A little question regarding wheel bearings on Subaru's. A friend of mine has a Forrester and about three months ago the rear wheel bearings had to be replaced. When talking to the mechanic of the local Subaru dealer he told me that it was a common problem and that Subaru had re-designed their wheel bearings.
Three weeks ago again a(new,5000 km's)rear wheel bearing went to heaven, and after making arrangements to get it fixed,and asking some questions with the previous story in mind, the Subaru rep told me that it wasn't our fold that the bearing didn't make it to it's expected life expectancy. Prior the operation !!!!!!!
Are there any other Subaru drivers out there that had the misfortune of replacing wheel bearings on (to) a regular basis.
Be sure any bearing replaced is the roller bearing type. Special press type tools are required to do the job and can not be preformed with a vice and hammer home shop as often the bearing carrier will be distorted/damaged causing repeated failures. eddie
It's a common problem with some cars. Do a search for "Subaru wheel bearing failure." Lots of stuff pops up.
Two thoughts: first--Subaru has issued TSBs about the problem, substituted roller bearings for balls, claimed ineffective grease seals allow water into the bearing, and even come up with a "new" bearing. Subaru's claim is that the bearing housing can become distorted thru improper (including factory) installation and assembly. You should find the TSBs in the search I mentioned above. I understand the failures are primarily with ball bearings, and replacement with rollers has been successful for many owners.
My second thought is a bit more controversial. Subaru claims the new bearing is factory packed with the proper amount of grease, and NO grease should be added at installation. We've discussed this before, and I DON'T agree. In close to 40 years of packing/replacing wheel bearings, I've NEVER seen one that was properly greased in shipment. Many even come with warning tags to clean out the packing grease which is just an anti-corrosive measure and grease properly at installation. I've had one wheel bearing failure on my Subie (factory) and inspection of all the bearings on the car prior to that failure indicated they were NOT sufficiently greased. The one that failed was virtually dry (red rusty dust evident) when I got the car at 209k miles. IME that's NOT normal. I've also (so far, at least) never had a bearing I installed fail, either from wear or entry of water, but they were all greased to the hilt. I'm sure Edward Hayes will weigh in that too much grease is bad for the bearing and seals. I usually agree with Eddie, but on this point, I feel that's bunk. Too much grease may bleed out a bit and need to be wiped off, but it won't harm the bearing (witness bearing lubing systems for boat trailers where you pack the bearings FULL with a grease gun!) If you read all the posts when you do the search, you'll find several Subaru mechanics have weighed in on various fora concerning this grease issue, and it seems they agree with me that the factory grease is inadequate. But YMMV.
So, while there is a possibility of improper installation causing problems, the installation of bearings at either the manufacturing or repair level is NOT rocket science, and I'd suggest Subaru's insistence on using ball bearings is a part of the problem, but the lack of proper lubricant is THE biggest problem. Well greased, carefully installed, rollers make sense to me.
I will take one step back on this one Rick since I have not seen or opened a new Subaru ball bearing. When one buys a bearing from a Subaru dealer that has I warning the bearing has sufficient grease and NO additional grease should be added I took that as gospel. Apparently some bearings (out-of-the -box) don't have the proper amount of grease. I stand by my opinion that bearings can be over greased to the detriment of the seals and bearings. Boat trailers are pressure packed to keep from sucking in water when the boat is launched and typically fail with only a year or two of use. My experience with ball bearings on my old Porsches is that balls are good IF the bearing carrier design correctly and the bearing is installed correctly. I never had a rear wheel bearing fail me in I'm guessing 300,000 miles. My 2000 Forester with balls (I checked VIN number) is still going strong at 62,000 miles. Thanks for the input Rick and as I said I take a step back on the lube issue. eddie
A word of caution based on experience- overfilled grease lubricated antifriction bearings can overheat, due to churning of the grease, and fail at quite modest rpms unless excess grease is discharged automatically. I doubt whether Subaru incorporate a grease discharge valve on their wheel bearing housings- this would be clear from the service manual, which I don't have.
Forester wheels at 70 mph rotate at between 920 and 950 rpm and I have a gut feel that this may be getting into the danger zone for long trips at interstate speeds
If there is no discharge valve, before running with an over filled bearing housing I suggest discussing this with customer service people at a bearing manufacturer- eg Torrington or SKF.
This is in agreement with what Eddie's been trying to tell me!
Since my experience is different, and I may have to stand corrected, please let me ask a question: when you say "overfilled," does that mean the area in between the bearings was completely filled, too? IIRC, every wheel bearing I've worked on was mounted in either a hub or a housing that had "overflow" capacity between the bearings at either end. Only enough grease is supposed to be put in that area to prevent corrosion. That way, even if the bearing itself is WAY overgreased, the excess can bleed or "discharge" into that area. The front hubs of my Subie (ball bearings) have such an overflow area, and the rears (rollers in a cartridge) also allow some expansion. I'm sure the designs are similar on even the newest bearings. So if that's what you mean by a "discharge valve," then, yes, there is one.
Rick- regarding the effect of more or less grease in and around an antifriction bearing- there is no general answer because so many factors are involved.
The problem with overgreasing is that during operation, churning may heat and soften the grease, which then flows to form a pool at the bottom of the bearing housing. If the pool is deep enough for the rotating parts to continue the churning action, then heat buildup may continue, and the bearing temperature increases to an equilibrium level which depends on the heat dissipating capacity of the housing and shaft. If the conditions are bad enough, the grease may break down and early bearing failure can occur.
Thus, if the bearing only (not including the housing) is filled with grease and the housing has a suitable shape and size, IMO the bearing life will not be reduced. If the housing is filled with grease, all bets are off. If the free space in the housing is negligible, even a relatively small amount of excess grease may cause trouble.
I bought some Valvoline Synthetic a couple of years ago to do my CV joints on the recommendation of someone here. (I'd used the "special" grease that comes with the boots several times before.) Yawn. The joints were NOT clicking before thorough cleaning, repacking and installing new boots. Within a month, both sides WERE and the right side failed shortly thereafter. Could be pure coincidence, since the joints were original and the first failure occurred after 300k miles, but I wasn't impressed.
I used the rest of the can when I replaced my front wheel bearings, but they've only got 20k miles or so, so can't comment on whether the stuff's any better in that app than conventional hi-temp wheel bearing grease.
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