1998 XK8 convertible has developed knocking like rattle in dash when hitting even minor road bumps. Irritating! Appears difficult to get behind dash to investigate. Just started. Something come loose or broke all of sudden. Anyone had similar issue?

 

Often times the noise originates from the plastic HVAC vents as their foam backing in certain spots long ago decomposed and blew away. Some owners have had success in quieting the noise by stuffing various thicknesses of weatherstripping into those areas to serve as a buffer between the vent pieces. It could also be coming from where the dash edge bumps up against the bottom of the windshield. Again, appropriate-sized weatherstripping may make the area quiet again....

 

... Or it transmits from your shocks when the upper mounts give up the ghost.

 

Thanks Jon,
By you saying "blew away", are you indicating the behind wiper guard? The knock seems to be in the area near the interior vent section. Car has always been garaged, purchased new in Atlanta, never in snow or ice and currently has <53k, but at 20 yrs of age decomposition is a possibility.

 

If the rattling is indeed coming from your HVAC vents, the deteriorated insulating foam was in the joints inside the HVAC vents and ducts. It gradually broke down and blew away INSIDE the vehicle as the climate control system did its job and blew conditioned air throughout the cabin exactly as designed. A very common occurrence in all old vehicles these days. The insulating foam in my 20-year-old Dodge Ram's HVAC system gradually blew away more than a decade ago, but the system continues to function normally without any annoying rattling. Now that I have typed those words, I will not be surprised if it rattles on me the next time I drive it....

 

I appreciate the insight. Best with the Ram. I have an 07' 1500 "ThunderRoad" quad cab. Great truck!

 

One more time for the new guy.
Please look at all the TSBs for your car and many questions will be answered as Jaguar is ALREADY aware of many issues.
All the info is on this forum or Gus has it on his site (jagrepair).

bob

 

so in my car it is the speaker grills that rattle now and then, the grills right in front of you to the right and at the other end of the dash, they face upwards and are colored like the dash, they are plastic and held in place with some worn rubber type bits, try touching them when you are driving to see if in fact the noise goes away?

 

Jaguars have had the squeaks and rattles that have their own fault diagnostic bulletins.
Here are a few more.

bob

 

they is almost nothing in the dash that causes rattles. BUT, there are a lot of suspension noises that get transmitted into the braces from the upper shock towers to where they bolt up to the firewall. If youre a betting man you would bet on the dash and you would be wrong. The noise is virtually NEVER in the dash but sure as hell sounds like it. Go after suspension inspection