Why are my strut mounts failing

Put new struts and strut mounts in summer, the both strut mount failed causing the strut to come through the hood a few months later. Today I re[paced the strut mounts only this time and after 10 miles, these are starting to fail. I can see the strut nut move up and down with metal shavings around.

What am I missing?

My car has 191000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
The shoulder on aftermarket struts at the top of the piston is sometimes designed such that you have to put a washer or washers underneath the strut retaining nut in order to properly tighten the piston to the mount. Also, you have to be sure that you have applied the correct torque (with a torque wrench) to the retaining nut, otherwise the piston will move relative to the mount and the back and forth pounding will cause the kind of failure you are seeing. Also, check to be sure you are not missing any parts in the assembly. The only way to be sure of a problem free installation is to use OEM (dealer supplied) genuine parts. It is possible that your issue is, in part, caused by an aftermarket part/design that is just not appropriate for the application. To get this resolved, I recommend you request strut inspection/replacement and in the course of that consider just installing the OEM parts that are guaranteed to fit and work on your particular vehicle. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

The most common symptoms of a bad strut mount are squeaking noise when turning the steering wheel at low speeds or knocking, banging, clunking, or popping noises when hitting speed bumps or irregularities on the road. Diagnosing top strut mount problems is recommended as soon as you notice symptoms.
A common cause of engine mount failure is age and wear. Engine mounts are typically made of rubber, a material that is prone to wear over time and may lose its elasticity and, as a result, lessen its function to your engine. Age and stress can cause small cracks in fluid-filled engine mounts that can lead to leaks.
As a rule, strut mounts are not wearing parts.

Due to their design and function, they are made to last for the entire life of the vehicle.

Some shock absorber manufacturers say you should replace them at 50,000 miles, but that`s more for their benefit than yours. Having the shocks and suspension parts inspected at 40,000 or 50,000 miles, then annually after that, is a better idea.
Can I drive with a damaged strut? No. It needs to be repaired as soon as possible. A strut works by absorbing the bounce of your car driving over bumps in the road.
There is most likely nothing wrong with the replacement shock or strut, but a metallic clunking noise typically indicates loose or worn mounting hardware. A loose mount can allow movement between the bolt and attaching parts, while a mount that is worn can cause the shock/strut to move up and down.
Can I drive with a damaged strut? No. It needs to be repaired as soon as possible. A strut works by absorbing the bounce of your car driving over bumps in the road.
As a rule, strut mounts are not wearing parts.

Due to their design and function, they are made to last for the entire life of the vehicle.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Why are my strut mounts failing
ANSWER : The shoulder on aftermarket struts at the top of the piston is sometimes designed such that you have to put a washer or washers underneath the strut retaining nut in order to properly tighten the piston to the mount. Also, you have to be sure that you have applied the correct torque (with a torque wrench) to the retaining nut, otherwise the piston will move relative to the mount and the back and forth pounding will cause the kind of failure you are seeing. Also, check to be sure you are not missing any parts in the assembly. The only way to be sure of a problem free installation is to use OEM (dealer supplied) genuine parts. It is possible that your issue is, in part, caused by an aftermarket part/design that is just not appropriate for the application. To get this resolved, I recommend you request strut inspection/replacement and in the course of that consider just installing the OEM parts that are guaranteed to fit and work on your particular vehicle. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Are the motor mounts touched during a tune up? When are the motor mounts touched?
ANSWER : There is nothing in a basic tune up that would require loosening or touching the motor mounts. If the motor mounts are in fact loose, they could potentially cause damage to the axles if the motor were to shift enough while driving; however, this would take time and there would have been a very distinct vibration and clunk that you would have very likely noticed while driving. I would recommend having a certified technician, such as one from YourMechanic, come take a look at the car to properly diagnose and repair your motor mount problem.

How many transmission mounts are there in an sl55 amg and are they the same mounts as the front engine mounts?
ANSWER : Sometimes the way they are labeled is confusing. In a car like yours, where the engine is mounted front to rear, there are three mounts. The two in the front on either side usually look similar to each other, but not identical. The rear mount at the tail of the transmission will look entirely different and makes the third point of the plane. Many times the transmission mount will be referred to as a rear motor mount in parts literature. If you need too have your mounts inspected or replaced, you can contact Your Mechanic.they can send a technician to your home or office to replace your motor mounts right there on the spot.

Are strut mounts typically replaced when you do new struts on front end? Quoted $700+tax for both – not including alignment. High?
ANSWER : Hi there. Were the mounts quoted in the estimate? Was a strut assembly quoted? If the answer is no to these questions, then the strut mounts were not quoted. However, the strut mounts on this vehicle are pretty much just a rubber cushion designed to aid in the absorption of road shock. There are many aftermarket brands that offer complete assemblies at reasonable prices. Installation and part prices can vary from one repair facility to another. I suggest acquiring additional estimates and comparing the pros and cons of each. Was an inspection performed that determined that the struts are in need of replacement? What was the diagnostic process or reference specification? As a former Toyota Master technician I can tell you that Toyota has a specific criteria measurement for leaking struts and shocks; some leakage is normal, but if the fluid is all the way to the bottom of the shock tube it is in need of replacement. Your Mechanic has several available technicians that can assist you with a suspension inspection and a strut replacement.

What is cost to neutralize motor mounts, I switched out front mount but now it vibrates off of frame
ANSWER : I believe you need to replace all of your mounts. You are saying it is touching the frame, so I would suggest the rest of them be replaced also. You may also look around and see if you have anything obstructing the fact that it isn’t sitting properly. I hope this helps with your issue.

Banging noise in rear going over bumps, mechanic said struts and struts mounts are fine.
ANSWER : Considering that this vehicle has independent rear suspension, it is possible that a rear ball joint, toe adjuster, or control arm bushing has some play. This will cause a noise very similar to what you are hearing. It is also possible that your wheel could be loose. I would recommend having a steering and suspension inspection performed by a qualified professional to determine what parts have failed. I would strongly recommend having any faulty parts replaced and an alignment performed as soon as possible as this could result in a safety issue.

I have some sqealing and groaning/grinding on driver side by the strut mounts. It happens when backing up left or right and when driving slow.
ANSWER : If the struts and mounts both look ok and passed the bounce test, you may be looking at a CV joint or bearing. Inspect these components and check for wear and any visible damages. There is also a possibility the brakes could be making the noise. If they are worn down, or misaligned they will make a grinding noise. The groaning may be a sign of metal on metal. Another attempt would be to have someone else recreate the issue while you listen and try to find the location of the noise.

To avoid any unnecessary repairs, you should have a certified technician, like one from YourMechanic, inspect all of the suspension and wheel assembly components in that location.

Rubber mount or hydraulic mount
ANSWER : Engine mount and motor mount are completely interchangeable terms that refer to the identical component. There is an additional mount though and that is the transaxle or transmission mount. That mount is important, too, in minimizing vibration. For ordinary passenger cars, there are no choices as to mount type (i.e., hydraulic versus solid rubber). Vibration at idle can have multiple causes so you should be sure that the mechanic has provided you with an accurate diagnostic, accompanied by reasoning as to why the mounts are the cause of the vibration versus other potential causes.

In your circumstance, where you are trying to resolve a vibration issue, it is recommended that the original OEM mounts, as designed and manufactured by Honda, be used as the replacements. If you use aftermarket mounts, and the vibration issue persists, it will literally be impossible to rule out the aftermarket mounts as a "new" source of vibration due to a defective design. To save yourself headaches, and further diagnostic problems if the vibration persists after replacement, if you suspect motor mounts are bad, replace with OEM mounts only. Obviously, the Honda mounts are going to be more expensive though. After replacing the mounts, if the vibration issue persists, the problem is either engine running condition, or a mechanical or balance issue with the engine, for example the harmonic balancer. Before doing anything, I would ask the mechanic who told you the mounts are bad what his reasoning is. If he has no credible explanation, you should get a diagnostic FIRST before replacing any parts. If you are in need of a diagnostic, please use YourMechanic’s vehicle engine vibration diagnostic service page. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.