7745 BRAKES

[sawyer]

Hi Folks.
Very nice forum, great search engine too !
I searched for a brake problem similar to mine, but came up dry, maybe I overlooked it ? If so, i apologize.

It's a 7745. The brakes. Adjusted, bled and working well with plenty of free travel before actuation. Now it gets weird. Pulling an orchard sprayer NOT using the brakes at all, after one (1/2 mile) pass through the orchard, the pedals are up tight with NO free travel and the housings are hot from the brakes dragging/binding causing the tractor to STOP when the clutch is pressed. "Cracking" the bleeder releases the bind but how in the world can they "Self actuate" when NEVER pressing the pedals ? ? ?
And that "Isolator/compensator" thingy ..... can you please explain it's function and operation ? ? ?

I can stomp the pedal many (20) times and watch the brake parts working perfectly, ride around the lot testing/using the brakes for several minutes or so and everything works fine so a stuck "Check" valve at the master cyl. doesn't seem to be the issue.
Baffled .... thanks for any guidance.
Respectfully,
Russ

 

[corundal]

Odd thing is I have an identical fault in a very old car. It may not be the same, but I am looking at the master cylinder as not letting pressure back.
On my 6745 I once adjusted the handbrake bands too tight and they would bind as the tractor heated.

 

[alan]

Check you have free play on the master cylinder push rods, as no play will give you the symptoms you describe!

 

[forterra9641]

Odd thing is I have an identical fault in a very old car. It may not be the same, but I am looking at the master cylinder as not letting pressure back.
On my 6745 I once adjusted the handbrake bands too tight and they would bind as the tractor heated.

since this is a 7745 the handbrake is no a band. he hand brake just acutates the main brakes wich is dry discs. i would also think it would be a master sylinder problem.

 

[ixer0]

Hi

If the m cyl pushrods are okay it is probably the brakes are adjusted too tightly. I have come across this problem a few times and re-adjusting has cured it. Forget what the book says. Jack up and adjust the 19mm nut until the wheel locks, then back off 1.75 turns. Any less than this causes them to overheat where everything expands. Adjust the 13mm handbrake nuts last. They should just touch the brake lever.
Mike

 

[sawyer]

Thanks for the tips folks.
I'll go through it all again and loosen up on the adjustment as that seems to make good sense.

Thanks again, I very much appreciate the help .
Regards,
Russ

 

[sawyer]

OK, now I am searching for info regarding the "equalizer / isolator ?" or "compensator ?" or whatever it is called.
It is the aluminum device that the brake lines go to, then out to the slave cylinders.
Can someone please explain its intended purpose and also how it is intended to function ?
Is there anything in there that can act as a "check" keeping the fluid pressurized at the slave cylinders ?
Thanks much,
Russ

 

[gunnnar7211]

the eqkvaliser is in the system to make the brakse strait
if you have a bit diferent pedal presure it kompensaits that.
it a tube with a disk and some sprigs inside cant see howe
it could hold bak fluid

 

[dave_peters]

I agree with Gunnar, inside is a free floating piston which normally is in the centre allowing fluid to do to either brake from either pedal. if only one pedal is pressed the piston, or shuttle, moves across and ensures that only the brake cylinder for that pedal works. Thats why the pedal always goes down further for individual brakes than when both are used, because of the extra fluid needed to move the shuttle

 

[sawyer]

Thank you very much folks !
Will be working on this problem later this week.
Great job !
Russ

 

[sawyer]

Happy to report that all is OK now.
The master cylinder pistons were not retracting fully due to the a combination of miss-adjustments. The pedal UP position stop screws AND the cylinder push rods were not allowing the pistons to fully retract.

THANKS ALL ! ! ! !

 

[knox]

I've got a 7745 with brake issues, possibly the compensator is stuck, so I thought I'd append to this thread where the compensator's function is explained.

Right brake pedal is firm and I bled it no problem. It activates the right brake.

Left brake pedal is spongy and never builds pressure. When left pedal is pressed both left and right slave cylinders are actuated equally.

Am I right to guess something is stuck in the compensator body? Should I take it apart and try to free it up, or perhaps get a kit to rebuild it?

Thanks.
Knox