2012 CT225 Noisy HST

   / 2012 CT225 Noisy HST #1  


New member
May 7, 2022
Bobcat CT 225
I recently purchased a 2012 ct225. It's in great shape over all and has 650 hours on it. However, the hst sounds terrible. To me it sounds like there is air in the hydraulic pump, or a grinding noise. After I brought the tractor home and read through the manual I realized the previous owner had the vent on the hydraulic fill cap upside down (the gooseneck on the fill tube), would this have been a cause for my grinding noise? This is my first tractor and hst powered piece of equipment so I am unfamiliar with hst's. I have new bobcat fluid, but I'm still trying to find aftermarket filters if I can. Does anyone have any part numbers or does Kioti match up with the same transmission? If the tractor is at low rpm it doesn't sound too bad, but after some heavy use or higher rpm you can sure notice the grinding. Could this just be hst whine for this tractor, the motor sure is noisy so maybe its just the way it goes?

   / 2012 CT225 Noisy HST #2  
Just a quick comment regarding the filter - if it were me, I'd use oem filters for oil/fuel/hydro oil - there can be minor differences with after market filters. I think it's worth the little bit of extra money.

just my personal opinion of course.......
   / 2012 CT225 Noisy HST #3  
I’ve only got 200+ hours on my 2012. The hydro does make a fair amount of noise. Could be my fault, as I let the fluid level get low last year. I almost always have on hearing protection, so I don’t notice it very often. Still runs like new..
   / 2012 CT225 Noisy HST #4  
Can’t say that I ever noticed any grinding noise. Is it only when the tractor is moving or is it constant when it’s running. And I’m not sure about the vent I wouldn’t think that would be an issue unless water got in there. How’s the fluid look?
   / 2012 CT225 Noisy HST #5  
Most HST tractors I've run are obnoxiously loud to the point where I won't run em without something in my ears. Its very likely that it just is what it is unfortunately. Still probably worth having someone listen to it that would know though.
   / 2012 CT225 Noisy HST
  • Thread Starter
It's a little late for a reply but I switched out the fluid and filters back in June. I found a big spiral shaving when I drained the oil. The tractor only makes bad noises when its driving, using the pto and a wood chipper did not seem to cause any issues. After some for research could it be an air leak on the suction side of the pump or possibly an issue with the drive system? I haven't seen any foaming of my oil but I have seen air bubbles while checking the oil level. I haven't thought if it as concerning as its never looked bad. I put another 50 hours on the tractor since then with impact to operation. Working in the cold had no affect either (-12 C) Do these tractors have screens on the suction side of the pump that need to be cleaned periodically, I know my neighbours Kubota does.
   / 2012 CT225 Noisy HST #7  
I believe all you have is screw on filters. No cleanable screens.
   / 2012 CT225 Noisy HST #8  
Late reply here also; as I don't have a bobcat, but my tym has a removable/cleanable screen inside the suction hose that attaches to the transmission -- perhaps Bobcat does also? You being an Bobcat owner would probably know if you do. IDK but it's a thought to check out. Good luck and best wishes.
   / 2012 CT225 Noisy HST #9  
Where does the noise you’re hearing sound like it’s coming from? Front,middle or back of the tractor. Mine makes a grinding- whining sound from the rear after fluids get hot.
   / 2012 CT225 Noisy HST
  • Thread Starter
So I finally got around to having a local HD mechanic come by who is experienced in compact tractors. He figures the noise and squealing is coming from the motor relief or hot oil bypass. I also cut open the HST and hydraulic filters. Both are clean. So good news all around. When the weather warms up i might attempt to check the pressures in the system and see if they need adjusting. All in all, its nothing to worry about. I will most likely continue to run the tractor as is without any tinkering.