BAD Hydraulic Troubleshooting and How To Avoid It

The Hydraulic Troubleshooting HandbookLong-time ‘Planet Brendan’ citizen Owen Williamson, a farmer from New Zealand, sent me this troubleshooting story from ‘the coal face’:

“I have considerable mechanical aptitude, but at the time of this problem I had little knowledge of hydraulics — something I have since fixed. Anyway, I purchased my first ever brand new tractor. And shortly after the warranty ran out, the tractor suddenly ceased to move forward when in gear and engine revs dropped to low RPMs.

At the time the dealer had shut up shop in my nearest town and my closest dealer was a long way away. So I asked a local tractor mechanic to attend to the problem.

The tractor had a dry clutch, but had a turtle/hare, high/low system that used hydraulic clutch packs to activate a planetary gear system via an electric switch. There was a third clutch pack to engage the PTO.

I thought it likely that something had occurred that meant the pilot signal was escaping back to tank (the diff in this case) and therefore reducing oil pressure to the clutch packs. I didn’t think it would be wear because the onset of the fault was sudden.

The mechanic, instead of testing the pilot oil pressure to the clutches in the appropriate places, made a big assumption. And in doing so broke one of your cardinal rules: Never assume anything. He also broke other rules, such as: Check the easy things first.

He assumed that the clutch pack seals were leaking and ordered 3 new clutch pack kits. He then proceeded to split the tractor in half to install the new seals. The bill for which was in the thousands. Ouch!

Surprise, surprise (no, not really) when he put the tractor back together and started it up, the fault remained. It turned out that the fitting that connected the pilot oil supply to the on/off valve for the PTO clutch pack had fractured, letting the oil flow straight back to tank and reducing available pressure. The necessary replacement part cost less than $40!”

There are two morals to this story. And while you may not need to be told, we all benefit from being reminded. The first, which Owen admits to not being on top of at the time, is: even if you’re not the primary troubleshooter BUT you own the machine and/or are going to pay the bill, you must be able to recognize BAD troubleshooting when you see it. AND call it out for what it is. If you don’t, you’ll pay a hefty penalty, just as Owen did here.

The second moral of this story is you must be very wary of the ‘smartest guy in the room’. Or being that guy. I occasionally get barbs from these folk after they’ve had my 12 irrefutable troubleshooting principles explained to them. And it’s usually something along the lines of: “I’ve being doing hydraulics for 40 years and this (the 12 principles) adds nothing to my enormous body of knowledge.” Trouble is, 5 minutes later this same guy is splitting some poor, unsuspecting farmer’s tractor in half to replace clutch pack seals that are not leaking.

The ‘smartest guy in the room’ is the one most likely to trip over his own ego when troubleshooting. So when you come across him, and you will at some point, keep him on a very tight leash.

That said, it’s always possible that this tractor mechanic was short of work that month and wanted (needed) the job of splitting the tractor in half and replacing the clutch pack seals. But this is an animal of a different stripe. Same result. But different animal. Read or re-read Part 2 of Insider Secrets to Hydraulics for more on recognizing and avoiding this beast when it shows up.

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