Normal scuffing. This view is looking straight down on the edge of the Scotseal. The Bore-Tite will show some signs of scrapes and scuffing. That's normal. But nicks, scratches or metal particles are warning signs that something's amiss.

Make sure the hub bore is smooth and free of burrs.

Radial grooves across the seal. Here is another view looking straight down on the outer edge of the Scotseal. This time the Bore-Tite reveals a path that cuts across the full width of the seal. The mark doesn't have to be as deep and pronounced as this one is to be a leak path. Any continuous channel should be a suspect.  Most likely this leak is caused by a burr or damage to the inside surface of the hub.

The best way to avoid this type of leak is to make it a standard practice to inspect and clean the hub before every installation.  An emery cloth or a fine file should be used to remove any imperfections that could damage the seal.  On this design, the Bore-Tite (green area) is applied only across the contact surface of the O.D.. You will notice different applications on different Scotseal designs, but the interpretation of markings still applies.

Axial lines around the seal. If you find marks cut into the OD of the seal that run lengthwise, there are two logical explanations.  The seal could be the wrong part number for the application and thus might be spinning in the hub. Or, more likely, the seal was installed crooked (or cocked).  The marks on this seal clearly indicate it was not squarely seated in the bore. You can see the scratch line running from high on one side to low on the other. It is the most common cause of premature wheel seal failure.

The solution to this problem is training -- knowing how to select the right installation tool, how to use it and how to tell when the installation "bottoms out" solidly. CR has installation guides and posters to help with this task.

Suspicious markings. Occasionally you may come across a seal like this one that's been ground down to make installation "easier."  The mistaken theory is that by rounding off the leading edge, the seal will go into the bore easier. (So someone doesn't have to go and find the right installation tool?)

This leads to two results. Both bad. First it distorts the O.D. creating a potential leaker, and second it weakens the seal wall so that it's liable to come apart in operation.  Some innovation by technicians should be encouraged. This is not one of them.

Dents and dings. In this photograph, you're looking down on the Scotseal. The green Bore-Tite indicates the leading edge of the seal and the shiny metal is the air side.

The dents and bent casing you see, you can be sure, were the result of installing the seal without a proper tool (or the tool was damaged). Hammering on the seal to install it will always produce these telltale marks. Gashes and sharp indents indicate the use of a screwdriver or drift.  It is virtually impossible to seat a seal correctly with this type of installation method.

Polished packing. This damage is difficult to photograph, but if the packing is shiny, polished or has axial scratches, you can be quite certain that the seal was spun on the shaft. It's usually the result of a cocked installation. When the seal is installed crooked, the contact surface between the seal and the shaft is reduced, and the leverage of the large hub diameter increases. The seal spins. You could also see this damage if the wrong seal was installed.

It is always a good idea to double-check the part number.

Good news, bad news. The only way that the packing can be worn shiny, as shown here, is by rubbing against the bearing race. And the only way that that can happen is by installing the Scotseal backwards.

You can quickly and positively identify this damage and its cause. That's the good news. The bad news is there's a technician out there somewhere who needs some training in a hurry.

Banging the I.D. This is another installation problem, but it's not directly connected to the seal. A severely damaged I.D. indicates that the seal has banged into something pretty hard. The most likely culprit is the spindle shaft.

An eight ounce seal is no match for the forces generated by a 250-lb. wheel dolly.

A mis-adjusted dolly, a rushed installation or even a dirty shop floor are all potential causes.

If the packing of the seal -- where it comes in contact with the spindle -- is damaged or distorted, it's likely that someone tried to install the seal over a wear ring. The sealing surfaces of a Scotseal are inside the seal shell, so no wear can occur on the shaft.

The spindle should be cleaned and inspected before every installation. This inspection procedure will eliminate leaving a wear ring or any other contamination on the shaft.

Occasionally you'll discover a leaking seal that has a mysterious, tacky substance on it.

The most likely suspect is one of the old-timers who learned to "improve" the seal by adding a bead of silicone. With modern seal design and quality control, it's not needed. And, as in this case, will do more harm than good.