Pcv Valve

[GJM85]

Unfortunately I broke the grommet that holds the PCV stem in tappet cover. I bought a mini air filter and fitted in on instead but without the manifold vacuuming the crankcase fumes out oil pressure went to shit and smoke started coming out of every orifice of the engine. She's not broken... yet. It only starts after about 1 minute of running so there'll be no more running until I can track down that grommet.

 

Does anyone know if its possible to purchase the grommets or does anyone have a few to spare?

 

Cheers.

Edited January 29, 2011 by GJM85

[ae824ate]

You should be able to track down one at repco etc relativly cheap. Have you looked around?

[GJM85]

You should be able to track down one at repco etc relativly cheap. Have you looked around?

 

Not yet. It only happened late this afternoon so haven't had a chance. Just hoping I could get a head start. Repco sounds like a good place... :y:

[towe001]

http://www.eziautoparts.com.au/pcv-grommet-pcg-04.html

 

Have bought a few things through them. The way they do their invoice and payment system is a bit goofy but their pretty good.

[19914afc]

Just go to a toyota parts dealership, there just a generic grommet only a couple of dollars.

[Trev]

Without it your engine should be venting, sounds like a blockage in the rocker cover, take the oil cap off and see if it improves.

[altezzaclub]

Doen't sound likely... I've run mine without the PCV vale in place without a problem, and while I can see that you get fumes coming out it shouldn't affect the oil pressure or the starting.

 

Broken ring?? Piston?? something that is pouring compression down into the sump...

[Twinky]

While we are on this subject. I am doing a draw through setup with my supercharger, would I have to weld on a valve onto the piping before the supercharger to relocate the pcv valve?

Or could i run a breather on it?

[Trev]

Doen't sound likely... I've run mine without the PCV vale in place without a problem, and while I can see that you get fumes coming out it shouldn't affect the oil pressure or the starting.

 

My point exactly, I would dare say that the rocker cover has a blockage and is causing the engine to pressurise but with vacuum attached it is sucking the excess out.

 

While we are on this subject. I am doing a draw through setup with my supercharger, would I have to weld on a valve onto the piping before the supercharger to relocate the pcv valve?

Or could i run a breather on it?

 

PCV is basically a one way valve, it should be fine.

[altezzaclub]

would I have to weld on a valve onto the piping before the supercharger to relocate the pcv valve?

 

It won't work, you can't run one.

 

The PCV is a bullet inside a casing with a spring in front of it. When you accelerate hard and manifold vacuum drops the spring pushes the bullet away from its seat and air is sucked from the tappet cover to the inlet manifold and burned. When you lift off and decelerate or idle the strong vacuum in the inlet system sucks the bullet onto its seat against the spring and closes the flow of air off.

 

You would have air being pushed into the tappet cover by the supercharger at boost if you run it to the inlet pipe. If you run it to the air cleaner it will never be under suction and will just act as a vent from the crankcase, which is what the crankcase inlet does via its tube to the air cleaner when you idle.

 

If your rings are worn then when the high vacuum closes the PCV the air in the crankcase flows the oppostite direction through the tappet cover vent into the air cleaner. You just need that vent working normally and close the PCV off. Pressurised air from the crankcase will go through that tube, & out the dipstick hole and out through the crankshaft seals...

[Trev]

It won't work, you can't run one.

 

The PCV is a bullet inside a casing with a spring in front of it. When you accelerate hard and manifold vacuum drops the spring pushes the bullet away from its seat and air is sucked from the tappet cover to the inlet manifold and burned. When you lift off and decelerate or idle the strong vacuum in the inlet system sucks the bullet onto its seat against the spring and closes the flow of air off.

 

You would have air being pushed into the tappet cover by the supercharger at boost if you run it to the inlet pipe. If you run it to the air cleaner it will never be under suction and will just act as a vent from the crankcase, which is what the crankcase inlet does via its tube to the air cleaner when you idle.

 

If your rings are worn then when the high vacuum closes the PCV the air in the crankcase flows the oppostite direction through the tappet cover vent into the air cleaner. You just need that vent working normally and close the PCV off. Pressurised air from the crankcase will go through that tube, & out the dipstick hole and out through the crankshaft seals...

 

You sure about this?

 

When there is no vacuum the PCV is in the closed position, it opens under vacuum therefore if you have boost it will force the PCV closed and then will open once you create vacuum by lifting off.

 

The spring holds enough energy on the piston to keep it sealed.

[altezzaclub]

When there is no vacuum the PCV is in the closed position, it opens under vacuum

 

no no ... the PCV is to clear the crankcase under it's most dirty condition, full throttle when the maximum compression is forced down past the rings. So PCV valves open at LOW manifold vacuums. (wide open throttle)

 

When you are cruising, or rolling down a hill with throttle off or idling at the lights the motor has very little by-pass as its not working hard, and under those high-vacuum conditions the PCV valve shuts. Otherwise it would leak far too much dirty air into the idling motor and upset their emissions again.

 

I'm fairly confident I have it right, but if you know it works otherwise let me know.

 

You will also lose your brake booster under boost, but that doesn't matter as you shouldn't be braking then!

[Twinky]

Actually I just realized that I'll be able to connect is via that jigg that sits underr the carbie when I move it to the other side of the engine bay.

Basically my concern was that that pipe was usually connected to the bottom of the carbie mount and air was sucked into the manifold. Obviously when supercharging the motor

instead of being sucked through the charged air would work against the valve. Being a draw through setup the carbie runs under vaccume rather than pressure.

So when I mount the carbie I just connect it on that same jigg under the carbie.

 

A quick scetch of what I am thinking.

 

 

Tell me if you don't think it will work

[Trev]

Couldn't be bothered to write something up so I did a wiki search.

 

The PCV valve connects the crankcase to the intake manifold from a location more-or-less opposite the breather connection. Typical locations include the opposite valve cover that the breather tube connects to on a V engine. A typical location is the valve cover(s), although some engines place the valve in locations far from the valve cover. The valve is simple, but actually performs a complicated control function. An internal restrictor (generally a cone or ball) is held in "normal" (engine off, zero vacuum) position with a light spring, exposing the full size of the PCV opening to the intake manifold. With the engine running, the tapered end of the cone is drawn towards the opening in the PCV valve by manifold vacuum, restricting the opening proportionate to the level of engine vacuum vs. spring tension. At idle, the intake manifold vacuum is near maximum. It is at this time the least amount of blow by is actually occurring, so the PCV valve provides the largest amount of (but not complete) restriction. As engine load increases, vacuum on the valve decreases proportionally and blow by increases proportionally. With a lower level of vacuum, the spring returns the cone to the "open" position to allow more air flow. At full throttle, vacuum is much reduced, down to between 1.5 and 3" Hg. At this point the PCV valve is nearly useless, and most combustion gases escape via the "breather tube" where they are then drawn in to the engine's intake manifold anyway.

Pcv valve.jpg

 

Should the intake manifold's pressure be higher than that of the crankcase (which can happen in a turbocharged engine, or under certain conditions, such as an intake backfire), the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again. In many cases PCV valves were only used for a few years, the function being taken over by a port on constant depression carburetors such as the SU. This has no moving parts or diaphragm to jam, block or rip like many PCV valves. It also doesn't have a 'one-way' function but the lack of it was never a problem in intake backfire.

[altezzaclub]

the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again.

 

Ah, Ok- That's what I thought, but it seals with the other end of the bullet when under pressure, so under boost it is closed off.

 

Anyway, what you say is correct Twinky, that inlet pipe after the carb and before the S/C is under vacuum the same as an NA inlet manifold, so that will work as usual.