mf 70 no brakes

mf70

New member
i've got a mf 70 backhoe with no brakes.There is a hydraulic pump for the rear brakes, how can i tell if this is working?
 

Gary66

Member
I'm not familiar with your tractor, and I'm a simple sort of clod...but, I generally think of hydraulic pumps in association with steering, (or a working implement of the tractor), and perhaps a vacuum booster for brakes. A hydraulic PUMP with control etc. should provide some serious stopping power, which means pressure. Install a pressure gauge in the line to see what happens when the control is activated...or try stopping.

A simple test might be to crack the hydraulic line connection at a wheel and provide a clean container to catch fluid. Then activate the brake without the engine running. Note what happens. Then run the engine and activate the brake and see if something different happens. I'm thinking that you should get a real gusher with the engine running. If not....the pump, control or lines have a problem. Remember to close the line while fluid is still running to prevent air from entering.

You might also run the engine and crack the return line (from the control) at the reservoir. If fluid is running, the pump must be pumping and the control is recirculating it back. Your pump may have a pressure relief valve inside the pump, but there should be fluid circulating thru the control.

You might just jack it off the ground and see if you can turn a tire. Have someone activate the brake as you rotate the wheel and see if it stops. Try this with engine running and without it running. I suspect you should hear something if anything is moving within the brake mechanism. If not...hold a broomstick or something against the brake housing and to your ear. That should make it easier to hear or feel movement vibrations.

Also, you could install a shutoff valve after the pump, but before the control. With engine running, slowly close off against the pump. A pump that is working should make a bit of a fuss. Open the valve if you hear or feel a change...don't want to break anything! Happy testing
 

mf70

New member
there is very minimal brakes if the pedal is pumped with the engine off, the differential lock is also run by the same pump and does not work either, I plan to find the filter this weekend and see if it has any fluid in it.
 

Gary66

Member
Here is some info from this site: http://www.ytmag.com/cgi-bin/store/model_parts.cgi?SearchArea=MF&&md=70&r=zone &pics=1

I was unable to display the site picture of the 3-position spool, but you should see it at the above address when you click to show pictures. I suspect this is a "new" tractor to you, so don't be offended...but the problem may be as simple as changing a switch position. Brakes and differential lock mechanisms should be one-way cylinders, so according to this site info, (if your tractor does not have individual external hydraulic systems), you would need the control spool in the forward position. The picture showed a lever on the spool.

Hydraulic Selector, isolator assembly - For tractors without individual external hydraulic systems. Three-position spool, forward position allows one-way (push) for single acting cylinder. Center position allows operation of the 3-point arms, & the rear position will feed power to a 4-way control valve for two-way (push-pull) operation of double acting cylinder. Fits all MF tractors where 182373M1 lift cover is used. Replace MF cover plate, adds 2 ports I\O ports 3\8: NPT. (Part No: TS300) $94.12 [Enlarge Picture]
Hydraulic Valve Manifold - This 3 Spool Valve Allows Operator To Use Aux. Hydraulics at the same Time Without Valve Switching. Some Tractors may need slight modification on seat.Includes 2 elbows. Models from 1960 and later years. (Part No: 19833A92) $627.00 [Enlarge Picture]
Selector Valve, 3 Way - NIS - A&I Replaces cover plate 180908M1, adds 2 ports. Services lift arms plus 2 external ports with return going back to valve, ports can only be used 1 at a time, 3\8 NPT ports. (Part No: 47S731) $94.58 [Enlarge Picture]
Valve - Valve for TS3200M. Single spool, 4-way, 3-position, spring loaded to neutral. No relief valve, no power beyond option. In & out ports 3\4", work ports 1\2" NPT. (Part No: TS200BA) $163.60 [Enlarge Picture]
 

mf70

New member
the brake/diff lock pump is on the back of the power steerin pump (also a gear driven hydraulic pump) the brake pump is driven by the power steerin pump. The fluid for the brake pump comes from the rear differential, the priority flow is for the brakes (2000) psi)and secondary flow is for the diff lock(190 psi). there doesnt appear to be any pressure coming out of the pump, so i need to figure out why. I have'nt been able to find the filter but there must be one someplace, its difficult to follow the supply line because of how its routed.
 

Gary66

Member
Since I'm the only one responding I should disclose my supreme qualifications: I'm dummer'n a post and have no experience relative to this problem...but I ain't completely stupit. I own antique hand-crank tractors, a Model A, several old garden tractors one of which has hydrostatic drive. I'm sure you aren't running 90wt gear oil from your differential, so I'll presume your drive is hydrostatic. If so....the filter would be relative to that drive system. I put a gauge on my hydrostat once and I think it produced about 1,000psi...which wouldn't suffice for brakes that require 2,000psi (as I think I understand from you). That might explain why there is a separate pump for the brakes. Just for grinns, check your fluid level in the differential...there may not be a sufficient level to supply that brake pump. Then crack the line connection at the brake pump to see if fluid is getting there. You certainly wouldn't want any air due to low reservoir (differential) levels.

It's been a few years since I autopsied a power steering pump, but I recall that there was a pressure control component which simply recirculates the fluid and perhaps one other control. I modified it and blew my test system to smytherines. It was a moment to remember. In your case, mayhaps a control valve in the brake pump has stuck. I think that less likely than simply a shortage of fluid, but, it may be the case. The controls seem to be simple ball and spring arrangements so be brave and gut it if needs be.

Being the dolt that I am, and generally unwilling to spend money to "fix" stuff, I would bypass that brake pump and see what kind of stopping happens with the hydro-stat pressure. Just slowing down is acceptable to me...and is actually better than the foot-drag that I depend on now. It's amazing how quickly you can drop the box-scraper (or whatever) when you're hurtling down a 45 degree cliff!
 
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