Air whoosh behind intake plenum??
Thread Starter
|
Member
Joined: Dec 2021
Posts: 112
Likes: 6
From: Philadelphia
Air whoosh behind intake plenum??
So I've been convinced that I've had a vacuum leak even though I'm at like 21 in Hg at idle because my truck idles high all the time no matter what but that's a a whole different thing than what this post is for. I just replaced the PCV valve and the hose for it because I was convinced that was my vacuum leak. When I'm seeing their idling with my head in the engine bay and I quick hit the throttle I hear like a quick whoosh right down where the PCV valve is and I'm wondering if this normal for it because it's happening the second the engine loses vacuum to the throttle? Do you all hear this noise on yours too or is it something funky with mine and maybe I should re-replace the PCV valve?
PCV Valve has a weighted valve inside it, what you feel moving if you shake a PCV Valve
When vacuum is high this weighted valve is pulled UP closing off the upper end connected to intake
When vacuum drops, so does the weighted valve, allowing intake vacuum to suck out "Blowby" from crankcase/valve covers
So yes, the "whoosh" would be normal when vacuum dropped in intake
All piston engines have "Blowby", its the exhaust gases that blow by the piston and rings and into the crankcase when a cylinder fires
In the bad ol' days there was a vent on upper oil pan or low block that vented Blowby out into the air
It also dripped oil
Only place in an engine that gets hot enough to vaporize oil is in the combustion chamber, so the Blowby gases(exhaust) are hot enough to vaporize some of the oil coating rings, piston and cylinder walls, this is where the oil vapor in an engine comes from, most of it condenses inside the crank case
PCV(positive crankcase Ventilation) was added to engines in the early 1960s
It has a PCV Valve hooked to the intake, and a Breather hose hooked to other valve cover on V engines
This pulls out the exhaust gases from blowby and burns it in the engine
As an engine gets older blowby increases so oil vapor increases(also cheap oil increases oil vapor), so intake can get an oil coating on the inside
Many install a Catch Can on the PCV valve hose to try and condense oil vapor faster so it doesn't get into the intake
When vacuum is high this weighted valve is pulled UP closing off the upper end connected to intake
When vacuum drops, so does the weighted valve, allowing intake vacuum to suck out "Blowby" from crankcase/valve covers
So yes, the "whoosh" would be normal when vacuum dropped in intake
All piston engines have "Blowby", its the exhaust gases that blow by the piston and rings and into the crankcase when a cylinder fires
In the bad ol' days there was a vent on upper oil pan or low block that vented Blowby out into the air
It also dripped oil
Only place in an engine that gets hot enough to vaporize oil is in the combustion chamber, so the Blowby gases(exhaust) are hot enough to vaporize some of the oil coating rings, piston and cylinder walls, this is where the oil vapor in an engine comes from, most of it condenses inside the crank case
PCV(positive crankcase Ventilation) was added to engines in the early 1960s
It has a PCV Valve hooked to the intake, and a Breather hose hooked to other valve cover on V engines
This pulls out the exhaust gases from blowby and burns it in the engine
As an engine gets older blowby increases so oil vapor increases(also cheap oil increases oil vapor), so intake can get an oil coating on the inside
Many install a Catch Can on the PCV valve hose to try and condense oil vapor faster so it doesn't get into the intake
Thread
Thread Starter
Forum
Replies
Last Post
