Loud whistling sound when firing up new MX4900

[njohnston77]

Hello,

I bought a new MX4900 HST in May 2025 and have less than 14 hours on it. Back in October I noticed every time I start it there is a very loud high pitched whining or whistling sound that stays for at least 10-15 minutes until the tractor warms up. This started when the unit had about 10 hours on it. I have noticed if I accelerate or reverse even just a little, the sound stops meaning it only makes the noise when idling.

I'm wondering if this is common for the unit when it gets very cold out? We are in Missouri so the past couple months have been pretty cold however I am skeptical because I am fairly sure I started noticing this sound prior to the weather getting below freezing temps.

Am I able to post a video on this thread?

Any thoughts are much appreciated.

Thank you!

Nick J

 

[North Idaho Wolfman]

Am I able to post a video on this thread?

Have you had the Dealer look at it, you do have a warranty for a reason.

Post the video on Youtube and then give us the link to see/hear it.

 

[njohnston77]

I do not have a trailer yet so I have no way of getting it to the dealer currently. I spoke with them on the phone and they mentioned it possibly being the turbo and to wait until spring time when it warms up to see if it goes away. I will work on uploading a video. Thanks

 

[njohnston77]

MX4900 HST high pitched whining sound

MX4900 HST high pitched whistling / hissing sound on start. Less than 14 hours on the machine and for the first 10 hours it never made this sound.

youtube.com

 

[JimmyJazz]

I certainly hear it and find it annoying. I don't know if it represents an issue that needs resolving. I always wear hearing protection when operating my tractor and other manly combustion powered devices and could possibly learn to live with it. Good luck. Always wear hearing protection.

 

[GrumpyFarmer]

Good day.

I am not a Kubota mechanic…nam a weekend warrior and pretend to be a farmer when I am not working for the man…so take this with grain of salt…

It’s really hard for me to tell but what I heard doesn’t sound similar to the HST whine of my Mx or my B. To me my B whines way more than the MX…I don’t even drive it without some cheese.

IMO what I heard doesn’t sound in yours sounds more like a rattle/high pitched clink of a linkage just vibrating (do you have a bucket level indicator rod or something else that is sloppy?). . I don’t know that to be true as I think it’s hard to tell the video.

what I heard in your video would not make me pump the brakes. But as I said it’s hard for me to tell.

im with @JimmyJazz on hearing protection and honestly when I forget mine, both my machines sound very unsettling compared to when I have protection. (As soon as I put ear plugs in I find my chi).

If really worried get it to a dealer to check. jMHO.

 

[McMXi]

I bought a new MX4900 HST in May 2025 and have less than 14 hours on it. Back in October I noticed every time I start it there is a very loud high pitched whining or whistling sound that stays for at least 10-15 minutes until the tractor warms up. This started when the unit had about 10 hours on it. I have noticed if I accelerate or reverse even just a little, the sound stops meaning it only makes the noise when idling.

I can hear the sound and it's kind of metallic and could be something vibrating at the right (specific) frequency. You mentioned that it goes away off idle or if you accelerate or go in reverse which would change the input frequency. I've noticed that the bucket indicator rod on my MX can vibrate and make a metallic rattling sound, but there are lots of components that could vibrate.

With the tractor parked, vary the rpm and see if the noise goes away and only returns at a specific rpm. A bad turbo would make a noise at all rpm values. It could be a bad turbo bearing I suppose, but you'd expect the noise to get worse as the rpm increases.

 

[njohnston77]

I can hear the sound and it's kind of metallic and could be something vibrating at the right (specific) frequency. You mentioned that it goes away off idle or if you accelerate or go in reverse which would change the input frequency. I've noticed that the bucket indicator rod on my MX can vibrate and make a metallic rattling sound, but there are lots of components that could vibrate.

With the tractor parked, vary the rpm and see if the noise goes away and only returns at a specific rpm. A bad turbo would make a noise at all rpm values. It could be a bad turbo bearing I suppose, but you'd expect the noise to get worse as the rpm increases.

I can hear the sound and it's kind of metallic and could be something vibrating at the right (specific) frequency. You mentioned that it goes away off idle or if you accelerate or go in reverse which would change the input frequency. I've noticed that the bucket indicator rod on my MX can vibrate and make a metallic rattling sound, but there are lots of components that could vibrate.

With the tractor parked, vary the rpm and see if the noise goes away and only returns at a specific rpm. A bad turbo would make a noise at all rpm values. It could be a bad turbo bearing I suppose, but you'd expect the noise to get worse as the rpm increases.

I just tried increasing the rpm with the machine parked and still heard that noise and it did get a bit more high pitched. As soon as I move forward or backwards it stops.

 

[Hugo Habicht]

I just tried increasing the rpm with the machine parked and still heard that noise and it did get a bit more high pitched. As soon as I move forward or backwards it stops.

HST pump so.

With my extremely limited knowledge of the drive system I would say nothing to worry about. And you wrote already, once the oil is warm, the noise disappears.

 

[McMXi]

HST pump so.

The most likely candidates are the hydrostatic pump, the turbo or something vibrating, and the pump does seem to be the most likely at this stage. Cold weather does tend to increase the whine. Perhaps time and hours will tell.