Metallic squeaking noise when switching drive/regen

[erikpo]

Lately my beloved PHEV have given a metallic squeaking noise when switching between drive and regeneration. It sounds like it's coming from the rear wheels, but I can't be 100% sure. I'm sure it's related to the switch from drive to regen and back though, as it also sounds when changing the B-level (brake by the handles) and I can't hear anything when the battery is at top charge and regen is deactivated. Louder with windows open.

Workshop had no clue... But they were about to switch brake callipers and said it could be related to that (although I'm quite sure it's not - at least it didn't help).

Anyone? Car is 4.5 years old, ~82.000km.

 

[NightPHEVer]

I'd suggest that you drive it, and after you've heard the noise (whilst trying not to use the brakes too much as discs always do get hot when they are used a bit, although that's more likely to be the front discs as they do most of the stopping), then see how hot the rear discs are getting. This is best acheived by poking them with your finger, although on the other hand if the discs are f*****g hot - because the potentially sticking handbrake mechanism means the calipers are slightly applied all the time - then you will probably burn your finger.

Immediate pain and the smell of burning flesh indicates that the calipers are indeed applied when they shouldn't be, but if the discs are just a bit warm then the calipers are not applied all the time. The sort of temperature that indcates f*****g hot is so f*****g hot that it can be felt like a radiator from a few inches away before you actually touch it and burn yourself, the centre of the alloy wheel will also be unusually hot. Also often accompanied by the small of burning paint and clicking noises as everything cools down.

But if it's not the potentially dodgy caliper problem then I don't know what it might be.

 

[ThudnBlundr]

This is best acheived by poking them with your finger, although on the other hand if the discs are f*****g hot - because the potentially sticking handbrake mechanism means the calipers are slightly applied all the time - then you will probably burn your finger.

Been there - done that :lol:

 

[erikpo]

But if it's not the potentially dodgy caliper problem then I don't know what it might be.

As an exchange of calipers didn't fix the problem I've kind of put that issue to the side, but this is a real simple test so I'll give it a try (I had absolutely no braking force on the right wheel with the handbrake on, and with the car lifted to swap tires I was still able to turn the left wheel by the bolt wrench with hand brake on...)

 

[NightPHEVer]

Oh, I clearly didn't get that they'd actually changed the calipers. So it's most likely not going to be the calipers (although I suppose it's possible if the handbrake cables are not adjusted correctly, but unlikely) as the sticking handbrake problem is a fault of the handbrake mechanism within the caliper itself, which as they've been replaced with what is with any luck the new, modified calipers (see '2015 PHEV Handbrake & Motor Lock Failure' on Techncal Discussions) they won't stick in the future. Although even if they were the original, dodgy caliper design the mechanism wouldn't stick that quickly.

 

[Tipper]

It might be worth looking at the rear motor unit and rear suspension mountings/bolts for tightness as it could be the torque reaction when you change the regen level moving something.

(Although having said that I would expect the dealer to have checked all that!)

 

[NightPHEVer]

It would be interesting to know exactly what occurs mechanically when the regen modes are selected. The front and rear electric motors somehow become generators. So it does seem likely that the noise has something to do with that process. Perhaps somebody with a better understanding than me could explain this function in simple terms.

 

[ThudnBlundr]

Basically a motor and a generator are the same thing. You put current in and you get torque out: you put torque in and you get current out. Of course it's not that simple in practice...

 

[erikpo]

It might be worth looking at the rear motor unit and rear suspension mountings/bolts for tightness as it could be the torque reaction when you change the regen level moving something.

(Although having said that I would expect the dealer to have checked all that!)

Rear motor fixing bolt would make sense to look at - on the rear the engine is used also as the generator, and if torque makes the engine move a little it would certainly make a noise.

Rear suspension itself is not likely, I can do any wiggling, jumping on the caravan hook, driving on bumpy road etc without this sound (as long as I don't touch the pedals).

I suspect the workshop did very little as they hoped the sound would disappear when they changed the callipers. After this work the battery was out and the petrol engine and full charge makes it a little hard to hear.

 

[erikpo]

Basically a motor and a generator are the same thing. You put current in and you get torque out: you put torque in and you get current out. Of course it's not that simple in practice...

Good point, but yes and no On the front the engine and generator are separate units, while on the back it seems the same unit does both jobs. https://www.mitsubishi-motors.com/en/showroom/phev/system/

This leads to the other comment about the fixing of the rear motor/generator.

 

[jaapv]

The same on the front - the electric motor is used for regenerating. The main generator is driven by the ICE.

 

[ThudnBlundr]

Basically a motor and a generator are the same thing. You put current in and you get torque out: you put torque in and you get current out. Of course it's not that simple in practice...

Good point, but yes and no On the front the engine and generator are separate units, while on the back it seems the same unit does both jobs. https://www.mitsubishi-motors.com/en/showroom/phev/system/

The generator at the front of the car in that graphic is the one used by the ICE when it's charging the car, which has to be independent of the motor as it can be used at any road speed. I think that both motors are used for regeneration

 

[mullet]

Lately my beloved PHEV have given a metallic squeaking noise when switching between drive and regeneration. It sounds like it's coming from the rear wheels, but I can't be 100% sure. I'm sure it's related to the switch from drive to regen and back though, as it also sounds when changing the B-level (brake by the handles) and I can't hear anything when the battery is at top charge and regen is deactivated. Louder with windows open.

Workshop had no clue... But they were about to switch brake callipers and said it could be related to that (although I'm quite sure it's not - at least it didn't help).

Anyone? Car is 4.5 years old, ~82.000km.

Hi all,

I know this is an old thread but found this by searching as my 2014 / ~230 000km PHEV is doing exactly the same thing. The sound seems to be coming from the front in my case. It is a high metallic squeak that sounds when applying the gas and brake pedals appropriately.

As the OP discussed, my logic also says it could have something to do with the car switching from and to the regeneration. I have to say I have heard this sound for a year or two but lately, it seems to come a bit louder. Nothing major though, a bit hard to hear with the windows shut but from the outside of the car, it is quite distinct.

@erikpo - did you ever come to any conclusion or found a fix for the issue?

 

[greendwarf]

I'd say its the brake callipers sticking (a known problem on PHEV). When you momentarily remove or apply load to a spinning disc (e.g. circular saw blade, bicycle wheel, computer discs etc. I've noticed a tendency to produce sounds by touching nearby close objects. I've put this down to a small distortion due to the mechanical stress changes in the material spinning. :?:

 

[richi]

A common problem that can cause this is one of the rear motor mounts (sometimes called "diff mounts" by Mitsubishi techs). It's the frontmost of the three that normally dies, by splitting its rubber insert.

The official replacement part has been redesigned. Or pattern parts are available.