I’ve got an aging 2006 Mazda 3 automatic with 120k miles. It’s gradually been getting noisier over the past several months. It’s got a list of other things that I’m going to fix soon so I’d like to know which problems I can possibly diagnose and fix myself, and which are beyond the shade-tree mechanic.
Noise #1 is an intermittent, rasping/whooshing sort of noise that happens when the car is accelerating. It’s particularly noticeable when accelerating up hill, perhaps because it’s in low gear, mid-RPM, presumably open throttle. Power and throttle response remains smooth, and I haven’t noticed anything else wrong except the noise.
Noise #2 is a low frequency rumbling that happens when shifting into reverse, and decreases a bit when letting off the brakes to creep backwards. It also occasionally happens when in drive while stopped at a light. The car has also had a sequence of other transmission problems recently. Last year it started shifting rough, transmission fluid was changed by a chain oil-change shop and shifting was improved for a while. Later the transmission control module died which meant a trip to the dealer to get that replaced. While there they fixed a leaking transmission cooler hose probably caused by the barely competent drone working at the oil change shop. Now the car is starting to have rough shifts again, particularly from 1st to 2nd before the engine warms up. I’ve checked the transmission fluid since the leak was fixed, the level is OK but the fluid seems awfully dark for being only ~10k miles old.
Meanwhile, it just failed the RI state safety inspection for worn front brakes and a worn front lower ball joint. I think the inspector was being unnecessarily picky on the brakes, but they are near enough to the end of their life that putting of their replacement won’t really save much money. So I’ll be replacing the rotors and pads myself as soon as I get the parts and the free time.
The worn lower ball joint seems plausible enough to me since other suspension components on that wheel have worn out in the last few years. Now I’m just trying to figure out whether I’m up to replacing the whole lower control arm myself…
Anyhow, while I’ve got the car up on jacks and my tools hauled over to my garage, what should I look out for with all the new noises the car makes?
On #2, I like the broken engine mount idea. The mounts in the Mazda 3 are notoriously terrible, and I replaced the passenger side mount ~3 years ago. I just had my wife shift it in and out of gear with the hood open, and indeed the motor pitches back and forth rather dramatically. That seems consistent with a broken lower-rear mount.
Conveniently enough, I would have to unbolt that mount anyhow to get enough clearance to replace the lower control arm.
If you replace the control arm, it’s important that the pivot bolts be tightened under the proper condition. The arm needs to be where it would sit at rest with the weight of the vehicle on it, as if it were down on the ground. With the arm installed and the pivot bolts loose enough that they can be freely turned, get the car to rest on a support under the wheel hub or wheel end of the control arm, then tighten the pivot bolts to spec. If those bolts are instead tightened with the control arm hanging down it can make the handling squirrelly.
I agree that motor mounts are high on the suspect list for noise #2.
It’s a long shot for noise #1, but check for any looseness of exhaust system heat shields.
The tranny should have synthetic fluid (e.g. Mercon V), which should not darken or smell burnt for years. That fluid is rather expensive, so a shop that tries to cut corners might have used something cheaper. Try to determine whether the right fluid was used when it was serviced. If it has the right fluid, you could try some Lubegard transmission fluid additive (be sure to get the right type).
Thanks for the tips. I’ll be sure to tighten the arm pivot in the correct position.
On further reading, I see that rough shifts are another symptom of bad mounts. I’d sure love it if that fixed everything.
Does anyone have advice on buying aftermarket mounts? The dealer price is almost 4x higher. On the one hand, I know that the original supplier will often sell the exact same part as aftermarket. Some even show pictures of a part with the same “FoMoCo” stamp as the original part (like this Febest mount). But that could be plain old trademark violation. On the other hand, some of the aftermarket parts have worrying numbers of bad reviews (like this DEA mount).
On the gripping hand, my wife needs the car to get to work, and our garage is 200 ft away from the basement where I store my tools… so it might be worth buying parts from the dealer so I can get everything done in one weekend.
I’ll give this one more bump for any additional advice before I start working on the car this weekend.
Brake pads, rotors, and the control arm are ordered and on the way. I’ve got time and sunlight on Friday morning to jack up the car and inspect the motor mounts more carefully. If they’re bad I’ll probably just get replacements from the dealer rather than ordering and waiting for cheaper parts. I’ll do the work this weekend. My wife has a backup ride on Monday and my sister can drive me around to pick up parts I discover I need when the Mazda is taken apart…
Then, when I go for re-inspection I’ll have the shop check the transmission fluid.
Quality aftermarket parts are fine. I personally do NOT use china made parts for anything.
As you have guessed, many manufactures of parts for auto manufacturers also sell the same parts from the same batch to distributors like NAPA as “aftermarket” parts.
I worked for a gasket making company that did this. We made gaskets for GM, Ford, & Chrysler. We also sold gasket kits to NAPA & Auto-quest. They were made up from the same gaskets that we sold to Ford Etc.
It is amazing what odd bumps, rattles & vibrations can be cured with new engine mounts! I hope that this does indeed solve most of your problems.
Turns out the right mount is completely shot. I guess that’s what I get for replacing it with a cheap part 30k miles ago… Couldn’t thoroughly inspect the left mount without removing a lot other things but the part I could see seemed ok.
I also took a video of the lower mount moving around while I shift it between D, R, and N and revved the engine a bit. Does this look like excessive movement? Unfortunately I can’t actually look at the rubber part of this mount until I take it out since it’s in a pocket in the crossmember.
And now I’m thinking that if one mount is broken and another is worn, I should replace the third mount since it’s probably had excessive loads.
That’s a reasonable approach. However, some mounts get less stress than the others and it might still be okay. Can you detect any movement in it, either putting in gear as above or prying with a good sized bar?
The left mount is under the battery, wiring harness, and several plates and brackets so I can’t easily look at it while the engine is running. I think I’m just going to replace it for good measure, since by this point there’s been a lot of miles with the other mounts worn or broken. Besides, the procedure for replacing any mount requires loosening and tightening the bolts on all mounts in a specific order, so I’ll already be halfway to replacing the left mount.
I replaced all the mounts. Right mount was definitely shot, and the engine was resting metal-on-metal in the mount bracket. The lower mount was also fairly cracked and worm. Left mount might have been OK, just had a few surface cracks on parts of the rubber that didn’t seem to be bearing much load, but I replaced it anyways. Most difficult part of changing all of them was having to remove the battery, ECM, air intake, and an awful lot of wiring harnesses to get the left mount out.
Replacing the lower control arm wasn’t too difficult either. Four bolts and a bit of smacking and prying to get the old one out and the new one in.
The brakes were the hardest part of the job. It took many hours of swearing, banging, banging and prying, banging prying and heating, etc. to get the old rusted on rotors off.
The icing on the cake was the “oh shit” moment I had after I put everything back together when the ECM decided not to trust my keys because I somehow tripped the security lockout. Waiting and re-seating all the wiring harnesses fixed that though.
Now it runs so quiet and smooth! All the noises are gone. There’s still a bit of shift hesitation when the engine is cold, but it’s not anywhere near as jerky when it does shift.