Just A Touch Of Oil: SureTrack Community Fix

Intermittent noises are hard to reproduce and therefore hard to track down, especially if they only happen while driving. SureTrack community member Jeffytune had a Cadillac Escalade in the shop that would sometimes make a loud buzzing noise after driving over a bump or dip. They posed the question to the community, and with the help of fellow community members ericsautomotive and jbsprintcar, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2005 Cadillac Escalade ESV 6.0L

Title
Loud noise after driving over bump, repaired axle seal.

Complaint
Customer complains of loud buzzing sound after driving over a bump or dip. Stops happening after a while.

Diagnostic Steps Performed/Parts Replaced
Test drove vehicle to verify complaint. When driving, more often when first started cold, and you drive over a bump or dip, the vehicle will very loudly buzz. More so at slow speeds. We can not get it to do it in the shop on the lift, it has to be moving. From the driver seat, it sounds like it was from the left front, when walking next to the vehicle, it seems to be more in the left rear. We first thought it might be the ABS pump, we unplugged both the pre pump and the main ABS units, it still does it. We then thought it could be the air ride compressor, we unplugged it and still the same. We first tried to remove the fuses to the ABS and the air ride, then we physically unplugged them, and still no change. After the vehicle is driven enough to warm it up, this issue stops. When it does it, it is loud and buzzes the floor, so it seems like it’s right under your feet. I read the TSB on the wheel bearing issue for the ABS, but with the units (both of them) unplugged, I can not see how they could.

Cause
After many tries, we finally got it to do the noise on the rack by power braking and hitting the suspension with a rubber hammer. We hit the bottom of the left rear tire, and the buzzing started, then as the tire stopped, the buzzing stopped. We pulled the tire off and the brakes looked fine, we then pulled the rotor off and there was the issue. The axle seal was leaking a small amount of gear oil on to the one piece park brake shoe. You could not see any gear oil on the backing plate (rear disc with the one-piece parking brake shoe) and the shoe was the source of the noise. This explains why as you drove it the noise would go away and it would only do it cold.

Correction
Replaced the axle seal and parking brake shoe. Cleaned up the inner rotor and backing plate, Test drove vehicle and it no longer makes the loud buzzing sound.