Hi everyone, just joined the site as just bought my first jag after being an avid Subaru rally fan for years. Was time to move on and up to a XKR supercharged and certainly seems the right car! Smiles all round!

It's a 2008 but only done 19,000 miles

Right, down to my potential problem.

At a constant speed, say 50+ there is a noticeable sort of 'pulsing' from the engine bay, around 4 secs on and 4 secs off.
I wouldn't have said 'surging' as no difference in power.
The guy who sold me it said it was normal and just the supercharger. Having driven it for a couple of weeks, I don't think it's normal but I've got nothing to compare it to so hopefully someone on here can put me straight?
It's not a loud noise but you feel/sense it through the car if you know what I mean.

The performance is fine and you can't notice this until higher constant speeds but at all speeds when cruising. I tried to film the sound but it doesn't really pick it up. Can't really notice under heavy acceleration.

I've read about resonance and a bracket fix but I would have thought that would be a constant drone and not pulsing like this? I've had loud resonance on my old Subaru but it's weird that it 'pulses'.

Could it be the supercharger?

Mmmmmm not had anything like this before but this is my first supercharged car.

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2008 XKR (added by GGG)

 

Welcome to the forum Swisstone,

I've moved your question from General Tech Help to XK/XKR forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

I can tell you that it absolutely is not the resonance issue on early cars because my 07 had that. That came on at about 1200 rpm and stopped at about 1600 rpm and was a steady drone under the floor, not a pulsation. And yes, the bracket that Jaguar designed for the catalyst eliminated the drone effectively and permanently (if not cheaply).
Your noise is different and I have no answer for you but could it be related to the AC compressor cutting in and out?

 

I think Gregory is on to something. I would bet it has something to do with HVAC system and the compressor. Does it happen all the time or just when you have climate control system on auto setting?

 

^^^^^ +1 on Gregory and tberg. I'm nearly deaf and had the same problem on my initial drives. The temp was set to auto. I shut off the A/C, problem gone.

 

The droning issue only affected the XK anyway, not the XKR.

 

Thanks for initial help guys! Sure it's all the time and aircon doesn't make any difference but I'll verify that tomorrow. Been out in it today a and you can start to hear/feel it from 35 mph and gets progressively worse as speed increases but more noticeable at constant speeds. I would say more 2 secs on and 2 off now not 4 if that makes a difference! Cheers

 

Could it be tires? They can wear in a way that mimics mechanical noises. Also check your your front wheel bearings for any sign of free-play or a wearing grind noise. Both are road speed sensitive and have the capacity to set up a resonant rumble.

 

I know what you mean about tires as I have had castellated tires before but sure it isn't that. Last time I had that it was a whine that got louder and like you say, similar to a bearing going. I tried to video it but wouldn't really highlight enough. It does sound mechanical and can also describe as a resonating spring that's pulsing. Weird eh, never heard anything like it.
The engine sounds perfect at idle or Erving on drive.
It's also only covered 19k miles if that makes any difference.

 

I've had a case where I could swear the transfer case on an AWD BMW was going bad and making a gear wear noise. I was ready to buy a replacement case when I punctured a tire that could not be repaired and bought a new set of rubber. To my amazement it was the tires. I've been driving a wrenching for 50 years and thought I knew my stuff. I learned my lesson.

Yes, I would agree that at 19K most wear items would not be going bad. But you have some kind of issue going on. Have you considered an underbody panel that my be resonating at speed?

 

Yeah noises can play funny tricks with you eh. I have been under car and everything secure. It does seem from higher up though and a very unique sound. I think like the other guys said, need to investigate air con and if not, have the supercharger looked at. Will turn off the air con tomorrow and see if makes a difference. Don't tend to leave it on auto. Hopefully when I get to the bottom of it, I'll let you all know.

 

Please confirm tomorrow that it's not the A/C and in the meantime, turn up the radio. I Find that fixes almost all noise problems.

 

Even though it would engine speed related, I'm wondering about the serpentine belt. If a funny wear pattern could set up a noise like this. Examine the inside teeth of the belt for unusual wear pattern.

 

A couple of weeks ago, I had a noise that sounded like a bag of rocks being tossed in a dryer. I was certain that it was coming from the supercharger, and that possibly SC bearings were in need of replacing. It turned out to be the water pump wobbling so badly that it was making the noise. Replaced the pump and the cacphony subsided. Just a thought.

 

Morning all, well turned the a/c off/on and no difference to the issue. What exactly is the serpentine belt? Haven't completely ruled out front tires but it's the pulsing that doesn't fit with that and usually an increasing whine. It's going into the local specialist on 14th march so will get them to test drive and report back. Wish I could sound record it for you all to hear!

 

I had a similar issue that was driving me batty. Then I noticed the rt front tire was wearing like crazy on the outside edge. Got an alignment and problem solved.
The mystery is that the car was steering and handling perfectly during the whole process. And yes, the droning was rhythmic and it would come and go dependent on road surface/speed. Go figure.

Too bad I wasted a good tire before I got wise. I need to mention this was on my 2012 Chrysler 300C.

 

Cheers but funny enough I've just had the tracking all set up this weekend on a 4 wheel alignment machine as it did drift off a little. Not made any difference to the problem though!

 

Did you have all 4 wheels spin balanced immediately before the alignment was done? If not, get them high speed balanced. You can't see a defective tire belt since they're internal, but it should show up on a high speed balance.

 

No didn't get the front wheels spin balanced as have no steering wheel wobble so just got alignment/geometry set up (not cheap) but it's an expensive laser 4 wheel machine to recoup cost of! Ha. I wasn't doing this as part of the current problem, just needed doing. Castellation of tires is uneven tread wear isn't it so you think that would show up on a spin balance? If the local garage has a spare pair of wheels, another option to swap over if willing?

 

If I were you, I would want to rule out defective tires. It's not expensive and worth the cost. Just because it doesn't shimmy doesn't mean you don't have a damaged tire.

It doesn't take much of an impact from a pothole or curb to cause a belt in a low-profile radial tire to separate or be damaged, even if there are no obvious signs such as a bubble in the sidewall or uneven tread wear. To determine if a tire has a separated belt, put it on a wheel balance machine and make sure that it runs true by watching the sidewalls and tread for any in-and-out, up-and-down, or side-to-side motions. Also make sure that the wheel rim runs true.

Your stated that you recently bought your 2008 XKR with 19,000 miles. Does it still have the original tires? If not, when were they replaced, and how many miles ago? What brand and model? What are the F/R cold inflation pressures? How many previous owners and do you have all the service records? Any history or other evidence of front end damage?

Stuart