Stopping my XK 5.0 popping and banging on overrun

[Garry1127]

I know this may sound like sacrilege to some but I find the constant popping and banging from the exhaust on overrun irritating.

Is there a way to stop it?

[N6 JMX]

Hi Garry, if the 5.0 XK is continuously making the overrun pops and bangs, then the most likely culprit is the active exhaust valves may be stuck / seized in the open position. Alternatively, you have it permanently in "Dynamic" mode, the button on your centre console has been pressed. This latter option should give you a message in the dashboard.

Unlikely, but another option may be that the previous owner fitted an aftermarket exhaust that is predisposed towards the noise.

N6 JMX

[Garry1127]

Hi Jim,

It only pops on lift off or down changing, so not continually, it has the standard exhaust and I don't drive it in dynamic mode, another XK 5.0 I drove before selecting this one did the same.

Its just a bit chav like, the noise the engine makes on down changing is nice enough it doesn't need the pops which I find a bit jarring.

I was hoping that there was a setting to turn it off.

If I remapped the engine could I instruct the remapper to stop the popping?

 

 

 

 

[N6 JMX]

Hi Garry, "by continuously" I meant making the pops and bangs on lift off / overrun / down shifting, not whilst driving along on a continuous throttle setting. The car / exhaust should only do this if either Dynamic Mode / Sport Mode (gear selector moved all the way to "S") is switched on, or by the sounds of it more likely the valve mechanism in the exhaust has seized into the open position. The car will also make the more "throaty" noises at engine speeds in excess of 3,000 RPM when the exhaust valves will automatically open 0 if functioning correctly.

I am assuming that your car is a naturally aspirated (NA) XK and not the Supercharged (SC) XKR. In the NA cars, with a single tailpipe on each side, the exhaust silencer / rear section, has a "Semi Active Muffler" Valve or SAM. There is a SAM on either side of the rear section - back box - and the SAM are fitted with spring loaded, normally closed in general operation. The following is a quote from the service / workshop manual:

"The SAM valves vary the tone of the exhaust to give a more sporty sound at higher engine speeds. The SAM valves are normally closed, spring loaded check valves. The SAM valves are non serviceable and the muffler is replaced as a complete assembly."

If the SAM are damaged / stuck open, then you get the effects - all of the above assumes a NA car and a standard NA exhaust, i.e. not an aftermarket exhaust, which are generally tuned to give extra pops and bangs.

N6 JMX

[Sev90]

Before I brought my 5 Lt XK I looked at many and watch so many hours of U tube it all started to go blurry but the one thing most reviewers commented on was how a std system was so quiet with out pulling fuse 19 or swapping the rear pipe . But during my test drive it didn't  sound to muffled but the weird thing was I didn't notice the quad pipes at the rear till I'd looked at a few more, so on a return viewing a quick look under the rear revealed a lack of Oil drum size silencer which some might see as a bad thing I just saw a £800 saving on replacing it anyway.

As I enter my mid to late 50s my feeble attempt to grow up and be more age appropriate seems to be a dismal failure.

Pete.    

[Garry1127]

Hello N6 JMX,

I have the car in standard mode so not in Dynamic or sport.

Are you saying that a naturally aspirated 5.0 V8 like mine should not make any pops and bangs on downshifts unless in Dynamic mode?

Garry

[N6 JMX]

Hi Garry, if your car's settings are in normal driving mode, then the 5.0 litre NA XK should not be making pops and bangs at any point in normal driving. Are you certain that your car has the standard NA exhaust system fitted? The image below should be what is under your car. Note that there are aftermarket tuners who will create exhaust system for your car that eliminates the centre silencer and this will allow the engine / exhaust note to be "fruitier".

Note, if you click on the image it should open as a separate window and allow you to magnify the image to see close-up views.

N6 JMX

 

[Garry1127]

Hello M6JMX,

I have looked under the XK and the exhaust looks standard.

[N6 JMX]

Hi Garry, yes I can see the rear silencer, but there are also 2 x silencers at the mid section, which is not shown in your photo. One of the "tuning" options that folks choose is to replace the centre section of the exhaust with straight through pipes, i.e. removing the central silencers. This does have the effect of making the car sound rortier. Need to check that central silencer box is there.

Failing that, then the last remaining option is that your SAM valves are stuck open, resulting in the pops and bangs on the overrun. These are just visible in your photo, ahead of the tail pipe, there is one on each side of the muffler. They are not serviceable, but a local mechanic might be able to check and try freeing them off.

Don't have any other suggestions for now.

N6 JMX