Why doesn't my new thermostat have this?

[ThreeQuarter]

The Motorcraft (made in Germany?!?) thermostat that I removed from my motor has a check valve near the shoulder. Maybe it's because I'm a GM guy, but I've never seen one of these before. I understand this is a pressure bleeder of sorts? So my question is: Why does my Stant HD thermostat I installed not have this?

 

[Lt.Jim]

Some do some don't. I've seen two different versions of the stant thermostats one with and one w/o the bleeder valve. Most people who get the ones without the bleeder just drill a 1/8" hole that works just as well. Don't know why the differance?

 

[ThreeQuarter]

Interesting. At the time of this photo, the Stant had already been installed. Is the bleeder critical? What can I expect different without it?

BTW, I'm glad to see the t-stat replacement did what I was trying to accomplish. Before, with the Motorcraft t-stat, my needle moved between the two white ticks on the LH side of the gauge. Now it holds to the "N" all the time, which is what most Fords that I've driven have done.

 

[BrooklynBay]

The main thing is to match the temperature range. Some thermostats are designed to get stuck in the open position when they jam. I've had a couple of thermostats jam in the closed position, and had to break them. It always happens while driving on the highway far away from home without any place to get a replacement!

 

[ThreeQuarter]

BB, as far as temp range, they were the same (old one was a 91C and new one is a 195). The old one must've been opening early, because it wasn't stuck open when I took it out.

But my question is: Why would this engine need a bleeder when all the others I've ever worked on didn't?

 

[Maniak]

As I understand it.. That factory bleeder allows air to bleed through to help get out air bubbles. Most of the thermostats I've seen in for the explorer have it.

The way the water flows, it pushes the hole closed (some have a nice bearing like yours, others are just a pieces of brass)..

In our hot southern Az summers I run a 180F thermostat with a 1/8" hole drilled in it.. That way there is always water flowing and it does seem to help keep the explorer cooler (if I run that thermostat in the winter the temp won't get over 165F).

~Mark

 

[gijoecam]

Indeed, the bleeder hole needs to be there to prevent air from being trapped at the top of the system. It's also essential that it be installed with the bleeder at the 12:00 position to maximize its effectiveness at preventing the air bubble from forming.

-Joe