Les had a belt noise which was resolved... my noise is in the video posted above.

 

My 06 super v8 is doing the same thing as mhamilton. It only tends to happen in the morning when it is cold < 35 degrees. It lasts for 10-20 seconds and then stops. Any advice would be appreciated. Thanks

 

Hi again mhamilton.

I just listened to your video clip and have to say that that is exactly the same as mine was. Only happened in cold weather though.
After changing the belt the problem was resolved. My very well known Independant Jag guy knew straight away what the problem was.
If I were you, I would change the belt, they don't last forever anyway. For the price of a belt and a few minutes work it could save you a lot of money.
Hope you sort it.

Regards. Les.

 

I did just recently replace the belt (was squeaking on startup). This noise may not be as clear in the video as in person. It's a definite "click" like a relay or electronic valve. And it's most definitely coming from the RF fender/bumper area, not the engine or belt drive.

I'm betting it's a control valve associated with the secondary air injector, and I don't think it's on the verge of breaking, but it does concern me a little bit. Knowing what I do about Jaguar so far, the entire pump will have to be replaced as a unit because of a $3 bypass valve.

 

That sounds EXACTLY like the noise mine made when it sat outside in cold winter nights. I am still leaning towards the air compressor, sorry. One way to be sure...disconnect fuse for air suspension system and start the car...if noise remains, les's suggestion bears more consideration.

 

No need to apologize, though I respectfully disagree. But I know it's nearly impossible to diagnose mystery noises from afar. If you were listening to it in person you could easily pinpoint it to the right front bumper--not the LF where the suspension compressor is, and not from the belt drive. I've listened with the hood open, both sides of the car, etc. It's such a sharp noise it's very easy to identify where it's coming from. The probelm is that it makes it for such a short duration that I can't get good diagnostics. I'd have to take the car apart, leave it parked outside overnight when it's cold enough, and hope it makes the noise long enough for me to listen with a stethoscope.

But anyway, it didn't make it yesterday or this morning. And with the weather warming up, it may not make it again until next winter. If that's the case then I'm not going to worry about it. May not even keep the car that long.

Pulling the fuse or relay is a very good idea. If I was sure the noise would definitely be there I could possibly yank the fuse for the secondary air injector. But then again, if it's a control valve, it could be on a PCM circuit not with the pump motor itself. Probably not worth worrying about anymore.

 

Have the same problem in my XKR 2000. A loud click every second when Cold. After a while (a minute) it's gone. The belt tensioner is jumping along whith the click-sound. My mechanic is sugessting to replace the tensioner and the belt. Will only replacing the belt do the trick?

 

ditto to this older thread - what was the consensus?
I actually just this past summer replaced both my belt and tensioner (and idler) as part of my big 100k service 'while I was in there'. I believe I used the top line dayco kit.
I'm getting the knocking now that it's cold.


I've also rebuilt my air compressor, hope people weren't finding the compressor as the issue.

 

I never did find the issue, but I know it isn't my suspension compressor. The compressor only runs once you're going 25+ mph unless the car is slammed to the ground and there isn't enough air the reservoir. In my case at least, the car was never low so the compressor had no reason to run on cold starts. If it still does it this year I'm going to start isolating components in the secondary air injector system. It either has to be the diverter valve acting up, or the pump itself.

 

Thanks Mr. Hamilton. I'll do some more checking, it does seem to come from the area of the driver side wheel well/front of the car to me.


I wonder if the belt tensioner is sticking or something in the cold, as it does go away after about 5-10 clicks or so.
I'd like to try to observe it when I start it cold. Lots of frost on the ground this AM here in Ohio!

 

Thanx for your reply, I listened to the video on the link and it is not the sound that is coming from my engine. I guess I used the wrong term in calling it a KNOCK sound, I guess it's more like it clicking tapping sound like a noisy lifter.
Thanx again!

 

Just for information, I had the same noise as Les had, and replacing the belt cured the problem fortunately.

 

Resurrecting this thread again - I just changed the belt on my 06 with 45k as preventative maintenance. Old belt was original so figured it was time, replaced with an AC Delco belt and am getting this exact noise at cold start for about 5 seconds. It's so quick and the belt/tensioner is obviously tough to see with such limited time so its been difficult to diagnose. I almost wish it lasted longer...

It is possible the new belt is bad? It the proper belt (6-rib 91") and the car runs and drives fine, have put about 400 miles on it since the swap with no other issues. Possible the tensioner is bad all of the sudden? I guess I could just put another belt on it, what brands are recommended? Have never had an issue with Delco parts but if that's the issue I'll definitely swap it. The noise sounds horrible even if its just for a few seconds at startup.

 

With the colder temps I am dealing with this with new belts. I put a phone camera on video record under the car and on startup the accessory tensioner pulls tight, then releases providing the intermittent 'thwack' sound. When this happened previously applying tension on the tensioner and trying to "even out" the distribution of the belt helped. I will try that again. All the belts and tensioners are new. I'll see if I can find the video and post, the sound is a perfect match for the other clips on this thread.

 

Thank you for the reply. So looks like this may be fairly common with these cars. I'd hate to replace a brand new belt that seems to be working fine, but the noise is just awful. Would also hate to replace a functioning tensioner assembly just to have the same issue. I will try as you recommend and maybe unload the tensioner a bit to see if it helps. Not sure what else to do. In older cars where it was hard to find replacement tensioners I used to let the belt rub over a candle and that would help with slightly loose or chirping tensioners, wonder if that would be an option here. I defintitely made sure the belt was nice and centered after it was installed so that's no issue and it should pretty much center itself after a few revolutions regardless. Would really like to resolve this, can't deal with that noise.

I'm not getting the whoosh/squeal noise in between the taps that I've seen in some of the videos. I believe that is due to a worn or slipping belt. Mine is just the very loud knocking sound that is also heard in the videos.

 

your tensioner is dying. i did this when i hammered the old one out to slap a new belt on

when it’s real cold it will seize and shred the belt

 

Interesting, thank you. Previous poster said they had the noise even with a new tensioner. Is it normal for them to go bad at lower mileage (under 50k)? Any reason not to buy a Dayco or Delco from RockAuto and go with an OEM? Seems simple enough to change so I'll probably take your advice and swap it out just to be sure.

 

There is also an Idler pully to consider.

 

Yes, but the noise is definitely coming from the tensioner assebly. It's a popping noise, not a bearing noise. I may just replace the tensioner and idler when I go back in there to make sure everything is good. Hate to replace functioning parts unecessarily, but would rather just be done with it.

 

There can be many sources of noise from the front but this particular popping noise in my case was the impact of the accessory belt tensioner arm moving -- the 'pop' is the sound of the arm hitting the metal rest. The car only has about 4, 000 miles from when I did the head gaskets, and at that time every pulley and every idler was replaced new (including the difficult to find supercharger idler), so I don't think my tensioner is failing. I'm going to take off the accessory belt and put it back on, and then with it back on I will let it sit for a bit then put tension on the tensioner a few times to even out any small 'bunching' or minor slack of belt on one side of the tensioner. This seemed to help when the problem originally surfaced. If that doesn't fix it I will try new belts, I think I'm currently running something from Rock Auto or similar.

Now, what I don't understand and would like to is *why* the tensioner arm is moving. Is it a slack issue on one side, is the tension too light, does it mean the belt is slipping, etc.