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- Oct 1, 2009
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- Vehicle Year
- 1995
- Make / Model
- Mazda
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Chapter one and six of the Haynes manual explain it. The PCV valve plugs into the rubber grommet on top of the oil separator. During idle, high vacuum closes the valve and prevents crankcase vapors from entering the intake manifold. This keeps the idle steady. There is a hose somewhere (probably into the valve cover) that puts post-air-filter air into the crankcase. Under unusual circumstances, when there is too much pressure from the crankcase, the PCV closes again, and the crankcase vapors are routed back to the post-air-filter area, where they join intake air for combustion. I'll quote Haynes, ch.6, section 8:
"
1. The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by scavenging crankcase vapors. It does this by circulating fresh air from the air cleaner through the crankcase, where it mixes with blow-by gases and is then rerouted through a PCF valve to the intake manifold.
2. The main components of the PCV system are the PCV valve, a fresh-air filtered inlet and the vacuum hoses connecting these two components with the engine and EECS system.
3. To maintain idle quality, the PCV valve restricts the flow when the intake manifold vacuum is high. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to flow back through the crankcase vent tube into the air cleaner to be consumed by normal combustion.
"
And from chapter one:
"
...The PCV valve on SOHC four-cylinder engines is mounted in the oil separator on the left side of the engine."
OK, me again. The oil separator is just forward of the oil filter, under all the intake stuff. Haynes doesn't mention any repair/replacement of the item, so I just soaked it, shook it, and drained it, quite a few times. Lots of hardened oil came out, probably a couple spoonfuls, little chips and bits. I blew through it to make sure it wasn't clogged, and it passed my air with no restriction at all. I shook my PCV, too, and looked at the hose, and they had a little oily residue, but the valve rattled, so I will re-use it after I re-install all the intake stuff. Maybe intake stuff will go on tomorrow. Cheers, guys. Hope this clears up the matter.
"
1. The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by scavenging crankcase vapors. It does this by circulating fresh air from the air cleaner through the crankcase, where it mixes with blow-by gases and is then rerouted through a PCF valve to the intake manifold.
2. The main components of the PCV system are the PCV valve, a fresh-air filtered inlet and the vacuum hoses connecting these two components with the engine and EECS system.
3. To maintain idle quality, the PCV valve restricts the flow when the intake manifold vacuum is high. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to flow back through the crankcase vent tube into the air cleaner to be consumed by normal combustion.
"
And from chapter one:
"
...The PCV valve on SOHC four-cylinder engines is mounted in the oil separator on the left side of the engine."
OK, me again. The oil separator is just forward of the oil filter, under all the intake stuff. Haynes doesn't mention any repair/replacement of the item, so I just soaked it, shook it, and drained it, quite a few times. Lots of hardened oil came out, probably a couple spoonfuls, little chips and bits. I blew through it to make sure it wasn't clogged, and it passed my air with no restriction at all. I shook my PCV, too, and looked at the hose, and they had a little oily residue, but the valve rattled, so I will re-use it after I re-install all the intake stuff. Maybe intake stuff will go on tomorrow. Cheers, guys. Hope this clears up the matter.
