Re: Explain the Poppit valve?
There was a great diagram of the water flow posted a while back that shows the flow through the various water jackets, heads, relief valve system, t-stats, and into the exhaust to exit. <br /><br />Maybe someone can find it and post it again...<br /><br />But basically the poppet valve works like this... At lower rpms, the main temperature control is the t-stats. At this point the water pressure is low and there is very little flow of water into the cylinder head water jackets... But once the temp. of the water that is at the top of the block near the t-stats reaches the 145F mark, the t-stats begin to open up and water flows through the head water jackets. You can see this happening with a water pressure guage, as my motor will run about 10psi at idle when cold, when it heats up and the t-stats open my water pressure will drop to about 5psi.<br /> This will continue up to around 2500-3000 rpms.. And I beilieve at this rpm you will see an increase in pressure to about 15-20 psi (I can't remember the exact measurement however). And the t-stats will still be open. At this point there is a constriction of water flow through the heads/t-stats/water jackets. More water is being supplied than can be exited, so what happens, the water absorbs heat, more heat, and can lead to an overheat condition. So at the right pressure level the poppet valve is pushed open and the water is able to escape, thus improving water flow through the entire system and allowing that extra flow necessary to cool the engine properly at higher rpms. As the poppet opens a little, the water doesn't actually go past the diaphram it just opens up a port that the water can go to and then into the exhaust. You have to remove the poppet to see it. It is right on the outward side of the grommet and carrier that the poppet slides into.<br /><br />If it is faulty, won't open, it can result in an overheat condition at higher rpms, the water is there but not enough flow to remove the heat absorbed by the water. If it will not close, it can result in an overheat condition at lower rpms as the water is dumped from the block and you lose the water needed to fully circulate the cooling system.<br /><br />You can also see when the poppet opens and closes with a water pressure guage. On my engine it seems to open and close around 2500-3000 rpms. This is what seems weird to me, When it opens the water pressure drops below the point/level that was needed to open it. The same goes when it closes, except in reverse.<br />Must be due to the weird design of the assembly...
