The short version
- The lip faces the grease. Fitted backwards, the seal pushes lubricant out instead of holding it in.
- Note the depth before removing the old one, because flush is common but not universal.
- Lubricate the lip before fitting. A dry lip overheats the moment the shaft turns.
- Never drive on the seal face with a punch or drift. Use a driver that spreads the load.
Wheel bearing seal replacement is a five minute job with one decision in it that people get wrong, and getting it wrong looks fine until grease appears on the backing plate.
The decision is which way round it goes.
Which way a wheel bearing seal faces
The flexible lip is shaped so that pressure from the wet side pushes it harder against the shaft.
Turn it around and the same pressure lifts it away instead. The seal then leaks under exactly the conditions it was meant to handle.
On a wheel bearing the wet side is the grease, so the lip points inward toward the bearing.
Most seals have an open back facing the fluid and a closed front, often carrying the part number.
The number and the smooth face go outward. If you can see the spring inside the lip, that side goes toward the grease.
The other directional parts of the job are on the orientation page.
Wheel bearing seal replacement: before you remove the old
One measurement that saves a guess later.
Note how deep the old seal sits. Flush with the hub face is the common answer, but some designs sit recessed against a shoulder.
A seal driven past its shoulder can block a drain path or sit off the sealing surface on the shaft.
Once you have removed the old one, that information is gone unless you wrote it down.
Getting the old seal out
Three methods, in order of how much damage they risk.
A seal puller, which hooks the shell and levers against the hub with a protective foot.
A screwdriver with a rag under it, which works but is how bores get gouged.
Driving it out from behind, if the design allows access, which is the cleanest of the three.
A scratch in the seal bore gives grease a path around the outside of the new seal, which no amount of correct fitting fixes.
That is why the rag matters, and why levering against the soft hub face is a bad habit.
Fitting the new wheel bearing seal
- Clean the bore completely, and inspect it for scoring from the old seal.
- Check the shaft surface where the lip will run, since a groove worn there defeats a new seal.
- Lubricate the lip with the grease it will work in, before it goes anywhere near the bore.
- Start it square by hand and confirm it before applying force.
- Drive it with a proper driver that contacts the outer rim, to the depth you noted.
A driver that spreads load around the full rim is the same tool family as a bearing race driver, which is on the race driver page.
If the seal has to pass over splines or a threaded section to reach its bore, wrap that section in tape first.
A lip nicked on the way in leaks immediately, and nothing about the finished job shows it.
The surface the seal runs on
Worth checking properly, because it is half of the sealing pair.
A shaft or spindle that has carried a seal for years often has a polished groove worn into it. A new seal riding in that groove leaks straight away.
Repair sleeves exist for exactly this, and fitting one is far cheaper than replacing the shaft.
What the seal is up against generally is on the seals page.
Afterward
A trace of grease appearing once and stopping is a normal purge. Grease that keeps returning means the seal is not doing its job.
Telling those apart is on the escaping grease page.
Common questions
Which way round in a wheel bearing seal replacement?
The lip faces the grease, meaning inward toward the bearing. The closed face with the part number faces outward.
What happens if I fit it backwards?
Pressure lifts the lip away from the shaft instead of pressing it down, so the seal leaks under the conditions it was meant to handle.
How deep should it sit?
Usually flush with the hub face, but not always. Note the depth of the old one before removing it.
Do I need to lubricate the lip?
Yes. A dry lip overheats as soon as the shaft turns, and that damage happens in the first seconds.
Can I drive it in with a punch?
No. That deforms the shell and cocks the seal. Use a driver that contacts the outer rim evenly.
My wheel bearing seal replacement still leaks. Why?
Usually a scored bore, or a groove worn into the shaft where the lip runs. Both defeat a correctly fitted seal.
Can I reuse a seal?
No. Removing one distorts the shell and the lip has already taken a set. Fit a new one every time.