Dealing with the circumstances leading up to a hydraulic lock on my Bolens tractor engine

August 27, 2015

Instead of my usual couple of hours of indolent reading this morning I resolved to collect a trailer-load of scaffold to erect for a job at the rear of the stone house.

After carefully wiping the dew and dust off my beloved 17 hp Bolens G174, I fired it up and hurried around to the front of the house through a narrow gate on a steep side-hill. Somehow it slipped my mind for the moment that the attached trailer was eight feet wide and weighed about as much as the little tractor. It reminded me of these principles of physics and geometry when one corner of the trailer discovered a forgotten elm stump. Contact with this sturdy object immediately stopped the right side of the trailer’s forward progress. Whatever remained of the trailer’s momentum was then imparted to its tongue, which veered sharply to the right. Of course the tongue was attached by a 2″ ball to the tall, narrow little tractor on a side hill, so it obligingly flipped over, sending its operator on an exhilarating nose-first slide down a well-kept, but steep lawn. In the same motion the Bolens wiggled its hitch ball out of the trailer’s coupler and came to rest upside down, purring contentedly. Your narrator scrambled back up the hill and shut the engine off.

I was unhurt, and the Bolens didn’t seem to have bent anything I couldn’t readily straighten. It remained, however, upside down at a 3/4 cant on a fairly steep slope.
After some reflection I drafted the Kubota B7510, a 4WD, 21 hp compact tractor, to aid its fallen comrade. I parked it nose-down toward the Bolens, then attached a logging chain to its front hitch and the other end around the near axle of the accident victim. My wife eased the Kubota back up the slope in 4WD and the Bolens flipped over onto its wheels as willingly as it had left them.

We coasted down to a low spot and I assessed the damage. One sheet metal brace for hydraulic controls bent back into shape. That was it. The loose hood had survived the fall amazingly well, and the engine didn’t leak oil, coolant, or fuel. It wouldn’t turn over on the starter, though.

I had anticipated hydraulic lock, a diesel phenomenon whereby a cylinder fills with fluid and can’t release the fluid to turn over because it’s on the compression stroke. When the engine was upside-down, crankcase oil had nothing to keep it from flowing down through any open valve into the cylinders.

The Kubota and my wife towed us up the hill to the garage, but not inside, fortunately.

A quick Internet search suggested removing the glow plugs to let the oil out of the affected cylinder, so I dutifully found a 12mm socket with extension, removed the little plugs (only one wet with engine oil), and prepared to clear the cylinders. I carefully placed a rag over the twin openings in the top of the engine to keep things tidy, but at the first touch of the starter a narrow gush of black oil shot the rag high above the tractor before turning its propellant into a comic deluge of large, black dollops of oil.

This provided a great way to break in a too-new Tilley, but the clean-up of the equipment and wardrobe afterward quickly became a chore.

The 1980 Bolens soon was back in service, down a bit of oil and very dirty, but still willing to do a day’s work.

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3 Responses to “Dealing with the circumstances leading up to a hydraulic lock on my Bolens tractor engine”

  1. Keith Cauwenberghs Says:

    I do have to admit that your stories are always entertaining and thankfully you were not hurt. I can see the oil shooting out of the cylinder like a geyser and it must have been quite the surprise. I suppose you could say at this point is: “all’s well that ends well”.

  2. Tom Says:

    I’m surprised you had this event. Know you to be smarter than that. Every bad move I make, I make when in a hurry. Tilley hats replaceable. There will never be another Rod Croskery.

    On banks, I always approach from downhill. But have observed my Tundra corners better (less lean) when towing a heavy load……level road tho.


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