84 325e: when you 1st take off, there's a heavy loud knocking from underneath the car, in the area behind the passenger seat. Once you reach 20-30 mph, it stops. Thanks for your help..

On my 2001 van I can just reach under the rear of the seat and pull a metal bar back to release the seat while it's still upright. If you don't have a bar, feel around underneath for a wire that will pull the two release levers up.

loud knock and for how long

is it a diesel or petrol

broken engine mount

loud tapping is tappets ..should go away once oil reaches top of motor
water pump or bearing something running off drive belts

if high milage engine
a loud knock at engine revolution or half revolution
big end bearings or
piston slap or gudgeon wear

If passenger side is dry it would point to a problem with the door seals on the drivers side either a door or sunroof if you have one. If there is that much water you could sit in the car, have someone use a garden hose or pressure washer on the door and sunroof to see where the leak comes from.

timing could be off or try higher octane gas

Take the whole seat out of the car. Take it to a shop that does car upholstery.

Did you transport a box or heavy object on the passenger seat?
The weight sensor (part of air bag system) detect a heavy object on the passenger seat.


With key on and engine running,clear the passenger seat ////// buckle then un-unbuckle to clear warning.

Also check the weight sensor and buckle connector.
Car wash clean can accident disconnect (or damage) this connector during vacuum.
======== Also inspect the pass. buckle opening for dirt.

Engine Control Computer is located in the front seating area, passenger side, under dash, mounted behind kick panel

The seats have adjsutable levers for forward motions in which instance makes spaces at passengers area behind the front row seatings. Also,, the levers on the sides of the seats should provide shift movements to the back passenger seating rows to acquire drivers area seatings. Pressing the levers along the seating as adjustments should provide enoung accessibilty to objects that may have fallen underneath to floor of car. Refer to the vehicles user seating guides on how to manuver the seatings along with the levers provided.

I have a 1993 ParK Avenue, the original owner said that when she purrchased the vehicle new in 1993, she has always had water getting into the trunk, I found water in the passenger rear floor and I assume it is through the trunk, I had water in the trunk, I drilled holes in the trunk , also in the floor of the passenger area, Yesterday I vaccuum the car and the passenger area was dry, I think a little water may enter the trunk but it will drain before it reaches the interior.

the water is usually from the evaporator located behind the dash under the passenger seat area