Question about a poppet valve?

[KCLOST]

I've seen several topics about this, and I understand the principle of its existence. But I have some unanswered questions....<br />First off, I'm refering to the valve on my 1986 Mercury 175hp..<br /><br />It has the egg shaped cover (not the cover shaped like the number 8)...<br /><br />Anyway, I clipped a loop on the spring about a year ago just for the hell of it, to see if I could bring down my WOT temp readings (which at the time I thought were concerning, it didn't help by the way)... I also replaced the gaskets, grommet, diapram, cleaned the cover and divider place, etc....<br /><br />This week I decided to open it up again and inspect... At that time I went ahead and cleaned the plate and cover again, put in a new grommet, and pulled the spring with the clipped loop and put in a new one...<br /><br />After running it on the muffs, I noticed that water was spurting out of the outer cover drain hole... So I pulled it again and made sure the diaphram was seated properly and retested... Same thing happened. Water spurts out at idle rpms (anywhere above 800)...<br /><br />So at this point I'm confused.... Sure water is getting around the diapram, but that water has to come from the block which has to go through the poppet valve. And in my experience, that poppet valve shouldn't open above 15psi... At idle, I see about 10-12psi on the guage. <br />So I pull the valve again and decide to reinstall the spring with the clipped loop... Guess what! The spurting goes away, and doesn't appear even up to 2000 rpms... This is with a weaker spring, that should allow the valve to open at lower pressures...<br /><br />So my question... Should any amount of water go through the valve at any rpm, or only above 2500-3000 as I thought? And is this just a diapram seating poorly (if that is the case) causing the leak? And why would the design of the valve/spring allow it to be installed under tension so the diaphram is pushed outward at all times (making it hard to keep a good seal during installation, I think the clipped spring helped me install it better)... But I still wonder why I would see water at all at 1000rpm or less, as the poppet was seated into the grommet and under good tension with the new spring...<br /><br />Any thoughts, and sorry for the long post...

 

[KCLOST]

Re: Question about a poppet valve?

 

[dingbat]

Re: Question about a poppet valve?

You have it backwards. The poppet acts as a pressure relief valve and will only opens when the pressure is above XX PSI. When the pressure is below XX PSI (low RPM) the valve remains closed and forces the water to circulates through the block and into the heads where is dumped out the thermostats. When the pressure exceeds XX (high RPM) the valve opens and allows the excess coolant to bi-pass the cooling system and get dumped directly to discharge. If my water pump is in good condition I can sit at the dock and rev the motor up and actually watch the pressure bounce around as the poopet pens and closes. <br /><br />Your shortening of the spring actually reduced the flow of coolant thorough the motor.

 

[KCLOST]

Re: Question about a poppet valve?

dingbat, I understand that... And I know how it is suppost to work. <br /><br />But with the "non-shortened" spring, why would I see water spurting out of the outer cover plate, if I'm only running at Idle? The valve is open at lease somewhat for that water to exit...