My leaf is thrumming

[clivech]

I have a worrying sound from my 2014 Leaf. When it hits about 56mph there is a thrumming sound from in front of me. It seems to be coming from the engine compartment. It gets louder (even if you don't go any faster) and you can feel the vibration through your feet and the steering wheel. It seems to be particularly loud if the motor is working harder, going up a hill for instance. The only thing I can compare it to is a washing machine when the load is unbalanced. It's very worrying, but once you slow down it goes away and there don't seem to be any effects afterwards. I have had the tyres checked for being out of round and the front end checked out. Nothing. Is it possible something in the motor itself is out of balance? Or has anyone else experienced anything similar? Thanks.

 

[LeftieBiker]

It's possible, but I'd get a second opinion on the tires. Next, have the CV joints checked. Last, there are issues with Leaf axle bolts, but they don't usually produce what you describe. Good luck.

 

[GerryAZ]

Check to make sure that the plastic aerodynamic/splash shields are not torn and are properly secured. I have seen those splash shields on other cars flopping and vibrating at highway speeds. If in doubt, you could completely remove the set of shields as a test. That would also allow careful inspection of other components such as motor mounts and CV joints.

 

[clivech]

Hi GerryAZ: Are the shields you're talking about the plastic ones under the motor? There is one that goes all the way from the front bumper to behind the motor, and there seem to be two smaller ones on each side that just go from the bumper to the wheel arch. I notice I'm missing a vertical, comb-like piece on the driver's side, just behind the bumper (there's one on the other side). The main central shield seems pretty well attached, although there is some movement in it. One of the side ones may be missing a plastic stud or two.

 

[clivech]

It's possible, but I'd get a second opinion on the tires. Next, have the CV joints checked. Last, there are issues with Leaf axle bolts, but they don't usually produce what you describe. Good luck.

Thanks, Leftie. I'll have them take a look. I also like GerryAZ's idea that it could be a vibrating shield. But the vibration really transmits through the body of the car.

 

[LeftieBiker]

If the shields are made of the same thick, heavy (but not especially strong) fiberboard as others I've encountered, then that is the most likely culprit.

 

[MikeinPA]

Don't rule out a wheel bearing. The Leaf is quiet enough that a rough bearing can be heard and felt. But perceived symptoms vary a lot.
https://www.mynissanleaf.com/viewtopic.php?t=32351I replaced a bad right front bearing and fixed my hum--but the bearing that came out was still smooth turning.

 

[goldbrick]

^ that was my thought too. From the sound of it (no pun intended) it sure seems like a bad tire/wheel, wheel bearing or axle/CV joint. You could switch the tires front/back as a quick test to see if the wheels are really OK too.

 

[GerryAZ]

If the splash shield(s) are not properly secured (or there are sections torn or missing), the air flow under the car can cause them to move and vibrate. There could be certain resonant speeds (wind speeds) that cause heavier thumping that would stop when slowing down. I thought that the front splash shield is one piece (except for the little combs or air dams in front of the wheels), but I need to check the service manual or parts manual to confirm.

 

[Nubo]

Since the problem only seems to occur under torque, rotating tires front-to-back could help reveal whether it's a tire issue.

 

[Toby]

Some years ago we had a "thrumming" noise from under the front of our car when at highway speed. We took it to a nearby dealer and the service manager put the car up so he could get under and examine the tires. What he found was broken steel cables poking out of two of the tires. The tires were de-laminating. We were warned not to drive the car anywhere. Obviously, we replaced the set.

 

[LeftieBiker]

I had a similar experience with my '86 Civic Si, except that the broken belts were invisible. I actually got two new axles under an extended warranty before they figured out that it was the tires. That taught me not to go 130MPH in a 110MPH car!

 

[clivech]

Thanks, everyone for the input on this. I noticed the other day that it changes frequency (the hum pulses, normally with about a 3 second cycle) while the engine speed remains constant. So I know it's not the motor. It also didn't vary with road speed, which seems to rule out a bearing/CV joint. There is at least one stud missing from the shield under the motor, so I'm guessing it's that, although the fact that it can be felt through the body of the car suggests it may be something more substantial. I'll try the tyre/tire swap and see what happens - although again, the fact that it varied independent of road and engine speed makes me skeptical. At any rate, I don't think it's about to come to a stop on the road. I think it's something I'll have to get used to or maybe get lucky with replacing the shield studs. Thanks again,

Clive

 

[Skippy]

Just for completeness, another possibility is the rear window is open and the fronts are closed. The Helmholtz Resonance is wicked on Leafs at 50mph.

 

[Bombastinator2]

Can you make the noise? It’s what Bill and Ray on cartalk always asked. I’m not sure it did any good but they enjoyed it.