Toyota Cressida/Corona/Crown/MarkII 1970-1982 Repair Guide

Crankcase Ventilation System

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OPERATION





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Fig. Fig. 1 PCV system air flow-22R engine



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Fig. Fig. 2 PCV system air flow-5M-E engine



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Fig. Fig. 3 The PCV valve functions differently according to engine operating conditions



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Fig. Fig. 4 The PCV valve seats into a grommet located in the valve cover 1. PCV valve 2. Grommet 3. Ventilation hose

A positive crankcase ventilation (PCV) system is used on all Toyotas sold in the United States. Blow-by gases are routed from the crankcase to the carburetor, where they are combined with the fuel/air mixture and burned during combustion.

A valve (PCV) is used in the line to prevent the gases in the crankcase from being ignited in case of a backfire. The amount of blow-by gases entering the mixture is also regulated by the PCV Valve, which is spring-loaded and has a variable orifice.

On Toyotas, the valve is either mounted on the valve cover or in the line which runs from the intake manifold to the crankcase.

The valve should be replaced at the following intervals:



1970-71 models-12,000mi/12mo
 
1972-74 models-24,000mi/24mo
 
1975-77 models-25,000mi/24mo
 
1978-82 models-30,000mi/24mo
 
1980-82 Calif.-69,000mi/48mo
 

REMOVAL & INSTALLATION



Remove the PCV valve from the cylinder head cover or from the manifold-to-crankcase hose. Check the attaching hoses for cracks or clogs. Install a new PCV valve into the hoses, or reinstall in the cylinder head cover.

TESTING





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Fig. Fig. 5 The arrows indicate the hose inspection points on the PCV system



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Fig. Fig. 6 When testing the PCV valve, blow air into the cylinder head side and check for good flow



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Fig. Fig. 7 Air should pass with difficulty when blown through the intake side

Check the PCV system hoses and connections, to ensure that there are no leaks, then replace or tighten, as necessary.

To check the valve, remove it and blow through both of its ends. When blowing from the side which goes toward the intake manifold, very little air should pass through. When blowing from the crankcase (valve cover) side, air should pass through freely.

Replace the valve with a new one, if the valve fails to function as outlined.

Do not attempt to clean or adjust the valve. Replace it with a new one.

 
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