John Deere 7210 Rear SVC Issue

[GaryBDavis]

John Deere 7210 with dual rear SCVs, standard three position (extend-neutral-extract). These are the fancy ones in a stacked configuration with speed and function controls (auto/manual/no detent) and the test ports.

Rear SCV Issue
SVC1 started to bleed down, I replaced the check valves in the SCV and it seemed good for a short time but then the issue came back. Currently, SVC1 bleeds down and will not hold the implement cylinder if it痴 under gravity load. Also, when I put it under a heavy load, it blows the hoses out of the couplers from both SVC1 an SVC2. That痴 right, it blows all four hoses out, not just the ones hooked up to SVC1. When this happens, I can see the female couplers in the housings push out like there is a high amount of pressure behind them. Kind of like watching someone痴 eyes bulge out.  If you watch real closely, you can see these female couplers move in and out when you connect and disconnect hoses so they are meant to do that, just not when one of the SVCs hits full pressure. SVC2 works like it should so nothing is wrong with it.

I have the shop manual (test and repair) for this tractor and it has all of the tests laid out in detail. Problem is, I don稚 have the manifold test gauge set it takes to do the diagnostic work (JT07115) and that痴 like a $1k kit.

I did a full hydraulic service about 200 hours ago. Completely drained and replaced (new) the trans-hydraulic fluid, filters, cleaned out the pickup screen. etc. It all looked pretty clean.

My plan is to find someone locally who works on tractor hydraulics and has the tools to diagnose it. I値l probably let them do the repair as well. Taking to the JD shop will be the last resort.

I hoping to find someone here who has 都een this before and can tell me 妬t痴 a common problem/fix and I can do it myself.

Thanks,
Gary

 

[Tx Jim]

My knowledge of JD tractors built after '92 is limited. Have you checked stand-by pressure? According to Tractordata pressure should be 2900 psi. Does your tractor have breakaway similar to photo? If so I wonder if an internal o-ring could be leaking letting pressure leak by inside coupler? If tractor was mine I might be tempted to install older type breakaway coupler that one had to slide collar rearward to connect/disconnect hoses.

 

[GaryBDavis]

No I haven't checked the standby pressure. I don't have a gauge but if it's just a simple hydraulic pressure gauge with a quick disconnect, I could make one (steal the pressure gauge from my log splitter). Just plug it in to each port, bottom out the lever and read the gauge? The couplers are built into a housing and not screwed on like the one in your picture. I can buy a rebuild kit for them that contains all the internal parts.

One more hint I can give is that I can physically hold the hoses/connectors in while someone in the cab operates the levers and all is good. And no, I'm not superman.