# lost brakes on Ford 8730



## westoz1 (Apr 11, 2013)

G'day,
Our 8730 F.W.A Ford loses brake pressure after a couple of days of no use and then the pedal sinks to the floor- no sponginess or softness- just gone. After a couple of hundred pumps on the pedal full and complete braking is restored. The pedal is then solid and does not slowly sink under pressure. If the tractor is used regularly, say every couple of hours then the brakes remain solid. Once it sits for a couple of days then they disappear again. There are no visible leaks, the system has been bled a couple of times and when working works at 100%.

Any help would be much appreciated
Cheers


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## sixbales (May 18, 2011)

Howdy Westoz,

Most likely your brake master cylinder (Hydraulic Valve Assy.) needs a rebuild. See item #29 on the attached diagram. You can buy a rebuild kit and do it yourself, or you can buy buy a rebuilt valve from your dealer.


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## westoz1 (Apr 11, 2013)

G'day sixbales,
Cheers for the schematic. I don't suppose you could post one for the oil feed to the master cylinder and then the pressure to the wheel and the braking mechanism? An idea that I had was like you suggested regarding the master cylinder and I thought that air might be getting in and that let the fluid drain back to the transmission. I then wondered if there was a one way valve in the line somewhere and also how was the oil feed supplied? I haven't tried pumping the brakes without the engine running to test whether supply comes from a pressure system in the trans or if it is lifted via the master cylinder somehow.
Thanks again


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## sixbales (May 18, 2011)

Westoz,

Attached are all diagrams available in the "brakes" section ot the New Holland Library for an 8730. Hope you find what you are looking for.


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## westoz1 (Apr 11, 2013)

G'day sixbales,
Thanks heaps for those diagrams. Now I know a bit more about where and how this particular system works. The master cylinder isn't actually a master cylinder in the historical sense,it doesn't create pressure through foot pressure though it does control things. With the cap off and the engine running, I can see oil being fed from the transmission/hydraulics up to the reservoir and then when it reaches a level it spills over into a return line back to the trans. I can replace the cap, have the brake pedal depressed and crack a wheel bleed screw and a constant stream of oil comes out of the screw. Close the screw up and with a couple of pumps our brakes are 100%. Leave the tractor for a couple of days and we are back to zero again. It seems like air is entering or oil is draining from somewhere and probably inside the brake actuator because there are no visible leaks and the supply side seems to be okay.
???


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## sixbales (May 18, 2011)

Attached is a parts diagram of your 8730's rear differential, including the brake discs and associated components. 

You have a leak somewhere in your brake system allowing air to enter the line(s) between the master cylinder and brake pistons in the rear end. Are BOTH pedals soft?? Do you have to bleed BOTH sides to get the air out? That would indicate a leak common to both sides?? The master cylinder reservoir is common to both, but from there onward they should be two separate hydraulic links??


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## westoz1 (Apr 11, 2013)

G'day Sixbales,
Had another look today after she'd sat for a couple of days. The reservoir level was down maybe an inch or so. After a few minutes with the engine running it was full again. Still no pedal. Pumped a dozen or so times and still nothing. Flicked the brake lock and bled one side. That pedal then worked good but nothing on the other side until I bled it as well. It is interesting how the level in the reservoir can drop without it leaking.


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## sixbales (May 18, 2011)

"The reservoir level was down maybe an inch or so. After a few minutes with the engine running it was full again."

I wonder if your hydraulic pump is losing prime and causing the fluid loss. Does it pump into the bottom of the reservoir, where it can also drain the fluid level? When you first start it up, do the hydraulics work immediately? Or is there a time delay till it gets pumping?


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