Mercedes-Benz ML320. Manual — part 634

If the chloride or total ionic content of the water is too high, then the level can be reduced through the
admixture of demineralized, in other words, ion-exchanged or distilled water.

Particular treatment processes will need to be used (desalination and demineralization or subprocesses)
depending upon the contaminants present in the water. Information on how to conduct water treatment is
available from water plants or water utilities as well as several companies and engineering consultants
who are experienced in this area.

Depending upon the coolant composition, the analysis values for the water should lie within the following
limits:

1.2.2 Fresh-water quality for coolant composition as under item 1.1.1 (passenger-cars and
commercial-vehicle engines)

Sum total of alkalis (water hardness): 0 to 3.6 mmol/l (0 up to 20° d)*

pH value at 20°C: 6.5 up 8.5

Chlorine ion content: max. 100 mg/l

Total chlorides and sulfates: max. 200 mg/l

1.2.3 Fresh-water quality for coolant composition as under item 1.1.2/1.1.3 (commercial-vehicle
engines)

Sum total of alkalis (water hardness): 0 to 2.7 mmol/l (0 up to 15° d)*

pH value at 20°C: 6.5 to 8.0

Chlorine ion content: max. 80 mg/l

Total chlorides and sulfates: max. 160 mg/l

If in doubt, contact DaimlerChrysler AG, department EP/MOR (operating fluids), C 405, D-70546
Stuttgart, Germany.

* Customary designations for water hardness in various countries: 1 mmol/l=5.6° d=10° f=7.02° e=100
mg/kg Ca CO.

3.

1° d (German degree =1° dGH)=1.78° (French degree)=1.25° e (English degree )=17.9 mg/kg Ca CO

3

(USA hardness).

1.3 Premixed coolant

Several providers have water with premixed coolant in their product range. Provided they are approved
(see below), they can also be used; the regulations relating to application, composition, change intervals,

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etc. of these coolant specifications also apply. It is imperative that the correct concentration (50/50) is
used in their application and, of course, further dilution is not permitted!

Approval status:

Coolants for all vehicle and engines (Basis 325.0) Sheet 326.0

Coolants for commercial vehicle and industrial engines (Basis 325.2) Sheet 326.2

Coolants for commercial vehicle and industrial engines (Basis 325.3) Sheet 326.3

The regulations for each respective Sheet 325.x are to be transferred correspondingly to Sheet
326.x.

At the time of compiling these regulations it is possible that not all the Sheets 326.x are represented with
approved products.

2. Coolant additives (General information)

Normally, coolant consists of water and anticorrosion/antifreeze agents. The anticorrosion/antifreeze
agents (ethylene glycol with corrosions inhibitors) in the cooling system have to fulfill, among other
things, the following functions:



to provide sufficient corrosion and cavitation protection for all cooling system components



freezing point depression (antifreeze)



increasing boiling point

For corrosion protection purposes the coolant

approx. 50 vol.-% Anticorrosion/antifreeze agents are added if the expected ambient temperatures do not
require an even higher concentration. This concentration (50 vol %) offers frost protection up to approx. -
37°C. A higher concentration is only necessary if the ambient temperatures are even lower.

Even with extremely low ambient temperatures, not more than 55 vol.-% anticorrosion/antifreeze agent
should be used, because at this level the maximum antifreeze protection is reached and a greater
concentration reduces the antifreeze protection again and decreases the heat dissipation (55 vol.-%
corresponds to antifreeze protection down to approx. -45°C).

Should these coolant regulations fail to be observed then corrosion and damage to the cooling
system are inevitable.

The admixture of anticorrosion/antifreeze agent serves to increase the boiling point. By raising the
pressure the boiling temperature can be increased yet further. Both physical relationships are put to use in
modern cooling systems - the maximum coolant temperature is raised, without increasing the danger of
boiling. In keeping with the higher temperature level the cooling performance is also greater. Only
approved products (Sheet 325.0/326.0 or 325.2 or 326.2, 325.3 or 326.3 as well as 312.0 or 311.0)

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provide reliable cooling system protection. In special cases (commercial-vehicle engines, no antifreeze
specification) coolant additives can be used that are primarily corrosion protection additives. In this case
item 2.3 is valid.

As an exception, if neither anticorrosion/antifreeze agent conforming to Sheet 325.0 nor coolant additives
without addition of antifreeze conforming to Sheet 312.0 are available, proceed according to point 2.4
(exception: OM 500 and OM 900). The systems described under items 2.2/2.3/2.4 are not compatible
with each other. It is recommended to mix the entire coolant quantity outside the engine.

2.1 Anticorrosion/antifreeze agent for passenger-car engines

Alongside the correct constitution of the cooling water (point 1.2.2), care must be taken to ensure that
only anticorrosion/antifreeze agents as approved for all engines in accordance with Sheet 325.0 are used.
These products serve to guarantee that, in particular, an effective protection against corrosion is provided
for all light-alloy parts in the cooling system and they are also specified for all passenger-car engines.

In order to ensure that the protection against corrosion is effective, the anticorrosion/antifreeze agent must
remain in the cooling system throughout the year - including when in tropical climates - and regardless of
the operating conditions. In countries with high outside temperatures this is also important in terms of
raising the boiling point.

In the event that these regulations are not observed the cooling system may suffer from damage by
corrosion. As a consequence of corrosion deposits there is a danger that ducts in the radiators (engine
overheating) and heat exchangers (poor heat output) get plugged up thus causing damage to the engine.

As a result of the optimizations we have carried out on the system of engine/coolant/cooling system, in
the majority of our newer passenger cars, a replacement of coolant is not necessary until reaching 15
operating years or 250,000 km (whichever comes first). This may not apply to some models; in these
cases the maintenance booklet will stipulate another regulation.

2.2 Anticorrosion/antifreeze agent for commercial-vehicle engines (normal case)

(not: BR 600, BR 100 and BR 200)

The coolant in commercial-vehicle engines is made up of both water and anticorrosion/antifreeze agent
(refer to item 1.1.1) and as such offers ideal protection against corrosion and cavitation.

All the approved products on the Sheets 325.2, 325.3 or 325.0 which are part of the Specifications for
Operating Fluids can be used to select an anticorrosion/antifreeze agent. However, it should be noted that
passenger vehicle engines built into commercial vehicles must be filled like passenger vehicles (e.g. OM
601 in T1), i.e. a product conforming to Sheet 325.0 and 326.0 must be used.

Products that are not listed in Sheets 325.0 and 326.0, or 325.2 and 326.2, or 325.3 and 326.3 are not
approved and are therefore not to be used under any circumstances.

Anticorrosion/antifreeze agents or coolants conforming to Sheet 325.3 or 326.3 may be used for

longer than other products due to their composition. The change interval is set at 5 years (refer to

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Overview Section 5). However, it should always be remembered that anticorrosion/antifreeze
agents or coolants conforming to Sheet 325.3 and 326.3 must not be mixed with those conforming to
Sheet 325.0 or 326.0 or 325.2 and 326.2.

2.3 Coolant additives for commercial-vehicle engines without antifreeze specifications (refer to item
1.1.2) (not: BR 600, BR 100 and BR 200)

In those application cases where no antifreeze is necessary, coolant for commercial-vehicle engines as
under item 1.1.2 can be mixed to suit. It is impossible to cite generalized mixing proportions because the
application concentrations of products included in Sheet 312.0 may be different. If the tolerances exceed
or fall below those given in Sheet 312.0, then appropriate adjustments must be made. The coolant's
boiling point is only insignificantly increased by these additives. The starting-off water underlies the
more stringent regulations as under point 1.2.3. The usage period for this coolant is shorter than usual (see
position 3). If it is necessary to refill, the same product must be used and at the same concentration level.
The blending of different products is not permitted as stated in Sheet 312.0.

2.4 Coolant regulations for commercial vehicle engines (exception, not for engines OM 500, OM
900, OM 457 and OM 460)

In the event that neither an approved anticorrosion/antifreeze agent is available, nor a coolant additive in
accordance with sheet 312.0 and if temperatures do not drop below freezing then it is possible in this
exceptional case to use a coolant refining agent to 1 vol % if it is approved in sheet 311.0 (soluble
corrosion protection oil). This will not raise the boiling point. The starting-off water itself underlies the
more stringent regulations as under point 1.2.3.

The period of usage for this coolant, which may only be used in exceptional circumstances, is shorter than
usual (refer to position 3).

Water that is too hard may impair the emulsion resistance, with the result that the emulsion

breaks down (oil separation) and the engine's water jackets are contaminated.

2.4.1 Applying water refining mixture

When carrying out a new filling (initial filling or filling after a cleansing operation) an emulsion of 1.0-
1.5 vol % should be used. When refilling, an emulsion of 0.5-1.0 vol % should be used. Concentrations
that are too high (>1.5 vol %) do not improve the corrosion protection capability and may exert a negative
influence on seals and hoses.

3. Monitoring coolant operation

It is very important to monitor the coolant constantly if the engine is to run trouble free.

The concentration level should be checked every six months.

The inspection should be conducted with suitable apparatus. If, when monitoring the concentration of the
coolant, it is determined that the concentration of anticorrosion/antifreeze agent has reached 40 vol.% or
less or an antifreeze protection of -28°C is no longer guaranteed, the concentration must be increased to

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