Rhythmic vroom-vroom noise coming from underside of car

[clonzana]

Toyota Yaris Hybrid 2017

Lately, I’ve noticed that when travelling above 40mph, I notice a vibrating engine-like noise coming from underneath the car which is a low pitched vroom-vroom-vroom noise, at intervals of about a second or so. Travelling at higher or lower speeds doesn’t seem to change the frequency, and it’s not really noticeable at speeds below 40mph. 
 

it’s very low pitched, like a dull vibrating sound and not very loud, but regular. Tyre pressures all fine, one tyre is slightly more worn than the others but not by much. 
 

wondered if this is normal / other Yaris Hybrid owners have this same thing. I’m not sure if it’s a new thing or it’s just something I’ve recently noticed and thus talked myself into it being a problem. 
 

thanks

[Max_Headroom]

Could you post a video so we can hear the sound?

[Gerg]

A bit of a wild guess here - are the plastic undertrays properly secured i.e. they have all their clips in place?

If these are ever removed by technicians, it's a popular time-saver to not put all the clips back. 

Which can could a plastic panel under panel to resonate in the fast-moving breeze, perhaps.

[TonyHSD]

Hi, 

Toyota hybrids tend to produce a very similar noises as you had experience. These noises only present at certain speeds and load of the hybrid system and sounds very much like passenger aircraft preparing to land and reducing its engine thrust., ( exactly these vroom vroom noise) 👍

They can come at speeds close to 60mph on flat roads when engine is only ticking over, similar to when at around 40mph.
Newer models might not have those present or might show at higher speeds because of their ability to remain in ev mode at higher vehicle speeds.. 
The noises comes from differences in rotational speeds of the engine camshaft , MG1 and MG2 all combined together in the planetary gear set ( power split device). 
On gen 3 hybrids when EGR system it’s fully or partially blocked these noises can be more pronounced and more vibrations felt through the cabin. 
If we are taking about same vroom vroom sounds then these are typical and nothing to worry about it. If the car has some mileage on 100k + miles egr system check and clean can be performed as preventative maintenance. 

[clonzana]

Thanks all for your responses. 
 

video: not really able to pick it up as it’s more of a feeling / vibration than a noise, sorry. 

plastic trays: not able to get underneath the car, but thanks for the suggestion. I’ll bear it in mind. 
 

I’ve just noticed that the sound seems to be exacerbated when I’m going around a roundabout (U.K.) in which the faster I go around it, the more low pitched continuous rumbling sound I hear. This sound alleviates as soon as I turn off the roundabout ie the centre of mass shifts towards the left side of the car. 
 

the tyre which appears to be more worn is the front driver tyre, but as I said, it’s not hugely more worn than the other tyres. 
 

I’ve seen videos of issues with wheel bearings which don’t sound like the issue I’m having. 
 

thanks again 

[TonyHSD]

4 hours ago, clonzana said:

Thanks all for your responses. 
 

video: not really able to pick it up as it’s more of a feeling / vibration than a noise, sorry. 

plastic trays: not able to get underneath the car, but thanks for the suggestion. I’ll bear it in mind. 
 

I’ve just noticed that the sound seems to be exacerbated when I’m going around a roundabout (U.K.) in which the faster I go around it, the more low pitched continuous rumbling sound I hear. This sound alleviates as soon as I turn off the roundabout ie the centre of mass shifts towards the left side of the car. 
 

the tyre which appears to be more worn is the front driver tyre, but as I said, it’s not hugely more worn than the other tyres. 
 

I’ve seen videos of issues with wheel bearings which don’t sound like the issue I’m having. 
 

thanks again 

Well in that case you need to check wheel bearings and particularly front left one. Tyres too for proper inflation and tyre west. 

[bathtub tom]

2 hours ago, TonyHSD said:

Well in that case you need to check wheel bearings and particularly front left one.

+1

[clonzana]

Thanks. Upon further inspection, I have noticed that both front fender liners appear to be damaged in that they are missing a roughly V shaped piece on both sides. 
 

could this contribute to the sound? Although I’m not sure why it would be worsened when turning. 

[anchorman]

5 hours ago, clonzana said:

Thanks. Upon further inspection, I have noticed that both front fender liners appear to be damaged in that they are missing a roughly V shaped piece on both sides. 
 

could this contribute to the sound? Although I’m not sure why it would be worsened when turning. 

Wheel bearings make more noise as the weight transfers onto them.  If you aren’t sure enough to diagnose it yourself, take it to a garage.