the hydraulic oil is never, in the words of Martha Stewart, a good
thing. During those sudden cold snaps which accompany winter
weather, water in the hydraulics can turn into ice. Ice inside the
hydraulic system causes acute, dramatic failures which can take you by
surprise when you go out to do the first tow of the day on a cold winter
Water often enters
the hydraulic system gradually over time in the form of rainwater through
the filler neck. When the hydraulic filler cap is missing or has been
replaced with rags stuffed in the hole or no longer
screws into the neck properly, it doesn't always keep rainwater out.
Since oil floats on top of water, the water settles into the lowest point
in the hydraulic system. On many tow trucks, the lowest point is the
large-diameter rubber suction hose that supplies hydraulic oil to the
Then, the temperature drops from
above freezing to the single digits and stays there throughout the
night. By morning, the water in the suction hose has turned into a
solid plug of ice. The tow truck operator engages the PTO for the
first tow of the morning, and the hydraulic pump burns out from total oil
Keep ice and water out of the
hydraulic system by using a filler cap that stays on. If you suspect
water in the hydraulic system, you can sometimes drain it out by undoing
the lowest point in the system and watching what comes out.
Milky-looking hydraulic oil usually means water's been in the system and
has been churned around with the oil.