1998 AUDI A8 coolant

19-23

Thermostat, removing and installing


Notes:

Always replace seals and gaskets.
Cover the toothed belt with a cloth to protect it
from coolant before removing thermostat.

Removing

- Drain coolant page 19
-11
.

- Remove front bumper.

Repair Manual, Body Exterior, Repair Group
63


Lock carrier in service position

Repair Manual, Body Exterior, Repair Group
50


- Remove ribbed belt page 13
-8 .
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19-24

Installing
Installation is the reverse of removal, noting the
following:

Bleeder valve for thermostat (arrow) must be at the top.
- Install thermostat -4- into engine block.
- Moisten new O-ring -3- with coolant.

- Install connection -2- for thermostat and tighten bolt -1- to 10 Nm (7 ft
lb).
- Install and tension toothed belt page 13
-12
.
- Install ribbed belt page 13
-8 .
- Fill cooling system with coolant page 19
-11
.
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19-26

Coolant fan, checking


Test requirements

Test procedure
Fuse No. 34 OK Coolant Fan Control (FC) thermal switch -F18- OK
- Disconnect 3-pin harness connector from coolant Fan Control (FC)
thermal switch -F18- at bottom left of radiator.
- Switch ignition on.

- Bridge terminal -1- and terminal -2- of harness connector using
auxiliary cables from VW1594 connector test kit.
Coolant fan -V7- must run on 1st speed.
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19-27


If 1st or 2nd fan speed does not run:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no open circuit can be found: - Bridge terminal -1- and terminal -3- of harness connector using
auxiliary cables from VW1594 connector test kit.
Coolant fan -V7- must run on 2nd speed.
- Locate and repair open circuit using wiring diagram:- Replace coolant fan -V7-.
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19-28

Cooling system, pressure test


Engine at operating temperature

WARNING!

The cooling system is pressurized when the
engine is warm. When opening the expansion
tank, wear gloves and other appropriate
protection, cover the cap with a cloth and
open carefully to relieve system pressure
slowly.

- Open cap on coolant expansion tank.

- Using VAG1274/8 adapter attach VAG1274 cooling system tester to
coolant expansion tank.
- Use tester hand pump to create a pressure of approx. 1.0 bar (14.5
psi).
- If pressure falls, check for leaks and repair.
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19-30


After-run coolant pump

1 -
Coolant reservoir
Perform coolant system leak test using
VAG1274 cooling system tester and
VAG1274/9 adapter.
2 -
Lower coolant pipe
3 -
25 Nm
4 -
25 Nm
5 -
Bracket for after-run coolant pump
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19-31


6 -
Spring clamp
7 -
Coolant hose
8 -
Spring clamp
9 -
Electrical after-run coolant pump
Checking page 19
-32
Removing and installing page 19
-34
10 -
10 Nm
11 -
Spring clamp
12 -
Coolant hose
13 -
Spring clamp
14 -
Connection
For thermostat
15 -
Oil cooler
16 -
Oil filter
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19-32

After-run coolant pump, checking


Note:

Control modules with an after-run time of 15
seconds after engine is turned off were installed
since start of production. As a running change
in m.y. 1999, control modules with an after-run
time of 3 minutes were installed.
The coolant after-run pump also continues to
run after the engine is started again before the
15 second or 3 minute cycle is completed.
The coolant after-run pump and the after-run
fan are controlled via the same control module.
After switching off the engine, the after-run pump
always runs for 15 seconds or 3 minutes after the
engine has been switched off. If during this time
the switch-on temperature of 102 C (coolant
temperature) is reached at the thermostat of the
second fan stage, the after-run pump continues
to run and the coolant fan continues to run in the
after-run stage until the switch-off temperature of
91 C of the coolant at thermostat has been
reached. The maximum running time of the after-
run pump is 10 minutes.
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11/21/2002 htt
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pair&id=AUDI.B5.GE03.19.1