Brake Fade on Tractor

[sstterry]

My main tractor is a 71hp 62hp pto that uses a "wet brake system". I have been using it the past couple of days to do some brush hogging. I have noticed that it is running hot and I assumed it was because I was pushing it pretty hard in some tall weeds. But yesterday I was pulling a 10ft brush hog up a pretty steep incline (welcome to east TN) and went to downshift and realized I had no brakes. As my grandfather used to say, my but* could have pinched a 20 penny nail.

It is topped off with anti-freeze and is full of brake fluid. The radiator and fins are also clean. Could a thermostat problem be causing the brake fluid to overheat?

 

[greybeard]

The wet brake systems I'm familiar with run in hyd oil. does it have an oil cooler?

 

[cowski]

it would help to know ,what kind of tractor u have?

 

[sstterry]

The wet brake systems I'm familiar with run in hyd oil. does it have an oil cooler?

I am not aware of one, but that does not mean that it doesn't. I had assumed that since the engine was running hot that that system would also cool the brake fluid. I have seen nothing in the owners manual about an oil cooler.
The tractor is an AGCO GT65A. I have never had this problem before.

I might add that the Manual is pretty specific about the Brake Fluid to be used. It has to be at least a Dexron III and not DOT fluids.

 

[Caustic Burno]

Is there a cooler in front of the radiator? If so that should be the transmission cooler.
Massey's have one not sure about all AGCO products.

 

[sstterry]

Is there a cooler in front of the radiator? If so that should be the transmission cooler.
Massey's have one not sure about all AGCO products.

I don't remember seeing one, the AGCO brand was mfg'd by SAME for sale in the US. I will look for a cooler tomorrow.

 

[greybeard]

The brake discs run in Dexron AF or is that just for the master cylinder that actuates the discs?
Most anti-freezes will destroy fiber discs.
When you say "no brakes" do you mean the pedal goes down as normal and is hard but won't affect the tractor's movement or does the pedal goes to the floor?
(I know nothing specific about an agco)

 

[sstterry]

Dexron III or above AT Fluid, not antifreeze. The manual is very specific on this. It says do not use any type of DOT fluid or it will damage the seals.

Since they are "wet brakes" I assume they run in the fluid and not just actuate the master cylinder.

The brake pedals go to the floor. When the tractor cools down, the brakes work fine. This is not from overuse of the brakes at all, they are rarely engaged except for shifting gears on a hill.

It is my understanding that with "wet brakes" if the fluid gets too hot, a gas develops that prevents the fluid from properly engaging the discs.

 

[Caustic Burno]

I don't know about the gas thing.
I do know I got rid of a Kioti tractor that I failed the IQ test when buying.
The tractor didn't have a transmission cooler and in this Texas heat caused me lots of problems in the hay field. The next model up had one.

 

[greybeard]

Dexron III or above AT Fluid, not antifreeze. The manual is very specific on this. It says do not use any type of DOT fluid or it will damage the seals.

Since they are "wet brakes" I assume they run in the fluid and not just actuate the master cylinder.

The brake pedals go to the floor. When the tractor cools down, the brakes work fine. This is not from overuse of the brakes at all, they are rarely engaged except for shifting gears on a hill.

It is my understanding that with "wet brakes" if the fluid gets too hot, a gas develops that prevents the fluid from properly engaging the discs.

Of course.
My mind went to Dexcool, instead of Dexron.
What does the manual say is the refill capacity for the Dexron? (trying to get my mind around something here)
Pedal to the floor is almost always a case of foam or air in the master cylinder. I have to think it would be foam since it only happens after a period of time when hot.
Does it improve any if you immediately pump the brake pedal?
I could certainly also be a case of a bad thermostat.

 

[Nesikep]

Wet brakes actually run IN oil
They are PROBABLY also actuated BY oil.

Did it feel like the brakes were dragging?

a soggy pedal would be gas (boiling) in the actuator side of it preventing any pressure from getting applied, a pedal that feels good just doesn't do much would point to the linings being overheated, and unless the brakes drag you'd never get them hot enough just operating the tractor

 

[sstterry]

Dexron III or above AT Fluid, not antifreeze. The manual is very specific on this. It says do not use any type of DOT fluid or it will damage the seals.

Since they are "wet brakes" I assume they run in the fluid and not just actuate the master cylinder.

The brake pedals go to the floor. When the tractor cools down, the brakes work fine. This is not from overuse of the brakes at all, they are rarely engaged except for shifting gears on a hill.

It is my understanding that with "wet brakes" if the fluid gets too hot, a gas develops that prevents the fluid from properly engaging the discs.

Pedal to the floor is almost always a case of foam or air in the master cylinder. I have to think it would be foam since it only happens after a period of time when hot.
Does it improve any if you immediately pump the brake pedal?
I could certainly also be a case of a bad thermostat.

I think you are right on all of the above accounts. Talking this through has just about convinced me that it is the thermostat.
And no it does not improve to pump them. When it cools they work normally.

 

[sstterry]

Wet brakes actually run IN oil
They are PROBABLY also actuated BY oil.

Did it feel like the brakes were dragging?

a soggy pedal would be gas (boiling) in the actuator side of it preventing any pressure from getting applied, a pedal that feels good just doesn't do much would point to the linings being overheated, and unless the brakes drag you'd never get them hot enough just operating the tractor

Soggy pedal only after it heats up over a couple of hours.

 

[Caustic Burno]

Wet brakes actually run IN oil
They are PROBABLY also actuated BY oil.

Did it feel like the brakes were dragging?

a soggy pedal would be gas (boiling) in the actuator side of it preventing any pressure from getting applied, a pedal that feels good just doesn't do much would point to the linings being overheated, and unless the brakes drag you'd never get them hot enough just operating the tractor

This pretty much describes my 02 Kioti that didn't stay long. Tough tractor just wasn't designed for a Texas hayfield.
The next model up had an A4-236 Perkins I paid the stupid tax for not getting that model.

 

[Nesikep]

the A4 236, isn't that what the MF255's had? That's a really nice engine

 

[Caustic Burno]

the A4 236, isn't that what the MF255's had? That's a really nice engine

255 through 275 had that engine.

 

[sstterry]

I just wanted to update this thread and say that I replaced the thermostat on the tractor yesterday morning (took a week to get parts). The tractor is still running hot and now I am worried it either has to be the water pump (but no leakage anywhere) or my worst nightmare, a blown head gasket)

Is there any test I can do to see if it is the head gasket?

(By the way Graybeard, there is no separate oil cooler on this model)