Sealed bearings are serviceable ...

I just bought a new sealed bearing for my idler pully. First thing I did was pop the little rubber seals off and look inside. There was almost NO GREASE in there, and it didn't apear to be the best quality grease either. I wiped out the old grease that I could get a rag on, and packed it with some high-quality "moly" grease ... the kind made for CV joints.

I really think this will make it last longer. And from now on, any time I buy "Sealed" and "pre-lubed" bearings, I'm going to do this.

To pop off the seals, you can get a knife tip inside the seal where it hits the INNER race. get the tip under it and pry upward gently. The seal will pop right off and not be damaged at all. It pops right back on again with just a little hand pressure.

The idea is good, but according to what I've read in literature from ball bearing manufacturers, you need to watch out for two things. First, do not overpack a sealed bearing because the grease will just churn and not do its job. It may actually cause the bearing to overheat and lose its lube too fast. Remember that grease is just oil with some gunk in it to make it not flow out. A tiny bit of oil is all it needs at a time.

Second, you might not want to use moly grease, or any grease with solids in it such as graphite, because the solids will get under the balls and actually impede the rolling action (this comes from an old New Departure handbook which predates moly, but specifically warns against graphite). The requirements for CV joints are quite different, where the clearances are greater and the added moly protects against impact.

Just a small amount of light grease is proper because that little bearing turns 1000x faster then a u-Joint.

In my Segment of Aviation we had an enormous bearing that failed several times and took some lives, so we got a lot of info on these bearings and bearings in general. BUT THIS IS AVIATION, SO EVERYTHING MIGHT NOT CARRY OVER.

But, what Matthew said is exactly what I learned. Too much grease is bad, it will hamper the heat transfer of the bearing and just a little is only needed.

Fresh grease always helped as well. In our case, the seals on the bearing was designed to release excess grease, and too much grease was better than not enough, because, even though excess did impede heat transfer, it just heated up the grease and it flowed out of the bearing and seal to leave behind the proper amount.

Grease also gets complicated, there are many different greases and many specific factors in bearings that dictate the grease to select. What Matthew said about grease with solids makes a lot of sense, the contact surfaces on bearing are super precise and under tons of pressure, I could see solids in the grease coming between the super precise contact surfaces and galling, nicking or denting the surface, ever so slightly and micro-scopically, but enough to add up and start to degrade the bearing.

As well, some greases have incompatible bases and if you mix them they will breakdown each other and you'll end up with a poor contaniminated grease.

I lean toward getting a quality sealed bearing and then not messing with it, adding grease may do more harm than good.

Rick Anderson said:

I lean toward getting a quality sealed bearing and then not messing with it, adding grease may do more harm than good.

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Me too. Sealed bearings are sealed for a reason, they don't need more grease. The grease in there is fine, it's a synthetic stuff designed to work with the bearing's high operating speeds and therefore, temperatures.

Realistically, how much extra life do you expect to get out of an idler pulley bearing? It's not like they go bad on a regular basis anyway...

Thanks for the responses. Lots of good info that I didn't know about.

I'll make sure I don't have excess grease in there, then I'll install it and keep an eye on it to see how it does.

It's a cheap bearing, so I'll use it as a "test" of the moly grease.