150 looks more aston with series 1 fhc elements, neither of which are bad things and both are beautiful cars, personally prefer the x100 interior but I am not strongly leaning towards one or the other, just wanted to figure out the road noise because most owners seemed to say it was not very different than the x100 and in this case it does feel a bit louder, hopefully it is the tires and new good quality ones when the time comes makes a difference.
Thank you.

 

Really helpful info thanks, so I assume it has more than one resonator, not just the cabin, a bit like the x100 xkr intakes?

 

Am I understanding correctly- you removed the Helmholtz resonators on the intake pipes between the TB and the airboxes? I've been rolling this around in my head for a few years but never pulled the trigger because it was an irreversible mod to the parts and I was afraid there'd be too much SC whine (I'm really not a fan). Did you make new pipes or just cut them off and seal the holes? If sealed, what did you use? You say the induction note is deeper, do you mean when you open up the intake on an NA engine? How much louder is the SC whine? Any videos of the sound?

 

Mandrake mines a n/a 4.4 (out of a petrol range rover sport) so no supercharger whine

I used the original piping cut off the herm resonators and sealed up the holes with black flat caps that are the correct diameters so they sit flush

Whilst there I also opened up my airbox and in terms of sound yes it's deeper how can I put it .. it sounds like it's a significant larger displacement engine now after 4500rpm

 

Problem resolved (I think), this info will still all help me when I do clean the intake and maf sensor, but I believe the source of the shrill whistling was actually the AC blower fan going out and now dying. the sound seemed to come from in front of the dash area, ordered a new blower motor resistor but not sure what I should do about the blower motor, because some people had said the OEM ones were not properly sealed for water? and they are prone to duckbill flood damage, weighing getting the OEM replacement or getting a different motor people in the forums talked about, and modifying it (screw shortening and soldering), price difference is $50 for diy and $150 for oem, price isn't a huge problem here but if the oem will last shorter due to the drain, then diy would seem more favorable.

 

I've done this with custom CAI and yes supercharger whine's more pronounced.