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1987 420 Hydro Air Leak at Front Couplers

554 Views 1 Reply 2 Participants Last post by  dhager4692
I ordered a new 420 front bracket for my JBSR front bucket to convert it from my 318 to my 420. The JBSR never ran out of lift power on the 318, but I have noticed on the 420 that it can only lift a half bucket of dirt for example, otherwise it simply won't lift without a lot of effort.

So I started inspecting the front end, and noticed hydro fluid squirting out of the front left couplers. The O-Rings are clearly leaking. So, the question is, since these O-Rings were leaking, would that have introduced air into the hydro system of the 420, thus reducing lifting performance even though the fluid is leaking outside the system while in use? And if so, is there a bleed procedure I need to follow? Is there something on the 420 hydro system where I can enhance pressure or bleed the system other than burping the system?

I ordered 4 new JD 113 O-Rings, and I hope they hold the pressure without leaking once I install them. Any thoughts guys?
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I think that getting the o-rings replaced will help. The leaking o-rings is what limited your lifting capacity. The extra pressure went around the o-ring to the outside.

The hydro pump pulls it oil from the rear differential at a low level in the system. The oil from the hydraulics drains in at a higher level. I do not think you have air in the hydro pump unless the oil level has dropped significantly. The cure is to bring the hydro/transmission oil level to the proper level, the middle of the sight tube that is on the rear of the differential.
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