[RidingWV]

Greetings. Our 2019 Forester (base) has a problem that has become more noticeable and irritating lately. It may be because of the colder temps or just coincidence.

For the first 8-10 miles, I get a very low frequency rumble between 20-40 MPH that is very noticeable especially when I take my foot off the gas and "coast". It sounds like low thunder in the far distance, but is constant and is actually louder than the tire noise. Almost sub-sonic frequency. Touching the brakes makes no difference, so I think I can rule that out. On one section of local road, the pavement has slight ripples, and the noise fluctuates with that, making me think suspension, bearings, or perhaps half-shafts.

After driving 8-10 miles, the noise is not nearly as noticeable.

The car only has 19K miles, and has been driven very conservatively. No wrecks, no off-roading, no tracks days. Lol.

I'm planning to take it in to the dealer, but would like to have at least a short list of possibilities to offer. By the time I drive as far as the dealership, it has "warmed up" and is not making the sound.

(PS - I tried searching for this and had no luck. If I missed something, please point me in the right direction.) Thanks!

EDIT: I forgot to mention I do have the tires right at 32/33 psi as shown on the door-frame decal, so they are not over-inflated.

 

[bman400]

What has the dealer said? It's still under warranty? Sounds like bearing.

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[FixinSube]

Put it in neutral and coast to see if the rumble stops. If not, rev the engine while in neutral to see if the rumble changes with rpm. That might help narrow down where the sound is coming from

 

[RidingWV]

What has the dealer said? It's still under warranty? Sounds like bearing.

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I've not taken it to the dealer yet. I was just hoping to maybe hear from someone who is aware of what the problem is so I could offer that idea to the service rep.

Yes - still under warranty. I bought it new in Oct 2018 but I also have the Gold 7yr/100K warranty with zero deductible.

It's just very annoying.

 

[FelineFreddie]

Bad bearings generally don’t change sound even after they warm up from being cold, but tires can be temperature-sensitive. In particular, wheel bearings don’t change “tone” from being under load to not being under load (as in shifting from drive to neutral and having the noise disappear. Gears, on the other hand, may change noise level from load to no-load situations.

Its also possible that it’s a drive-train component (transmission, transfer case, etc.) could be the culprit, with the sound produced being reduced as the lubricant temperature rises.

Without being able to actually road-test the vehicle, it’s practically impossible to do anything but guess.

If it only happens when the vehicle is cold, you might leave it a the service department overnight so the tech can do a test drive/sound check in the morning when the vehicle is cold. That’s probably your best bet in resolving the issue.

 

[Kevin]

wheel bearings don’t change “tone” from being under load to not being under load (as in shifting from drive to neutral and having the noise disappear

True. But a way to check for bearing noise is to find some S bends and traveling at a reasonable pace to load the bearings you will be able to tell if you have a bearing problem.

 

[Mrfox]

A lateral load (turn) on the bearing will make it change the sound it’s making (louder), it’s the easiest way to diagnose one (while driving at least).

My armchair QB guess? Your tires, they are typically louder when cold (stiffer) and sound would fluctuate over uneven surfaces. Tires often make noise at a particular speed range. As they wear the sound they make changes because what may have once been deep grooves or sipes is now a more solid surface. Compounds on some tires are intentionally different on outside.

Sorry, to the point finally- entirely possible they are making a different noise in cold weather with 19k on them vs when new and warm (and sound goes away once tires are warmed up). Simply curious what tires are they?

 

[UhOh]

I'm planning to take it in to the dealer, but would like to have at least a short list of possibilities to offer. By the time I drive as far as the dealership, it has "warmed up" and is not making the sound.

You will need to leave it at the dealership overnight so the mechanic can drive and experience the issue; otherwise don't even take it in. Nobody can fix what they can't identify.

 

[RidingWV]

@Mrfox,

Thanks. Last October, they replaced the OEM Ecopia tires at 18K miles due to early and uneven treadwear. I chose General Altimax RT43 tires, as I have had those on several cars over the past 10-15 years. Up to now, they were all quiet, and even on my other cars they never made this noise. I will keep that in mind, though. Thanks.

 

[Stonegroove]

I have two 2017 and I notice the same thing in both vehicles at the speed you mention. I believe it is caused by the CVT moving to a higher ratio early to save MPG and the engine is slightly lugging. If I ease or increase throttle it goes away. I think is just the design. Once past that 20-40 mph its fine.

 

[Mrfox]

Up to now, they were all quiet, and even on my other cars they never made this noise.

Well there goes my theory, mysterious noise 1, me 0

Diagnosing on a forum makes me appreciate how Tom and Ray Magliozzi must have felt during "Stump the Chumps", although they had the benefit of being much smarter than I am.

I think Stonegroove's explanation makes sense, perhaps it fades as the engine warms and runs smoother (happier at low rpms)?

Good luck I hope you figure it out, let us know what it is when you do.

 

[RidingWV]

I'm not ruling out the tires. Thanks for your suggestion.

 

[Stonegroove]

You can see if its tires by either letting off the accelerator or giving enough pedal (like passing) during this 20-40 mph speed for the cvt to downshift. In mine its more of a low vibration like a manual transmission that is in too high of a gear for the speed I am going.

 

[TedL5]

I'm not sure you would want to go in with a list of possible items for the tech to check. A wise service writer would take down your list of possible diagnoses and file it. Saying "It's a rumble just like I heard 5 years ago when I needed a wheel bearing" is descriptive of the symptom. And quite different from "I went on the internet and got a bunch of suggestions from people and here's the top ten suggestions for you to check." Which some techs might take as an insult to their competence. But it's your car, your $, my advice is likely worth the price I'm charging.

 

[PeterfromOz]

Tyre tread patterns can give various noises. Check the trad has not turned into a shark tooth shape caused by hard braking.

Several years ago I had vehicle with two different brands of tyres. Eveyone including me thought it was rear wheel bearings. I changed the rear wheel bearings but the noise was still there. I then swapped the rear tyres to the front and the front then gave a wheel bearing type rumble. Got rid of those tyres and the noises went away with the tyres.

 

[RidingWV]

@PeterfromOz Thanks. The tires should be like-new since they are only 1,000 miles old. They were replaced in October, but it hasn't been cold here until the past week. I've had the RT43 tires on several vehicles in the past, and have never heard this. Maybe the design of the car (harmonic frequency) brings out the noise. We'll see.

@TedL5 Yes, I agree. I would certainly do it in a non-condescending, diplomatic manner. Our Subaru dealer service writers have been very good since the new owner took over last year. In fact, they are the ones that offered to replace the OEM tires for free (plus free alignment) when they were wearing unevenly and early at only 18K miles. We have a good relationship.

 

[Vishnu]

True. But a way to check for bearing noise is to find some S bends and traveling at a reasonable pace to load the bearings you will be able to tell if you have a bearing problem.

My experience has bad rear hub bearings make a noise very similar to the sound of a twin engine airplane with the engines out of sync, meaning a drowning sound. Best of luck.