Intermittent rear of car pulsation

LEBBING

MEMBER
2001 LINCOLN TOWN CAR
4.6L
V8
2WD
AUTOMATIC
89,000 MILES

I have the same problem as two other members but I found no good answers. The 2CARPROS members were ROBBOB3871, 2001 LTC @ 61000 miles and KHUT, 2003 LTC @ 89000 miles.
I have a like new car listed above with 89,000 miles that just developed an intermittent pulsation that only comes from the rear of the car. The pulsation feels like road edge rumble strips or activated anti-lock rear brakes. The pulsation occurs for only a second or two then stops and reoccurs every few miles or so. At first the pulses were very fast then the rate slowed and they occur every few miles. The car has newer tires, air suspension springs and brakes and the highway was smooth at about fifty five to sixty mph. The ride remains very smooth all of the time. I have never heard of this problem and hope someone has an answer.

1 Reply

CARADIODOC

MECHANIC
33,871 POSTS

Thank you for providing plenty of information. I suspect this problem is related to age, not mileage. Specifically, I am suspecting it might be related to dry-rotted rubber bushings or isolators. The Air-Ride Suspension pump is in the engine compartment, but there are actuators on each air spring. I wonder if you are hearing or feeling an actuator pulsing. There is a switch on the left side inside the trunk to turn the system off. You might want to do that then drive the car to see if the symptoms stops occurring.

If this is something you can hear, there is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.