Kubota 5030 HST problem

[millstreaminn]

My brother brought me his 2005 Kubota 5030 HST to look at. This tractor/loader has 1250 hours on it and has not been taken care of. He makes silt sock for the gas companies and uses this tractor to load mulch into his sock maker. Dusty, dirty conditions.

Here's the problem. If you set the engine to 2000 rpm and take the tractor into a pile of mulch, the rpm's drop to 1200 and the tractor almost stalls. If you let off the hydro pedal, the rpm's come back up. The loader works fine, up, down pressure will lift the front of the tractor up with no engine lug. The only time the engine lugs is when the HST tranny is engaged more than 1/2 way.

So far I changed the fuel filter (very dirty) drained the fuel tank and changed the hydraulic filter (looked like new). I checked all the fluids in the tractor and they look fine and were at proper levels. I called my Kubota dealer and they said to change the hydraulic fluid. 15 gallons of Kubota fluid is $325.00. Kubota recommends changing this fluid every 400 hours and this tractor has 1,000 hours on the fluid. I'm not opposed to spending the money for the fluid, but I just can't see it causing the stall problems?

I am going to hook the tractor to my irrigation pump tonight so I can load the engine with the PTO. I really can't tell if the engine is lugging because of something wrong in the hydro or the hydro is fine and there is a problem in the engine.

So my question is this: Has anyone every fixed a hydro problem by changing the fluid?

Thanks-

 

[oldnslo]

The HST is supposed to work that way. The farther you press the go peddle the faster it wants the tractor to move similar to shifting a manual transmission tractor into a higher gear. Higher speed for the same load requires more power.

 

[millstreaminn]

I've run this and several other hydro tractors before. There is something wrong with this one. It shouldn't act like it is going to stall when the pedal is pressed over 1/2 way.

 

[sandyc]

I'm just guessing but it sounds like a relief valve isn't working somewhere in the system.

 

[redsox1]

How about cleaning the radiator and screens?

 

[millstreaminn]

Hi.

Thanks for the replies.

Redsox: The screens are clean and I washed the radiator fins out.

I took the loader off and have been driving the tractor up and down the road. I set the rpm's to 2,000, tranny is in high gear and I take off. With the pedal half way depressed, the tractor moves fine and the rpm's stay just under 2000. When you quickly and fully depress the hydro pedal, the rpm's drop to below 1,000 and the tractor will stall if you keep the pedal fully pressed. This is on level ground too.

I hooked the tractor up to my irrigation pump (the pump only requires 30 hp to run) and the engine didn't seem to hesitate when the pto was engaged and the throttle was run at speed.

So far I have changed EVERY filter on the tractor. The only thing I haven't done is change the hydro fluid. I have 15 gallons of it sitting in the shop but am hesitant to change it until I have a better idea of what the problem is.

Thanks-Scott

 

[Kanook]

Do you get a similar reduction in rpms running in low range as well when you hammer the pedal? If in the HST I would expect it to behave the same but less pronounced due to the lower gearing. Sure sounds like a sick HST....Here's a stupid question but I'll ask anyway (and no offence intended)..Are the tractors brakes locked on?. My B2650 will drive around all day with the brakes locked and I won't know the difference until I need more power...don't ask how I know.

 

[big bubba]

just to ask, you say you changed all filters...but you didn't mention the air filter in your OP. dusty conditions could have restricted flow...is there smoke when it stalls? good luck

 

[millstreaminn]

Do you get a similar reduction in rpms running in low range as well when you hammer the pedal? If in the HST I would expect it to behave the same but less pronounced due to the lower gearing. Sure sounds like a sick HST....Here's a stupid question but I'll ask anyway (and no offence intended)..Are the tractors brakes locked on?. My B2650 will drive around all day with the brakes locked and I won't know the difference until I need more power...don't ask how I know.

It does act up in "M" and "L", just not as bad as when the hydro is in "H". L or M won't stall the engine like being in H will.

No problem with the brakes being on comment. Been there, done that too!

 

[millstreaminn]

just to ask, you say you changed all filters...but you didn't mention the air filter in your OP. dusty conditions could have restricted flow...is there smoke when it stalls? good luck

Yep, both inner and outer filters. I'm beginning to think this is beyond what I am going to be capable of fixing. Looks like a trip to the dealer is in order...