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How to Clean VOLVO Diesel Generator Cooling System

Oct. 15, 2019

VOLVO Engine Cooling System

Volvo engine's internal cooling system makes sure the engine works at the right temperature. It is a closed system that must always be filled with a mixture of concentrated coolant and water in order to protect the engine against internal corrosion, cavitation and bursting due to freezing.

Coolant of a suitable chemical composition must be used all year round. This also applies in areas where there is never any risk of freezing, to provide the engine with full corrosion protection. The use of anti-corrosion agents alone is not permitted in Volvo Penta engines. Never use water alone as a substitute for coolant.

The corrosion protection additives become less effective over time, which means that the coolant must be changed at regular intervals; refer to Maintenance Schedule. The cooling system must be flushed whenever the coolant is changed;

Volvo Penta coolants have been prepared to work best with Volvo Penta engines and offer excellent protection against corrosion, cavitation damage, and bursts due to freezing. Only coolants of this quality are adapted to, and approved by, Volvo Penta.



Volvo Penta engines are delivered with either Volvo Penta Coolant (green) or Volvo Penta Coolant VCS (yellow); both are available as concentrates and Ready Mixed.

We recommend that the coolant supplied with the engine on delivery be used. Future warranty claims related to engine and accessories may be denied if an unsuitable coolant has been used, or if the instructions for coolant mixture have not been followed. Engines using yellow Volvo Penta Coolant VCS must have a yellow decal with the text VOLVO COOLANT VCS on the expansion tank.

The two types of Volvo Penta coolant may never  be mixed with each other as this will affect the anti-corrosion properties.

Coolant filters may not be used together with Volvo Penta Coolant VCS.

Ready Mixed

The ready-mixed coolant protects the engine from corrosion damage, cavitation damage and bursts due to freezing down to

-28 °C (-18 °F) Volvo Penta Coolant (green).

-24 °C (-11 °F) for Volvo Penta Coolant VCS (yellow).


Coolant, Mixing

WARNING! All coolant is hazardous and harmful to the environment. Do not consume. Coolant is flammable.

IMPORTANT: Different types of coolant must not be mixed with each other.

The concentrated coolant must be mixed with pure water (distilled or deionized water) according to specifications; refer to Water Quality page 61.

Mix: 40% concentrated coolant and 60% water

This mixture prevents against internal corrosion, cavitation and bursts due to freezing down to

-28°C (-18°F) Volvo Penta Coolant (green).

-24°C (-11°F) Volvo Penta Coolant VCS (yellow).

At 60% glycol concentration, the freezing point is lowered to

-54°C (-65°F) Volvo Penta Coolant (green).

-46°C (-51°F) Volvo Penta Coolant VCS (yellow).

Never mix in more than 60% of the concentrated coolant. A greater volume of concentrate entails a reduced cooling effect with the risk for overheating and reduced anti-freeze protection.

It is extremely important that the system be filled with the correct coolant concentration. Mix in a separate clean vessel before filling the cooling system. Make sure that the liquids mix.

Coolant mixing is not allowed.jpg


Coolant Level, Checking and Topping Up

WARNING! Do not open the coolant filler cap when the engine is hot, except in emergencies, this could cause serious personal injury. Steam or hot fluid could spray out.

Check the coolant level daily before starting. Top off with coolant as necessary. The level should be about 5 cm below the sealing plane of the filler cap or between the MIN and MAX markings if a separate expansion tank is installed.

IMPORTANT! Topping off must take place using a mixture of the same type as that already in the cooling system.

Filling a completely empty system

Check that all drain points are closed.

NOTICE! The location of drain and venting nipples is shown on the next page.

Topping off must be done with the engine stopped. Fill slowly, to allow air to flow out through the venting nipples and the filler.

If a heating unit is connected to the engine cooling system, the heat control valve must be opened and the installation vented during filling.

IMPORTANT! Fill up with coolant to the correct level. Do not start the engine until the system is vented and completely filled.

Start the engine and warm it up until the thermostats are fully open (about 20 minutes). Open any venting nipples a short while after starting, to allow trapped air to escape. Check the coolant level and top up as necessary.


Coolant level checking.jpg


Drain/bleed cocks, Location

Drain plugs (P)

- beneath the radiator

- next to cylinder #3 and cylinder 5 (on 4 and 6-cylinder engines)

- beneath the coolant pump (does not apply to 420–733)

- beneath the oil cooler

Venting nipple (1):

- on the coolant pump


Bleed cocks.jpg


Charge Air Cooler, External Cleaning

Remove guards as necessary, to access the radiator. Clean with water and a mild detergent. Use a soft brush. Be careful not to damage the radiator vanes. Reinstall removed parts.

IMPORTANT! Do not use a pressure washer.

Charge air cooler cleaning.jpg



Cooling System, Cleaning

Cooling performance is reduced by deposits in the radiator and cooling galleries. The cooling system should be cleaned out when the coolant is changed.

IMPORTANT! Cleaning must not be done if there is any risk of the cooling system freezing, since the cleaning solution does not have any antifreeze properties.

IMPORTANT! It is extremely important that the correct concentration and volume of coolant is added to the system. Mix in a separate clean vessel before filling the cooling system.

Make sure that the liquids mix.

1 Empty the cooling system. Refer to Coolant, Draining.

2 Put a hose into the expansion tank filling hole and flush with clean water, as specified by Volvo Penta refer to section Water quality in  Technical Data page 60 until the water draining out is completely clear.

3 If there should still be some contamination left after flushing for a long time, cleaning can be done with coolant. Otherwise, continue as in item 8 below.

4 Fill the cooling system with 15-20 % mixture of concentrated coolant. Use only Volvo Penta recommended concentrated coolant mixed with clean water.

5 Drain the coolant after 1-2 days of operation. Remove the filler cap and possibly the lower radiator hose to increase the speed of emptying. To prevent suspended material from settling back in the system emptying should be done rapidly, within the space of 10 minutes, when the engine has not been standing still for a long time.

6 Flush the system immediately and thoroughly with clean hot water to prevent dirt from settling in the inner areas. Flush until the water that runs out is completely clean. Make sure that any heater controls are set to full heating during emptying.

7 If contamination should still be left after a long period of flushing, cleanout using Volvo Penta radiator cleaner, followed by finishing-off with Volvo Penta neutralizer. Carefully follow the instructions on the package. Otherwise, continue as in item 8 below.

8 When the cooling system is completely free from contamination, close the drain taps and plugs.

9 Fill up with Volvo Penta recommended coolant.

Volvo diesel engine.jpg

NOTICE! The global famous Volvo company was established in 1927. It is Sweden’s largest industrial enterprises and also one of the world’s oldest engine manufacturers. The engines adopt full electronic fuel injection control technology, with high performance and high reliability. They have the merits of good startup performance, voltage stability, reliable operation, low emission and low noise. Our company was authorized as VOLVO diesel generator set OEM, providing 85KVA to 750KVA Volvo diesel genset including open type, silent type and trailer type generating set.

silent gensets

More information about Volvo geneator set information, please read this article: Volvo Generator Introduction--Volvo Diesel Generator

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