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A condenser (air conditioning radiator) of a multi-flow type is installed in front of the radiator of the engine cooling system
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If traces of oil leakage through the crankshaft seals are found, then first you need to check if the crankcase ventilation system is clogged and if the hoses of this system are pinched
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We remove the heater elements for replacement or repair.
Removing and installing the control unit was discussed in the article - Removing the Renault Duster heater control unit.