B7500 HSD bogging down & overheating

[enonhall]

I have read the previous posts on overheating, but I am not sure my symptoms match those exactly.

I have a 1-1/2 year old Kubota B7500 HSD. In the past month it has started overheating almost immediately when mowing.

I can run it all day without the PTO engaged...no problem.
I can run it all day with the PTO engaged and the mower deck off the ground...no problem (not that I do this).
The minute I start cutting grass (even short, thick grass) the engine bogs down, black smoke emits from the engine and the temp gauge shoots almost immediately to the red.

The coolant will boil and overflow. Once left to sit, the engine cools pretty quickly. But when I restart...it all starts all over again.

I replaced the mower deck blades (they were in bad shape) and the belt (which had actually came off) two weekends ago. Didn't help. I can only assume that I got the new belt on tight enough. I asked for a tension gauge (which the manual says to use) when I bought the belt and the guy behind the counter said "nobody uses those...just make sure it's tight, but not 'banjo string tight.'" I think it falls somewhere in that range of tightness.

I keep the radiator screen clean, but I have not yet blown out the radiator itself with compressed air. Will try that this weekend. I had also planned to pick up a thermostat Sat am too, just in case that could be the problem.

Any help that anybody can provide me would be greatly appreciated! My grass is getting knee deep while I try to solve this one weekend at a time.

Thanks!
Bill

 

[slowzuki]

There is something wrong with your cooling system, don't keep overheating it, it will damage the engine!

I suggest cleaning the radiator screen, it could be plugged solid, check the fan, the viscous clutch (if it has one) may be shot. When it is cool make sure it has the correct coolant amount and mix in it.

The PTO load causes the engine to develop more power which your cooling system can't keep up with.

Ken

 

[Bob_Skurka]

I wonder if there is something wrong with the PTO itself? If the engine bogs down & overheats when you engage the PTO, my suspicion is that there is something broke INSIDE the tractor and it is creating undue strain on the engine which creates the excess heat due to the engine bogging down. That is my guess. Then again, I sell candy to kids, so I never claimed to be too smart!

 

[Henro]

<font color="blue">
I have a 1-1/2 year old Kubota B7500 HSD. </font>

Warranty is 2 years everything, 3 years powertrain, isn't it?

Why not let the dealer fix it? Worst it should cost is the pick up and delivery...

 

[enonhall]

It doesn't really bog down when the PTO is simply engaged, but it does when a load is put on the PTO...cutting grass.

And I'm not running it while overheating, Ken. It starts overheating...I stop fast.

 

[enonhall]

Getting it hauled away to the dealer is definitely an option I will exercise if I need to. I just wanted to make sure that I wasn't overlooking something silly on my end. Would be painful to be without it for a couple weeks. (Not that it's doing me any good right now! /forums/images/graemlins/tongue.gif )

Is it possible that the mower belt isn't tight enough and that's putting strain on the PTO/engine? It sure seems tight...

 

[Bob_Skurka]

I think this is a warrenty issue.

 

[enonhall]

It would not overheat with the mower engaged sitting in the driveway. I have tested this with the mower deck up in the air out of the grass.

 

[Bob_Skurka]

Sounds like something is causing the a serious binding issue? But why would the blades free spin with the deck up and then bog down so badly when they engage a little grass? Like I said, I sell candy to kids . . . I don't have to be too smart to do that for a living.

 

[Henro]

In that case it could be something as simple as a stuck thermastat...even then...on a new tractor you might want the dealer to fix it cause you paid for the warranty in the purchase price...

Sounds like as soon as you ask the engine to do a little work it overheats. But it will run forever at reasonable temps when it is not working, right?

If something keeps the coolant from circulating, the engine will soon overheat because the coolant can't get to the radiator fast enough to expel the heat.

It is probably a simple enough thing to check yourself. But you need to be careful...it would be unfortunate if you voided your warranty (don't know if a tractor is the same as a laptop or not) because you did something on your own...