Renault Coupes/Sedans/Wagons 1975-1985 Repair Guide

Crankcase Ventilation System

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OPERATION



Carburetor Equipped Models


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Fig. Fig. 1 Common PCV system used on carbureted engines-LeCar shown; calibrated jet with 0.059 inch orifice (A) and flame arrestor (B)

The crankcase ventilation system is a closed system and consists of an oil separator (flame arrestor) and connecting hoses with two air flow restricting orifices. One 0.2165 inch orifice is located in the routing hose between the air cleaner assembly and the oil separator, while the second, a 0.067 inch (R-15, R-17, 0.059 inch) diameter orifice, is located in the routing hose between the oil separator and the intake manifold.

This duel circuit allows the crankcase fumes to be drawn into the intake manifold during periods of high engine vacuum and as the engine vacuum drops, such as during rapid acceleration, the crankcase fumes are then directed to the air cleaner assembly, to be drawn into the carburetor air stream and passed into the engine's combustion chamber, there to be burned with the air/fuel mixture.

Fuel Injected Models


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Fig. Fig. 2 PCV system used on the Alliance and Encore models

1975-80 VEHICLES

The crankcase ventilation system is the closed type. An oil separator (flame arrestor) is used in the valve rocker cover with a routing hose to the air intake, just upstream of the throttle plate. At this point, an orifice of 0.158 inch diameter is used to control the flow of crankcase fumes into the throttle plate chamber. A second hose is routed from a "T" on the throttle plate chamber, to the air cleaner assembly, where a second orifice with a 0.138 inch diameter is fitted. With this dual circuit, both the throttle plate chamber and the carburetor air cleaner air stream work jointly to control the crankcase emissions and to route them into the intake system for burning with the air fuel mixture. Later engine models have the oil separator moved from the valve rocker cover. The condensed oil returns to the crankcase through a special routing hose.

1981-85 VEHICLES

The crankcase ventilation system is of the closed type. The system has the crankcase vapors collected in the valve rocker arm cover and directed to an oil separator (flame arrestor). A double circuit is used from the separator, one routed to the upstream side of the throttle plate chamber, while the second circuit is routed to the downstream side of the throttle plate chamber. A connecting line from the fuel evaporative canister is used to purge the canister of fuel vapor fumes as the engine is operating. Three sized restrictors are used, upstream side 0.197 inch orifice, downstream side 0.067 inch orifice and a 0.079 inch orifice restrictor is used in the line from the canister to the air manifold.

SERVICE



The system must be inspected and cleaned at specific time and/or mileage increments which is normally every 6,000 or 12,000 miles or every 6 months or one year. The hoses must be inspected for cracks and deterioration, the restrictors must be cleaned and the orifices opened to their original diameters. The flame arrestor and/or vapor separator should be cleaned in an appropriate solvent, dried and reinstalled.

 
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