Oil Cooler; Description; Oil Temperature Switches; Maintenance - Manitowoc Grove RT770E Service Maintenance Manual

RT770E

OIL COOLER

Description

An air cooled hydraulic/transmission oil cooler (Figure 2-3) is
located next to the hydraulic tank. The front section is the
transmission oil cooler and the rear section is the hydraulic

oil cooler.

The hydraulic driven fan pulls cool air through the cooling
fins on the cooler. Normally, the hydraulic oil coming from the
different components is routed through the oil cooler by way
of a return line, and on to the filter in the reservoir. When
several hydraulic functions are being used at one time (i.e.,
hoisting, lifting, and telescoping), more oil has to flow
through this return line, causing a pressure buildup. When
this pressure reaches 1.0 bar (15 psi), the normally closed
check valve in the return line (in parallel with the return line
through the hydraulic oil cooler) will open, letting some
hydraulic oil bypass the hydraulic oil cooler and flow directly
into the reservoir filter.
When fewer functions are being used, the pressure in the
system will decrease below 1.0 bar (15 psi) and the check
valve will close again.

Oil Temperature Switches

A hydraulic oil high temperature indicator switch (4),
Figure 2-1 and two oil cooler fan motor temperature switches
(6 and 7) are installed in the return tube. The two oil cooler
fan motor temperature switches are normally closed at low
oil temperatures. When the hydraulic oil temperature
reaches 48.9°C (120°F), one of the oil cooler fan motor
temperature switches will open, causing the CAN bus
system to turn on the oil cooler fan motor to its low RPM
setting. When the hydraulic oil temperature reaches 71°C
(160°F), the other oil cooler fan motor temperature switch will
open, causing the CAN bus system to increase the RPM of
GROVE
the oil cooler fan motor to high. The hydraulic oil high
temperature indicator switch is normally closed and will open
when the hydraulic oil temperature reaches 87.8°C (190°F),
causing the CAN bus system to turn on the hydraulic oil high
temperature indicator in the gauge cluster to alert the
operator to the condition.
The temperature switch (5, Figure 2-3), located in the inlet
tube of the transmission oil cooler, is part of a circuit that will
alert the operator to a high transmission oil temperature
condition. The switch is normally closed and will open and
cause the circuit to lose ground when the transmission oil
temperature exceeds 93°C (200°F). When the circuit loses
ground, the CAN bus system will turn on power to illuminate
the Transmission Warning Indicator in the gauge display in
the operator's cab. See Section 3 - Operating Controls and
Procedures, in the Operator's Manual for details of the
Transmission Warning Indicator.

Maintenance

The oil cooler should be checked daily for dirt buildup, as a
dirty cooler will result in high oil temperatures. High oil
temperatures will reduce the performance and useful life of
the oil, which can ultimately result in component failure.
If the cooler is contaminated with dust, it can be cleaned
using compressed air. If the cooler is contaminated with a
mixture of oil and dust, it should be disassembled and
treated with a liquid cleaner, then cleaned of debris using
compressed air. Take care when using compressed air, a
high pressure washer, or a steam cleaner, as the fins of the
cooler may be damaged. To ensure effective cleaning, the
direction of air, water, or steam must be opposite to the
direction of normal airflow through the cooler. On cranes that
operate in corrosive environments (salt), frequently clean the
cooler with water to help prevent corrosion.
Published 11/26/2014, Control # 447-05
HYDRAULIC SYSTEM
2-15
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