Kubota brakes locking up

[reddog60]

Hi, I recently purchased a second hand Kubota M6950DT, unknown "real" hours or service history. It runs good but will randomly lock up the brakes when driving along (even if they haven't been used for 10 ~ 30 minutes previously) typically when driving between paddocks in a straight line as opposed to trying anything fancy such as stacking hay in a confined area. At all times the hand brake lever is off.

When it happens the tractor slows down and clearly starts to labour and will eventually stall. If I'm on a road my only option is to try to get off ASAP while I try to sort the issue. Operations such as trying to reverse up, change gears, switch from Hi to Low range etc has little effect and the brakes just appear to lock up harder. I've found turning off the motor and letting the machine stand for a couple of minutes will generally release the brakes although sometimes after restarting I have to select reverse to ensure the bakes have "unlocked".

Any suggestions as to what's going on?? and what I should do (other than sell it) - Thanks Paul

 

[Rosher18]

With unknown service history, have you checked the hydraulics for water contamination? This is a stretch but maybe the water is heating up and binding the wet brakes up?
I see on tractor data this has hydraulic wet brakes. Maybe heat is building from friction and causing water contamination in the brake fluid(?) to turn to steam, pressing the brakes closed and locking the wheels up.

 

[RjCorazza]

That is a curious failure. My first thought would be to check the linkage, although I'm not sure how that would activate the brakes while in use.

 

[kestrelrogers]

I’ve never run into that exact issue on an M6950DT, but it sounds like the wet brake discs might be swelling from contaminated or incorrect hydraulic fluid. I'd start with a full fluid flush and check for moisture or the wrong oil type. Hope it's something that simple and not internal brake binding!

 

[reddog60]

Hi Guys,

Thanks for your thoughts, I'll have a look as soon as possible. I have to say I agree with RjCorazza it's pretty weird as it's most likely to happen while driving along a straight road and it's been a minute of more since the brakes were last touched.

 

[mikester]

You will need to open things up and have a look. I had a similar issue on my Case 580D. When I opened it up I found that the brake shoe had fractured and a loose piece was getting jammed between the drum and remaining show. Removing the broken piece solved the toggle switch brake problem.