Air noise when coasting/slowing without braking

C

crispy

New member
Hi all,

I have noticed a noise that sounds like a rapid release of pressurised air or, possibly a breaking of a vacuum allowing sudden inrush of air when I take my foot off the accelerator and coast (say, up behind queueing traffic at a red light before starting to brake). It seems to come from just over my left shoulder (right-hand drive car) but I might be placing it wrong.

It's possible that it has always been present and I've just not noticed before. I've had the car 6 months from used (2018 V6 convertible with 40,000 miles and still has 6 months dealer warranty).

It's quite quiet and seems to do it three or four times, maybe just before the automatic gearbox changes down - not sure on that one yet. I'd say it lasts about a second each time.

Does anyone recognise this or know what it is and what I should do about it?

Thanks in advance

Chris
 
Do you have the heated/cooled seats?
Positively, when on, these have a fan which you would hear behind your head when you lean a bit forward, like when braking.
 
ralphr1780 said:
Do you have the heated/cooled seats?
Positively, when on, these have a fan which you would hear behind your head when you lean a bit forward, like when braking.
Click to expand...
No, neither heated nor cooled.
 
Update:

I've done a bit more testing - it seems to do the same thing whether I'm coasting or braking. As the car slows there's a puff of pressurised air every few seconds and it doesn't seem to matter whether it is in dynamic mode or not, or even in standard mode but with active exhaust engaged, or not. The one consistent speed it does it at (although it also does it a few times at other speeds as the car slows) is around 20 mph as long as the speed has got over about 28-30mph. ie I was in slow moving traffic, slowed down as I caught up with the tail, tail moved off again so I accelerated gently then let off the accelerator to coast and, as long as the acceleration took the car to over 28-30 then the air puff noise happened as it slowed, at around 20mph.

The noise itself is not a problem at all - can't hear it with music on, in sports gear selection, or with the top down - but I'm concerned that it indicates something that needs addressing.
 
Do you find the noise in the area of the shifter?
Try with the roof up and shift through N, D and R a few times.
 
Tel said:
Do you find the noise in the area of the shifter?
Try with the roof up and shift through N, D and R a few times.
Click to expand...
No, it's definitely coming from behind me.

It happens on the move so I can't shift through N, D and R unless I'm stopped. I can ONLY hear it with the roof up....to much background noise otherwise. When I do go from N to D or from N to R I don't hear it but that doesn't surprise me as that's not the situation when it's happening anyway.

Think I'm going to have to take it into the dealer in case it's something that needs attention under warranty.
 
OK.

You can shift from D to N and back whilst on the move, but as you say if it's not that area, and judging form the age of the car you don;t have the air pump and accumulator that was on very early cars for activating the exhaust flaps, it can't be that.

If there's no warnings coming up on the dash, I'd be inclined to delve a bit deeper before going to the dealer.

Could be something loose rolling forward under deceleration? You do have a parcel shelf that is exposed when the hood is up. Remove the air buffer shield between the headrests first to get into that area...
 
Mystery solved....the puff of air that I hear when coasting from about 35-25 mph has been identified & diagonsed by an independent Jaguar specialist. The active exhaust (I think he said on the off side) is seized and has caused the actuator rod to break. I'm told the noise I hear is the vacuum-driven actuator attempting to do it's job but failing because of the seized exhaust and, now broken, actuator rod. Booked in AGAIN for warranty repair with the dealer who said there was nothing wrong.
 
scm said:
NavigatorNI said:
crispy said:
.... with the dealer who said there was nothing wrong.
Click to expand...

Surprise, surprise! Sorry if I sound a tad cynical.
Click to expand...

That's what happens when there are no codes to look up ....
Click to expand...

Yep, and that theory is supported by the phone conversation I had when I booked it back in...the lady on the phone just didn't know where to go with the discussion when I told her there were no warning lights on the dash!

Computer doesn't know of an issue, therefore no issue!
 
Good luck with the dealer/warranty repair….

I was of the impression the exhaust valves weren’t covered by warranty. 🤔
 
The Jag specialist who diagnosed it told me everything it needed was covered but I'll check ... nothing would surprise me in relation to main dealers.
 
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