Rear Suspension or drivetrain clunking noise at low speed

kyuan

My 2006 4*4 V6 is making noise at low speed from the rear wheel parts.
Ford dealer checked the suspension and drive axles, and claimed no mechanical problem. But the clunking noise will always be noticeable whenever I start running, and always clunk at low speed. There is no direct relation to bumpy road.
When I drive a few minutes, the noise will disappear, but when I park a while and start again, the noise will come again.
Is it due to loose parts, such as the axle? I noticed the tiny play at the rear left drive axle, but ford dealer denied the fact.
Did anyone meet the same problem before?

kyuan

Updates to the problem: the knocking sound is now isolated to the rear left wheel area. It only occurs when the vehicle starts moving from parking, and the sound is surely metal to metal click, which is to be triggered by slight shake of the wheel, not by speed bumper, but by smooth road with any wavy defects. The sound will go away in a few minutes, when the wheel parts are heat up. Apparently there is any gap causing the clunking, but which part is likely the culprit?

kyuan

Updates to the problem: the suspension system was checked again by another service workshop, and there is nothing loose found. Now it is clear that the clunking noise has something to do with the cold weather. When it is warm, the vehicle will not make any noise. But where was this hell noise from when it is cold?

stever

Have you ruled out the brakes then?

kyuan

Thank you for the reply. The brake pads and rotors (front and rear) are all new, less than two weeks old, and both of them were reinstalled by the original workshop twice (due to warranty). During the reinstallation, they all checked the brake system, and found no problem. Today, I had the brakes and suspensions checked by another service shop. They only discovered one loose pad at the front inner side, but the noise I'm discussing has been always from the rear. I just checked the sound definition from the web, the noise I noticed should actually be "rattle". It occurs only when the vehicle starts from sitting to moving. During the next period of driving, there would not be rattle noise, even when the vehicle has to go through bumpy road and sharp bumpers.
The rear shocks were also newly installed, Monroe Sensa light truck 31217. The installer claimed that their parts are absolutely innocent. I'm suspecting the differential, but Ford dealer claimed the driveline had been inspected, and nothing wrong found.
What should I do next?

thecardoc3

Some noises can be very difficult to figure out, and quite often the technician needs to be in the vehicle and with a second person to trade off the driving while the noise is occurring so that different angles to the sounds origin can be experienced. That of course means you probably need to drop this off overnight just for them to first experience the issue and then if they attempt a repair it may need another night just to see if they actually figured it out. A tool like Chassis Ear can be a big help. http://www.ebay.com/itm/Steelman-Products-97202-Wireless-Chassis-Ear-/111274480530 These microphones can be connected to different components and the listener can dial in which one(s) transmit the sound the loudest assisting in locating the source. Some noises though quite loud in the vehicle make take a couple thousand pounds of force and the component may only move 1/32 of an inch, if not less. There often is just no way for a technician pushing and pulling on things to generate enough force to produce the sounds in the bay or on a rack so a lot of this is a combination of intuition, experience, and patience. It's also noteworthy that the effort and time required to solve these kinds of problems is usually unpaid time for the technicians and since they can't earn a living by trying to help, well.....

kyuan

You are much appreciated.
Finally, I went back to the last workshop, confirmed with the old, experienced mechanics, that the differential is also out of question. From their point of view, no safety threat is surfacing. All I could do is to wait until the noise becoming continuous, then there must be some checkable signs from the parts.
On the web, there is someone blaming the new generation escape, that the new shocks are making noise. If this is true, I may have to go back to the workshop to physically check the new Sensa Shocks I replaced three weeks ago. Though the shocks were confirmed well installed by the last check, the quality might not be tested before the installation.
Up to now, I had visited three different workshops 5 times, and incurred a total cost around $1800 (including $300 worth parts, i.e. 2 sets of brakes parts, 2 rear shocks). It is really a good training to me. I was forced to learn the structure, part names of the vehicle and different procedures of the workshops.
And since the noise is what I have to track, it keep me in good alert, and keep driving me to learn. In this sense, it is not a bad thing at all. I may consider to buy a set of these ears to listen and record!
One big lesson to me, I should have chose only one workshop, not to just check their price and ads for short term benefits.
Thank you again!

kyuan

Could the function of nitrogen filled shock absorber really be affected by cold weather?

kyuan

I carefully observed many times, both inside and outside of the vehicle, and found that the louder rattle noise is likely from the upper mounting area of the shocks. And then, after a few minutes of driving, when the louder noise went away, some faint high frequency clicks (thin metal parts) would come when the vehicle hit any sharp bumper. So, I decide to check the new shocks, both for function (as one of shock absorbers seemed not responsive to the first a few shocks, not until it was compressed several times did it start have normal response), and the mount torques.

kyuan

The problem solved!
Today, I went back to the service shop, who installed the shocks for me. They replaced the two shocks with completely new ones, as I monitored the unpacking of the new orders.
The noise went away during the road tests. I parked 20 minutes under the snowing weather first, repeated parking and starting 5 times, no noise any more.
Clearly now the noise was from one of the shocks.

stever

Great - thanks for all the updates!

kyuan

Thanks Jesus, He give me the power of patience and tolerance.
I can now differentiate noise from different parts, especially from the suspensions.
Next step, I should learn how to listen to the engine.

kyuan

Updates to the new shocks.
The genuine Monroe shocks are doing well up to now on my Escape. The extreme blowing snow weather today did not make them shrinking.
Thanks God!

Steichner

Kyuan, This is amazing! I have a 2004 Ford Explorer and have the EXACT same issue! I heard the same noise under the same circumstances. I’ve had all 4 brakes, rotors and pads replaced, sway bar fixed, and replaced the rear differential…cha-ching…only to have the same issue. The garage is sick of me and claim there is abso,Ute,y nothing with the car and they cannot hear a noise …I even parked it there overnight so they could hear it upon 1st start up. I am going to take my car somewhere else and ask for Monroe shocks. I no longer trust the garage that did all of the previous work. Wish me luck! Thank you so much for your post.