knock knock knocking on.....the front of the 997

[dan.hockey1]

Right, I'm at the end of my tether (as is my specialist lol) with a slight rattle/knock, and I thought maybe someone here knows what it may be?

It's not bad on normal roads but we have a local road which is quite 'bobbley' on which it sounds worst. It's been there for a while and i've tried lots of things to no avail.

It seems to be drivers side to middle from in the cabin, I've attached a quick video, it sounds much worse on the video but that my help identify it!

I've had full coilovers fitted (which have also been back to the manufacturer to check and they are sound), then the coffin arms, and tuning forks fitted, and anti roll bar bushes, new brake discs, pads and fittings, they've also checked the drop links and track rods, i've had the arch liners off, had the frunk liners out, checked the undertray mounting points, coolant pipes, battery, bonnet, bonnet struts and latch, wipers and mountings ........and we still can't identify it ...........maybe a mouse with a spanner hiding in the dash, tapping on the back of the rev counter??

Any thoughts....please ?

 

[Rodney Naghar]

That’s quite bad.
Have you tried front strut top mounts, steering rack mounts or the roll bar drop links (they haven’t been replaced)

 

[marc_tt]

Sounds like you've changed or checked the obvious suspension and steering parts. Have they also checked engine and transmission mounts.

Suggest find a local MOT tester which has a pit with 'shaker pads', where you park the front wheels on the pads and then they shake the car and you listen and look from the underside for the source.

Had similar with failing engine mount and recently with a people carrier where ended up finding a spanner in the suspension that had been left from a previous repair.

 

[Scrounger]

I’d also take everything out of the car. Empty the glovebox and the centre armrest and door pockets. I had an annoying little rattle a while ago and could fathom out where it came from. Turned out to be my Porsche key ring chinking against my front door key.

A friend of mine had annoying rattle in his XJS a long time ago. Drove him mad so much so that he told Jaguar he didn’t want the car until it was fixed even if it meant taking the car apart. A 20 minute test drive and the technician came back and said he’d fixed it, it was a cassette tape rattling in the player (when you could eject it and leave it loose).

It’s really difficult to pin point rattles in such a small cabin. Noises that sound like they are coming from the front are actually coming from the back and vice versa. Check all the trim panels are fitted correctly as well.

Keep us posted.

Dan.

 

[BrianJ]

I've had one of those on my 718 recently. After a year of trying to figure out what on earth it was, discovered it was the Porsche badge on the key fob banging on the carbon fibre dashboard trim when going over certain types of bumps! You'd think it would be so ridiculously obvious to find, but it wasn't. Solution? - take the fob off the key ring and turn it round so the leather side faced the trim. Silence.

 

[ianthow]

It seems to be drivers side to middle from in the cabin, I've attached a quick video, it sounds much worse on the video but that my help identify it!

A bit of a left field suggestion here. I had a similar issue on the left side. My first reaction was something caught in an undertray or in the rear suspension at that side. It wasn't. I eventually traced it to a loose support bracket for the engine air intake ducting inside the rear wing (item 5 below). The support bracket is not shown anywhere in the parts list I have. It attaches to an inner skin of the rear quarter and supports item 12, which is a drain that feeds into the rear wheel arch. The support bracket was loose on the inner skin. I couldn't work out how to tighten or remove it. Instead applied some adhesive around it in the hope of some relief. It has been silent for over 5 years now.

On the right side you have the engine bay cooling fan (below). Given the fixings and brackets in there, that could be the source of the noise. There will also be cables and cable clips around there. It looks like access would be from the engine via the top engine cover (I have never had cause to dive into that area, so cannot help any more). There is other stuff hanging inside the engine bay in that area which could potentially have come loose to cause the noise.

 

[Motorhead]

Some useful suggestions there Dan, but just to add my own thoughts:

I think the first thing to do is to confirm that the noise definitely is emanating from the front rather than the rear, as Dan has pointed out. Sound is very directional, but phasing effects can cloud the issue in a small cabin space. I’d suggest that you go for a drive with someone else in the car who can listen while moving their head around.

Secondly I’d try to follow-up Marc’s suggestion to find a local MOT station with “shaker” plates which is a much more effective method of finding sources of play in the suspension than just using a pry-bar [just Google MOT garages with suspension shakers for your area].

Finally it sounds as though you’ve replaced all the bushes in the front suspension with the exception of the strut top mounts and the knocks that you describe are typical of those resulting from excessive wear in those mounts, so definitely it would be worthwhile replacing them. Plus you mention that you’ve had coil-overs fitted all round and presumably the spring rates are now higher than standard, so the stiffened set-up could be a contributing factor previously disguised by a softer arrangement, especially with worn components.

Jeff

 

[martin911]

Not quite a mouse with a spanner, but could it be something loose in or behind the dash?

I know some of the car play upgrades have a small module that sits behind the infotainment system (including the 997.1 PCCM+ unit). If one of those got loose, could it cause such a noise?

I have also had issues with the cup holder assembly in the past - the two screws that secure it into the dash were both loose and made it sound like the rattle was coming from the battery compartment.

 

[dan.hockey1]

I bought a chassis ear over the weekend, I whacked wires all over the place and went for a drive, after a hour or so I think we've narrowed it down to the wipers of all things! If you grab the drivers side wiper there play up and down on the spline it sits on (vertically). This appears to be tapping on connecting elements under the cowl, don't know if this is a common issue?

 

[JohnCRS]

That's great news Dan. I was going to suggest looking in the plenum in front of the windscreen and the wiper arms, battery and various other connections and ancilliaries.