Volvo Penta TAD1630G, Руководство по ремонту

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Group 20 Service procedures
8
Torquing with Protractor
tightening (angle tightening)
When torquing with protractor (angle tightening), the fastener
is tightened to a predetermined torque and then turned a pre-
determined angle. Example: a 90° protractor tightening
means that the joint is tightened a further 1/4 turn in one op-
eration after the stated torque has been applied.
Lock nuts
Do not re-use lock nuts that have been removed during dis-
assembly operations as these have reduced service life
when re-used. For lock nuts with a plastic insert such as Ny-
lock
® the torque stated in the table is reduced if the Nylock ®
nut has the same head height as a standard hexagonal nut
without plastic insert. Reduce the torque by 25% for bolt size
8 mm or larger. Where Nylock
®
nuts are higher, where the
metallic thread is of the same height as a standard hexago-
nal nut, the torques given in the table apply.
Strength classes
Bolts and nuts are divided up into different classes of
strength; the class is indicated by the number on the bolt
head. A higher number indicates stronger material. For ex-
ample, a bolt marked 10-9 indicates a higher strength than
one marked 8-8. It is therefore important that bolts removed
during the disassembly of a bolted joint must be reinstalled in
their original position when assembling the joint. If a bolt must
be replaced check in the spare parts catalogue to make sure
the correct bolt is used.
Sealant
A number of sealants and locking liquids are used on the en-
gines. The agents have varying properties and are used for
different types of jointing strengths, operating temperature
ranges, resistance to oil and other chemicals and for the dif-
ferent materials and gap sizes in the engines.
To ensure service work is correctly carried out it is important
that the correct sealant and locking fluid type is used on the
joint where the agents are required.
In this Volvo Penta Workshop manual the user will find
that each section where these agents are applied in pro-
duction states which type was used on the engine.
During service operations use the same agent or an alterna-
tive from a different manufacturer.
Make sure that mating surfaces are dry and free from oil,
grease, paint and anti-corrosion agent before applying seal-
ant or locking fluid.
Always follow the manufacturer’s instructions for use regard-
ing temperature range, curing time and any other instructions
for the product.
Two different basic types of agent are used on the engine
and these are:
1. RTV agent (Room temperature vulcanizing).
Used for gaskets, sealing gasket joints or coating gaskets.
RTV is visible when a part has been disassembled; old RTV
must be removed before resealing the joint.
The following RTV agents are mentioned in the Workshop
manual: Loctite
® 574, Permatex ® No. 3, Permatex ® No 77.
Old sealant can be removed using denatured alcohol in
all cases.
2. Anaerobic agents. These agents cure in an absence of
air. They are used when two solid parts, for example cast
components, are installed face-to-face without a gasket.
They are also commonly used to secure plugs, threads in
stud bolts, cocks, oil pressure switches etc. The cured ma-
terial is glass-like and it is therefore colored to make it visi-
ble. Cured anaerobic agents are extremely resistant to sol-
vents and the old agent cannot be removed. When reinstall-
ing the part, degrease it carefully and then apply new seal-
ant.
The following anaerobic agents are mentioned in the
Workshop manual: Loctite
®
572 (white), Loctite
®
241
(blue).
Note: Loctite ® is a registered trademark of Loctite Corporation,
Permatex
®
is a registered trademark of the Permatex Corporation.