Remove grease and scale in the cooling system

AR20.00-B-1030XA

Remove grease and scale in the cooling system

03.02.2020

Engine

902.9 in model 384.06

Engine

904 in model 384.201/223/334, 688.276/277

Engine

906 in model 382.175/188

Engine

924 in model 384.311/333

Engine

926 in model 382.171/176/177/180/181/185/188/189

1

Equalizing tank cap

2

Engine block drain plug

3

Drain plug on the cooler

4

Thermostatic valve

 Warning

Risk of injury to skin and eyes suffering scalding from contact with hot coolantspray. Risk of poisoning from swallowing coolant.

Do not open cooling system unless coolant temperature is below 90 °C. Open cap slowly and release the pressure. Do not pour coolant into beverage containers.
Wear protective gloves, protective clothing and safety glasses.

AS20.00-Z-0001-01A

1

Remove the equalizing tank cap (1)

2

Remove the plugs from the engine block (2) and cooler(3) and drain the coolant



Engines 902.9, 904, 906, 924, 926

AP20.00-B-2080-01B

 If the vehicle is equipped with heating, actuate the command to the open position.
Install the plugs on the engine block and cooler, after completely draining the coolant.
Dispose of the coolant in an eco-friendly manner.

3

Remove the original thermostatic valve (4) and install a blocked thermostatic valve in the maximum opening position



Blocked coolant thermostat valve for cleaning

.

WF58.50-B-2002-01A

Engines 904, 906, 924, 926,

AR20.10-B-2460XA

 The blocked valve allows full circulation of the fluid through the cooling system at any temperature.
The blocked valve allows full circulation of the fluid through the cooling system at any temperature.

Engines 902.9, 904.9, 906.9, 924.9, 926.9Main valve

*BE20.10-B-1002-02B

4

Reinstall the plugs on the engine block (2) and cooler (3)

5

Fill up the cooling system with a degreasing solution

 Do not use caustic soda (sodium hydroxide) or other very alkaline product. These products attack the aluminum parts of the cooling system.

 Degreasing the cooling system is recommended when the coolant is contaminated with lubricating oil

 Degreasing solution:
Clean water and 5% of degreasing product (50 g of product for each 950 g of water).

 Warning

Risk of accident from vehicle starting off by itself when engine running. Risk of injury (bruises and burns) resulting from working on the engine while it is being started or when it is running.

Secure vehicle to prevent it from starting off by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.

AS00.00-Z-0005-01A

6

Run the engine at medium speed until it reaches 80 oC, and keep it at this temperature for 20 minutes

 Make sure the gearbox is in neutral.
Utilize appropriate clothes and pay attention to the engine's heated-up and moving parts.
If necessary, cover the cooler to control the desired temperature.

7

Remove the plugs from the engine block (2) and the cooler (3) and drain the solution



Engines 902.9, 904, 906, 924, 926

AP20.00-B-2080-01B

 Before you drain the solution, stop the engine and wait until the temperature cools down to 50 oC lower. After completely draining the solution, install the drain plugs.

 Dispose of the solution in an eco-friendly manner.

8

Reinstall the plugs on the engine block (2) and cooler (3)

9

Immediately fill up the cooling system with clean water and run the engine for 5 minutes

 Stop the engine and wait until the temperature cools down to 50 oC. Drain the system, fill with clean water again and tun the engine for additional 5 minutes.

10

Stop the engine and completely drain the cooling system



Engines 902.9, 904, 906, 924, 926

AP20.00-B-2080-01B

 Draining the cooling system when the coolant temperature is below 50 oC.

11

Reinstall the plugs on the engine block (2) and cooler (3)

12

Fill up the system with a descaling/deoxidizing solution

 When, under normal operating conditions, the engine shows a overheating trend without apparent reasons, descaling and deoxidizing the cooling system is advisable.

 Descaling solution:
Clean water and 10% citric acid (100 cubic centimeters of citric acid every 900 g of water).

Citric acid powder (0.5 kg)

*BR00.45-Z-1070-04A

13

Run the engine at medium speed until it reaches 80oC, and keep it at this temperature for 10 minutes

 If necessary, cover the cooler to control the desired temperature.

14

Remove the plugs from the engine block (2) and the cooler (3) and drain the solution



Engines 902.9, 904, 906, 924, 926

AP20.00-B-2080-01B

 Before you drain the solution, stop the engine and wait until the temperature cools down to 50 oC lower. After completely draining the solution, install the drain plugs.

 Dispose of the solution in an eco-friendly manner.

15

Reinstall the plugs on the engine block (2) and cooler (3)

16

Fill up the cooling system with clean water and run the engine for 5 minutes

 Stop the engine and wait until the temperature cools down to 50 oC, and drain the system.

 Do step (12) three times.

17

Remove the plugs from the engine block (2) and the cooler (3) and drain the solution

18

Reinstall the plugs on the engine block (2) and cooler (3)

19

Check the operation of the thermostatic valve (4)

Engines 904, 906, 924, 926,

AR20.10-B-2455XA

20

Install the original thermostatic valve (4)

Engines 904, 906, 924, 926,

AR20.10-B-2460XA

21

Fill the cooling system

Topical note

Notes on coolant

AH20.00-N-2080-01A



Engines 902, 906, 904, 924, 926,

AP20.00-B-2080XA



Engines 904, 906, 924, 926,

AP20.00-B-2080D

Coolant thermostat

Number

Designation

Engines 902.9, 904.9, 906.9

Engines 924.9, 926.9

BE20.10-B-1002-02B

Main valve

Maximum opening

o C

95

95

Minimum stroke

mm

8

8

Repair materials

Number

Designation

Order number

BR00.45-Z-1070-04A

Citric acid powder (0.5 kg)

A 000 989 10 25