I searched for all sorts of keywords related to this issue in this site, and others, and i couldnt come up with anything, so hear it goes.

i have a 2004 XJ8 with 57k miles and last night it rained pretty hard while the car was parked outside. im not sure if all that information matters but maybe its relevant.

so when i hit normal lumps and bumps on the road the sound happens on the rebound (when the car is pushing back up) or i can make the car produce the sound continuously when turning left and im compressing the suspension on the right side of the car. at first i thought it was a faulty connection to the speaker because it had a staticy sound quality to it. but then once i turned the radio off and listened more carefully i noticed it had a more sucking/gurling sound quality to it also. (rain water in something?) i turned off both the radio and climate control system and the sound is very repeatable when hitting bumps and turning a hard left. no warning lights, and all other performance of the vehicle is normal (i mean incredible, my god this car rides smooth )

is this a possible air suspension issue? are there components inside the cabin by the footwell of the passenger area? any help would be appreciated.

 

you might start with checking the cabin filter in the engine bay. The housing collects leaves, clogging the drain tube and they will fill with water.

Start there as that is the simplest and you indicated a hard rain.

Check both side for good measure. They are in the engine bay in the back corners, against the firewall. Easy to see the boxes and remove the covers.

 

ill have to check into that later tonight when i get to my car.

 

Sean is dead right. My 2002 SE had the same problem in hard rain. The bonnet shape funnels the water into the 'drain', but the drain is blocked! Use a heavy wire or old speedo cable to clear the outlet.

 

i drove home yesterday from work and it made the interesting sound a few more times but that was it, like the water was all gone from that area. but i will certainly remove all debris and clean out the drain as best i can as soon as possible. thanks for the help.