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1998 Legacy Outback Wagon - unknown wheel issue

Very new to the forum concept, had no idea where to file this question so here it is. Thanks in advance for your time and feedback.

I recently purchased a 1998 Subaru Legacy Outback wagon, with a 2.5L engine and 5-speed manual transmission. I bought it at about 149,000 miles and have driven it a couple thousand more in the month that I've owned it. Considering its age it appears to be in fine running condition, except for the fact that it's a rustbucket, and a baffling sound that seems to be coming from the rear driver's side wheel or the surrounding area. A coherent description of this sound eludes me. It doesn't sound like rubbing or grinding exactly, more like metal loosely revolving inside metal, almost like a labored fan spinning, but less choppy than that. Or like a ball of sand spinning around inside a hollow metal donut. (I -really- apologize for the nonsensical description, finding the words to describe it has truly been plaguing me.) I can't seem to sense too much of a pattern in when it occurs, but I only notice it in the first three gears, and more often when I'm decelerating. It doesn't seem to make a huge difference whether I'm braking, turning, or depressing the clutch; it just comes and goes seemingly at random. It started off very occasionally and almost unnoticeable, and has gotten louder and more frequent over the last several hundred miles.

I'm not a mechanic by any means, but also don't have money to throw at diagnostics. I subsequently inspected the cv boots, which do not appear particularly worn, and have no cracks or leaks; tested my bearings and got no play in the tire; and looked for unusual wear on the tire and came up empty. I can't find anything rubbing against the wheel or anything else, nor can I find anything that looks different or out-of-place around that wheel as opposed to the others. The closest thing I have to a theory is that the caliper might be sticking, as the rotors and calipers are pretty badly rusted all the way around. But then I'd expect it to pull a little to the left when the sound started, as opposed to continuing to pull gently to the right like it has since I got it. (I assume it could also use an alignment.)

So I'm clearly confused. I guess there's also the chance it's coming from somewhere in the drive shaft, but it really appears to be coming from the back-left.

Does any of this ring a bell with anyone? Any speculation or advice? I can use all the help I can get, as I'm on a budget like you wouldn't believe, and I can't afford to wait for my vehicle to break down completely before I fix it.

Thanks again!

Comments

  • xwesxxwesx Fairbanks, AlaskaPosts: 8,571
    edited February 2013
    Since you mentioned the drive shaft, have you considered looking at the heat shields that wrap over the top of it? I once had a bent shield that would gently rub the driveshaft and cause a noise that varied. Interestingly, it was louder while accelerating, probably because of the slight torque placed on the shaft during acceleration. The sound seemed like it was coming from the rear left of my car, when it was actually rear-center.

    Also possible is a wheel bearing, though it is odd that you wouldn't get any play when checking it, or the debris shield on the back side of the brake rotor.

    If a caliper is sticking, but not sticking tightly, you might not notice a pull to the left since it is on a rear wheel (or so you suspect). If it were a front wheel making the noise, you could definitely rule out a caliper due to a lack of pull.

    It's always a risk to get an older vehicle like this, but these are good cars and really do last if you take care of them. How are the struts on this one?
    2010 Subaru Forester, 2011 Ford Fiesta, 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup, 1974 Ford Pinto Wagon
  • ateixeiraateixeira Posts: 72,587
    It still sounds like a wheel bearing to me.

    Does the noise change its pitch with speed?

    Also, do your hear anything in neutral with the engine revving? My guess is no.

    Check the rear diff fluid level. Remove the top bolt and stick your finger in, see if the fluid is clean or smells burned.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,571
    Oh, goodness, yes! Check the rear differential. Actually, you should check and/or replace all the fluids just to set the clock to zero if nothing else. transmission, front differential, rear differential, and brake fluids are very frequently overlooked as part of normal maintenance. :sick:
    2010 Subaru Forester, 2011 Ford Fiesta, 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup, 1974 Ford Pinto Wagon
  • nsunbeamnsunbeam Posts: 2
    edited February 2013
    I've definitely got a couple loose and rusty heat shields, they make an interesting buzzing sound from the drive shaft when I rev the engine. An honest transmission specialist confirmed for me that it's nothing integral. I don't think that the aforementioned sound is related to this, as I don't hear it (only the buzzing) when I'm revving the engine out of gear.

    As for the struts, they appear to be in alright shape, but my judgement is a little skewed because my last several vehicles have been very old (20-40 years old) and without particularly effective shock systems. I'm not sure how to physically inspect the struts (something I'll be looking into) but I haven't really noticed it clunking or bouncing over bumps. Given how little I paid for it, I'm altogether impressed with the handling.

    The initial diagnosis that popped into my semi-educated mind when I first heard the sound was the bearing, for sure. Comparing the physics to the nature of the sound, that makes an undeniable amount of sense. But I also know that failed or failing wheel bearings will make a louder sound at higher speeds, whereas this is non-existant or indistinguishable at higher speeds, and tends to get louder as the vehicle is slowing down. I convinced a tire shop to put my car up on the lift for free to double-check my test, and they also got no play in the wheel. I'm under the impression that there are more bearings in the cv boots; could one of those potentially fail without the cv joint also failing? I also know that there are bearings in the differentials and transmission as well; not sure if one of those on its way out would make a similar sound.

    In the mean time, I'm going to go check the fluid in the rear differential. I'd already checked the transmission and brake fluids, which both look as though they were changed recently by the mechanic I purchased the car from. It hadn't occurred to me that the differentials took fluid separate of the transmission (I'm showing my ignorance again!) so thank you so much for the tip. If it looks clean and at the proper level, I'll probably return for now to the rusty-brakes theory.

    Thanks again for the feedback. Despite her developing quirks I'm really sold on the Subaru Outback, and I'm more than willing to take the time to fix her up, as long as I can figure out where to start! Those heated seats have got to be worth it. =D
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,571
    I had a 1996 Outback with the 2.5L (DOHC) engine, and I really enjoyed it. I had 220,000 miles on it when it crashed, but I'm sure there would otherwise have been many more added to the odometer.

    Good luck with it!
    2010 Subaru Forester, 2011 Ford Fiesta, 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup, 1974 Ford Pinto Wagon
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