JD 318 Model 30 Hydraulic Tiller problem. Need Help!

I have a problem with the oil pumping out of the reservior tank, it is coming out fill spout. To begin with I made sure it was only filled to the cold level. At first everything sound good and the tiller is working great. Then I start to hear noise, I believe it is coming from the pump and then after tilling for about 5 minutes the oil start coming out of reservoir tank. The pump is the one that mounts under the John Deere 318 and is driven off the mule drive. Any ideas? Thanks, Jack
 
Are you using the fluid that John Deere specifies?

Is it possible that you have a loose hose connection between the reservoir and the pump inlet? If so, that will allow air to get sucked in and cause the oil to foam. The foam will rise up in the reservoir and weep out of the vent hole. Run the tiller until you see the oil coming out and then open the fill cap to see if foam is present. Hardened hoses or the wrong type of hose clamp can cause this problem.
 
You need to establish first that foaming is the problem. As I said before, go do some more tilling and make the oil come out of the reservoir cap. As soon as you see that happening, just jump off the machine while it is running and remove the cap with gloves on so you don't burn yourself. You should see the foam if that's what's happening.

The pump makes the foam because fittings or clamps are not tight and outside air gets sucked into the pump's intake. Just because a hose isn't drooling oil doesn't mean that air isn't getting into the system. Hoses can be porous. Hoses can get so hardened over time due to hot oil that it's hard to make them seal. Using the wrong clamps (worm gear) can cause the problem too.

Using the wrong oil can cause foaming and that's why I asked you about what you were using.
 
Tom, Thanks for sticking with me.
When I first started out the oil was a little low, also I didn't see any water in the oil. So I checked the operator's manual and used the correct oil that it recommended.
Both hoses checked out and seem to be in good condition.
Now here is where I found the problem, it was as you suggested a loose fitting on the return hose that connects directly to the pump. It looks like there is an o-ring underneath the washer where the nut tightens up against the pump housing.
After I tightend the nut, I tilled for about the an hour and it work great with no noise or foam. So, Tom, Thank you very much for all of your good advice. Jack
 
No problem. Happy to help you find the problem and to hear that your tractor is performing well for you once again.
 

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