M hydraulic cap

Mark Poss · Sep 18, 2022

I was driving the M over some rough ground and noticed oil coming out of the hole in the cap. Im assuming the hole is a vent but should there be something else in there to keep oil from coming out? Thanks for any help, Mark

Charlie M · Sep 18, 2022

Unless you have something plumbed we can't see in the picture that is a cap that would go where you fill the pump with oil and its currently attached to where a hose would hook up for an implement. I would think if you used the hydraulic system it would spray oil out the hole every time. In addition if the cap was put where it should be it shouldn't have that hole on top either. Someone has added it to be a vent for some reason. I'd take it off and just cap the outlet. What is covering the hole where you add oil?

Mark Poss · Sep 18, 2022

I think just a plug. Ill look tomorrow

D Slater · Sep 18, 2022

Does it have a hydraulic pump on engine added. The cap is for a belly pump in conjunction with a IH type remote control valve. Really a bleeder valve like used on some diesel engines. Missing the top screw. Regular cap just has a small hole and both types used filter material in cap. Don't know what you have, but a side vent pipe is sometimes added with fill cap when belly pump is gutted, and engine pump installed. If belly pump is working it would send oil under pressure out the cap if used.

used red MN · Sep 18, 2022

For one that cap has been modified, but it probably makes no difference. Originally no fitting in it just a 1/16 inch or slightly larger hole. If you have a live pump and the internals of the belly pump have been removed to use the lift all as a reservoir then that port will not be pressurized. The normal fill Charlie mentions comes through the torque tube in a location sort of opposite of the starter. The cap on my M is there is has some type of fiber mesh in it. It seem similar to a cut up scotch bright pad. My M has a live pump.

Mark Poss · Sep 18, 2022

Yes it has a hydraulic pump on the engine. The guy I got it from said it has live hydraulics

D Slater · Sep 18, 2022

Cap was used with this attachment. Unless to high oil level vent should work in present location. Aftermarket vent caps with opening in caps under bonnet works and have filter material or screen. If oil is returned to unit above oil level it can cause oil to spit some out the vent. That IH system would do the same thing is the reason the hole could be closed in cap after air was removed when using valve for two way operation.

BarnyardEngineering · Sep 19, 2022

(quoted from post at 16:27:15 09/18/22) Yes it has a hydraulic pump on the engine. The guy I got it from said it has live hydraulics

Ok that means that the belly pump has probably been converted to be used as a reservoir.

Where that fill cap is attached, is normally a pressure output port.

Oil expands in volume when heated so if you recently topped off the reservoir to the tippy-top the oil expansion and a little bit of rough going could cause oil to come out that cap. Also if you hooked up to a cylinder that was extended, and retracted it, that would put extra oil into the reservoir, even if two-way.

You do NOT want to plug that hole if you are using the hydraulics. Air needs to enter and leave the system as the oil is pumped out to the cylinders and back in. Air needs to come in and leave to make up for the change in volume of hydraulic fluid even for two-way cylinders.

There is a significant difference in volume between the rod end and piston end of the cylinder.

M hydraulic cap

Mark Poss

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Charlie M

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Mark Poss

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D Slater

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used red MN

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Mark Poss

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D Slater

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BarnyardEngineering

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