Strange noise at highway speeds

[syncmax]

my 2015 cmax hybrid has developed a strange noise at highway speeds. As far as I can tell it resembles the revving engine sound you hear as the plane is descending or ascending. It feels like it is coming from the back and it is there both in EV and ICE modes. I am going take it to the dealer but wanted to post here to find out if anyone else experienced it.

Edited May 2, 2017 by syncmax

[ptjones]

Are you sure it's not the tires? We have a few thread on this issue. :headscratch:  Does it get quieter when you slow down? Also Maybe bearing.

 

Paul

[syncmax]

thanks. it could be tires - it only has 25K miles (can they wear out this fast)

[stevedebi]

How often did you rotate the tires?

[ptjones]

Noise doesn't mean tires are worn out, just they're not wearing evenly.  Your alignment might be off. :sad: 

 

Paul 

[syncmax]

they are replacing the rear right wheel bearing under warranty. But they also somehow sold us their pot hole package which includes a wheel alignment @ $189.

 

Not very impressed with this car (warranty repairs this soon)

Edited May 5, 2017 by syncmax

[ptjones]

they are replacing the rear right wheel bearing under warranty. But they also somehow sold us their pot hole package which includes a wheel alignment @ $189.

 

Not very impressed with this car (warranty repairs this soon)

That's bizarre,  I had rear wheel bearing go too with low miles, but it was covered under warranty so no big deal. :) I have 154k mi. on it now so I got my moneys worth. I'll see if it makes it to 300k mi. :)

 

Paul

[rjam]

Hi Is the battery full. If you have a full battery the engine will sound like its going to red line when in fact the generator is spinning and no fuel is being used.

[plus 3 golfer]

Hi Is the battery full. If you have a full battery the engine will sound like its going to red line when in fact the generator is spinning and no fuel is being used.

Your statement is very confusing.  For clarity, I monitor rpm of ICE, the generator, and the motor all the time with ForScan.  When ICE is off (rpm = 0), the motor and generator spin at the same rpm whether the battery is full or not in my 2013 and assume the same in all C-Maxs.  That's the way the planetary gear system works.  One does not hear the generator spin when the HVB is full especially if it sounds like ICE going to redline. ;)  

 

ICE will spin when coasting if the HVB is full just like ICE in a "normal" car will do. The purpose of spinning ICE is to provide normal engine braking because engine braking can no longer be done with the traction motor (via regenerative braking) since the HVB is full.  One would have to be going very fast to have the engine near red line. 

 

If you have grade assist on going down a hill, ICE will spin if speed begins to increase and cannot be controlled by regenerative braking (either max regeneration is reached or HVB is full).  ICE rpm will vary (increase / decrease or shut down) to help maintain speed.  This is where ICE rpm can increase significantly if the hill is steep and can be heard. I have never seen grade assist use the friction brake to maintain speed.  The driver assumes such responsibility.

 

Bottom line: I'm not sure what you are trying to say with repect to the sound the OP is hearing.  The only time ICE spins more than what one would expect and may approach redline is when grade assist is being used.  The HVB does not have to be full for ICE to increase rpm to assist in maintaining speed (not speeding up) when going down hill using grade assist.

Edited May 6, 2017 by Plus 3 Golfer

[joshg678]

On my last trip I had a long slow down downhill from about 80mph and around 40 it started spinning the ice, even after a complete stop it ran the ice for about 6 seconds before shutting down. This was with normal brake petal.

This was before I had my scan gauge so I don't know what the RPM was but the mpg showed the usual 60 while stopped with spinning ice

Edited May 6, 2017 by joshg678

[rjam]

Your statement is very confusing.  For clarity, I monitor rpm of ICE, the generator, and the motor all the time with ForScan.  When ICE is off (rpm = 0), the motor and generator spin at the same rpm whether the battery is full or not in my 2013 and assume the same in all C-Maxs.  That's the way the planetary gear system works.  One does not hear the generator spin when the HVB is full especially if it sounds like ICE going to redline. ;)  

 

ICE will spin when coasting if the HVB is full just like ICE in a "normal" car will do. The purpose of spinning ICE is to provide normal engine braking because engine braking can no longer be done with the traction motor (via regenerative braking) since the HVB is full.  One would have to be going very fast to have the engine near red line. 

 

If you have grade assist on going down a hill, ICE will spin if speed begins to increase and cannot be controlled by regenerative braking (either max regeneration is reached or HVB is full).  ICE rpm will vary (increase / decrease or shut down) to help maintain speed.  This is where ICE rpm can increase significantly if the hill is steep and can be heard. I have never seen grade assist use the friction brake to maintain speed.  The driver assumes such responsibility.

 

Bottom line: I'm not sure what you are trying to say with repect to the sound the OP is hearing.  The only time ICE spins more than what one would expect and may approach redline is when grade assist is being used.  The HVB does not have to be full for ICE to increase rpm to assist in maintaining speed (not speeding up) when going down hill using grade assist.

[rjam]

Your statement is very confusing.  For clarity, I monitor rpm of ICE, the generator, and the motor all the time with ForScan.  When ICE is off (rpm = 0), the motor and generator spin at the same rpm whether the battery is full or not in my 2013 and assume the same in all C-Maxs.  That's the way the planetary gear system works.  One does not hear the generator spin when the HVB is full especially if it sounds like ICE going to redline. ;)  

 

ICE will spin when coasting if the HVB is full just like ICE in a "normal" car will do. The purpose of spinning ICE is to provide normal engine braking because engine braking can no longer be done with the traction motor (via regenerative braking) since the HVB is full.  One would have to be going very fast to have the engine near red line. 

 

If you have grade assist on going down a hill, ICE will spin if speed begins to increase and cannot be controlled by regenerative braking (either max regeneration is reached or HVB is full).  ICE rpm will vary (increase / decrease or shut down) to help maintain speed.  This is where ICE rpm can increase significantly if the hill is steep and can be heard. I have never seen grade assist use the friction brake to maintain speed.  The driver assumes such responsibility.

 

Bottom line: I'm not sure what you are trying to say with repect to the sound the OP is hearing.  The only time ICE spins more than what one would expect and may approach redline is when grade assist is being used.  The HVB does not have to be full for ICE to increase rpm to assist in maintaining speed (not speeding up) when going down hill using grade assist.

[rjam]

My experience driving steep mountain passes on the interstste with cruise on at the exact time the battery shows a full charge there is a very loud noise similsar to an engine at very high rpm. My understnding is this is normal. It will happen every time comming down steep grade with or without grade assisit but always with cruisevset.

[plus 3 golfer]

My experience driving steep mountain passes on the interstste with cruise on at the exact time the battery shows a full charge there is a very loud noise similsar to an engine at very high rpm. My understnding is this is normal. It will happen every time comming down steep grade with or without grade assisit but always with cruisevset.

It is the engine and normal when the HVB is full. The point is it's not the generator but ICE spinning (normal engine braking) that is heard.

 

Look at this post and you can calculate the generator rpm based on the formulae using ICE rpm and vehicle speed.  Again, if it happen "every time" then the HVB is full and ICE must spin because there is no regenerative braking.  ICE rpm (the amount of engine braking) will be controlled by varying the generator speed. 

 

It will also happen if the HVB is not full with grade assist when speed has increased above the grade assist threshold level established when grade assist was set AND regenerative braking is maxed out since speed is increasing.  ICE is then used in addition to regenerative braking to attempt to maintain speed going down steep hills.

Edited May 9, 2017 by Plus 3 Golfer

[Blodg1]

my 2015 cmax hybrid has developed a strange noise at highway speeds. As far as I can tell it resembles the revving engine sound you hear as the plane is descending or ascending. It feels like it is coming from the back and it is there both in EV and ICE modes. I am going take it to the dealer but wanted to post here to find out if anyone else experienced it.

 

Do you have the auto park option?