I have seen lots of videos on YouTube where people open sealed bearings for pulleys for their engine and add grease into the bearing, by removing the seal and replacing it.
I’m wondering is this a good idea? I thought that it was possible to “over grease” a bearing.
I’ve heard both ways so I just pop the seal to make sure there is grease in it and don’t add more.
Only an idiot does that kind of stuff.
The bearings are sealed which means they’re unserviceable.
It may stop a bearing from making noise, but it’s temporary.
Tester
Have you ever thought of not looking for problems where there are none ?
The first issue is usually when someone says- I saw/read this on the internet…
Back in the day, we only had the library, a group of friends or people at car shows as viable sources of information. Everyone had that friend or acquaintance that everyone knew wasn’t the sharpest knife in the drawer and would do questionable modifications or repairs. We all knew not to listen to “Jimmy’s” advice.
The internet changed all that. We now have access to virtually unlimited information from people all around the world. Unfortunately, that comes with an equal ratio of “Jimmys” that need to be sorted out.
Statistics suggests that an infinite number of monkeys pounding on an infinite number of keyboards should eventually produce a literary work of art. The Internet has since disproven that theory…
Be careful who you take advice from…
More chance of doing harm than good. The seals weren’t designed to be removed, damage them and lose all the grease, quickly.
Because lots of amateurs wanting their few minutes of You Tube fame, likes, and perhaps revenue obviously know soooo much more than the professional engineers that design vehicles and the professional mechanics experienced in servicing the vehicles. To each their own. 
Exactly my thoughts, If a sealed bearing is making noise the damage is already done. Just replace it and go about your day.
P.S. I used to do it with skateboard sealed bearings, but then again I was 12, and didn’t know any better.
I do that on sealed bicycle wheel bearings, just part of routine maintenance. But I wouldn’t do it on any bearings used in a car. Forces on bearings much greater in a car. Replacement bearings usually aren’t overly expensive.
Unsealed auto bearings a different matter. The wheel bearings on my truck are unsealed conical roller bearings. For those , as part of routine maintenance I just remove them, clean out the old grease repack w/new, reinstall, good to go. Same bearings for the past 50 years.
Yeah, I think the op was talking about the small ball bearings, not the roller or conical bearings. The sealed ball bearings are the same as the non sealed ones just a different number when ordering. The seal is just a plastic cover that snaps into place to prevent dirt from entering.
Before pressing the new ones into place and going through all the work of a reinstall, it is a quick check to make sure the factory didn’t miss putting grease in. No big deal. Doesn’t hurt a thing. But never found one without grease. If you add grease though you run the risk of too much that could pop the dust cover off.
In my youth I installed hundreds of various bearings in casters from rollers to pressed in sealed bearings. Not exactly my first rodeo.
Sealed bicycle bearing on left. Can be lubed by removing the black seal with a pen knife, easily replaced. Right is unsealed roller bearing for car.
Drive belt pulleys are cheap, replace them every 20 years.
There are people that insist pulleys must be replaced every 7 years, but only the ones protected from dirt and water by the timing belt cover. If these pully bearings have a short life span, shouldn’t the drive belt idler and tensioner pullies be replaced every 7 years?
I had to grease an AC compressor bearing. I didn’t catch it in time and it had started to make a faint scratching noise and after about 1000 miles it got to the point where I could identify where it was coming from.
The bearing is not meant to be removed. Doing so would require grinding and a press. I tried to remove some of the old grease and then I regreased it. It would make the scratching noise still until it warmed up. Now it seems to have gotten better. This is a 30 year old bearing where the grease became hard. It’s a double row bearing so I had to use an 18 gauge grease needle. After researching what kind of grease to use I just gave up and used my Valvoline high quality ball joint generic grease from the auto part store.
My chain saws have a small roller bearing by the clutch that should be greased once a year. I don’t know what kind of grease it is but Oregon sells the grease in a plunger just for that. About $8 but it is dang good stuff for those little overworked roller bearings. Green or blue color.
I have a Murrey riding lawn tractor, 1997 model. The blade housings have zerk fittings in them so I greased them every year. After the first 7 years or so, the bearings began to fail. I pulled the housings to replace the bearings and found out they were all sealed bearings.
Yeah there is a you tube on that. The old guy pulls the covers off and the greases the shaft. He says what good is it to pump grease in when the bearing are sealed?
My spindles have the sealed bearings but no zirk or way to grease them. So I leave the dust covers on. Sheesh I think I paid $60-80 a piece for new spindles so I just press new $4 bearings in instead. So I have a spare set.