Strut Leakage versus Weepage: Understanding the Difference

Learn the Difference Between Strut Leakage and Weepage

Quick Summary:
Not every oily spot on a strut means the strut has failed. In fact, perfectly good struts can show light traces of oil. That’s known as a weep, not a leak. An oil weep from a strut—a light film or dried residue—is normal and does not require replacement. To help you avoid unnecessary repairs, I’ll explain exactly how I evaluate an oil leak on a strut, the difference between weepage and leakage, what causes strut failure, how to inspect your suspension correctly, and when replacement is truly needed.

Article

Every strut on the road is filled with hydraulic oil and pressurized nitrogen gas. The piston rod passes through a precision wiper seal that keeps the fluid inside. But with every bump and every compression, the piston moves through that seal, and microscopic traces of oil cling to the rod. Over time, that residue collects at the top of the tube. This oil residue is called a weep, but some dishonest shops call it a leak. See this difference between a strut weep and a strut leak in the image below from Monroe.

Notice the difference between a leaking shock and a weeping shock

Why a strut/shock weeps and leaks

Look at the image to the right. It shows the three seals inside a strut/shock. As the strut piston moves up and down, the Teflon buffer seal and the twin-lip main seals prevent oil and gas from escaping from the strut. The wiper seal at the tip wipes off any oil that got past the first two seals.

Over time, the seals wear and a small amount of oil escapes. This is the weep stage, and it’s not a reason to replace the strut. However, as wear increases, more oil leaks out and drips down the strut’s side. At that point, it must be replaced.

For more information on shocks and struts, see this article at Brake and Front End magazine.

If your strut is leaking—meaning oil is actively escaping at a rate that affects performance—that’s a failure. A leaking strut no longer functions properly. It can’t effectively dampen the oscillations of your springs or maintain proper contact between your tires and the road. This compromises safety, as it can lead to longer stopping distances and reduced control of your vehicle.

Can I keep driving on a leaking strut?

No. Once a strut is leaking, it’s no longer effective at controlling the vehicle’s suspension.

A leaking strut can increase your stopping distance by as much as 12 feet from 60 MPH, which is a serious safety concern. A failed strut means less control over your vehicle, and that’s something you can’t afford. Get it replaced as soon as possible if you notice a leak.

Get it replaced as soon as possible.

This is what a leak looks like.

See this post on when to replace shocks and struts

©, 2020 Rick Muscoplat