1998 Land Rover Workshop Manual

26
COOLING SYSTEM
VISCOUS FAN
Description
Operation
The viscous unit consists of two principal components:
An inner member 1 which is secured to water pump
spindle and is driven by the fan belt.
An outer member 2 which has the fan blades
attached, houses the working parts and is driven
through the medium of the viscous fluid.
The viscous drive unit for the engine cooling fan,
provides a means of controlling the speed of the fan
relative to the running temperature of the engine. The
viscous unit is a type of fluid coupling, which drives
the fan blades through the medium of a special
’silicone fluid’ injected into the unit during
manufacture.
The inner and outer members have interlocking
annular grooves machined in each, with a small
running clearance 3 to allow the silicone fluid to
circulate through the valve plate 4.
The unit also contains a valve 5 which is controlled by
an external bi-metal thermostat 6.
Starting engine from cold
During the time the engine is at rest the silicone fluid
drains down, half filling chambers A and B. Thus when
the engine is first started sufficient fluid is present in
chamber A to provide a positive drive between the
members, as is evident by the initial noise of the fan.
However within a very short period of time, after
starting the engine, the fan speed and noise will
decline indicating that the fluid is being centrifuged
into chamber B (as seen in RR3757M) causing the
drive to slip.
1.
2.
3.
Drive in from water pump spindle
Drive out to fan blades
Bi-metal
2
DESCRIPTION AND OPERATION
Product Specification
CategoriesRange Rover
Tags
Model Year1998
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- 873 pages
Document TypeWorkshop Manual
LanguageEnglish
Product BrandLand Rover
Document File TypePDF
Publisherlandrover.com
Wikipedia's Pagehttp://en.wikipedia.org/wiki/Land_Rover
CopyrightAttribution Non-commercial
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