thermostat

[Corik]

Hey guys, I've had the suspicion that my thermostat was bad.
I've was told that one way you can test is to hold the top radiator hose and if it warms up slowly rather than suddenly then the thermostat is bad/stuck open.
I did this and it reacted this way.
I bought a Motorcraft thermostat, and after some cussing and time I got the old thermostat out...but it isn't stuck open.
I even tested it in a pot of hot water. it opens fine and closes again.

The only thing i noticed is that there is a little hole on the side. The Motorcraft has the same hole; however, it has a little bead there like it wouldn't let as much through.

here is a pic of the old...

so should I just put the old one back on?

 

[Common Cents]

Those holes are "bleed holes" which prevent air from being trapped on one side of the thermostat and allow a very minimal flow through the system, even when the thermostat is closed. They are completely normal.

The little tab is sometimes added to reduce the flow through the bleed hole. If I get a new thermostat with one of those tabs, I routinely cut off that tab to leave the hole open on any thermostat I install.

To answer your actual question, I'd probably keep the new one installed. Unless you have an accurate thermometer, you don't know what temperature the old one was opening at. They also don't last forever. Since you've done all the work, might as well get the maximum life out of the job.

 

[Corik]

I think it says on it 195, may as well i guess

 

[Roadrunner777]

I'd leave it in. Technically, the little hole should be installed at the top 12'oclock position. The little hole does indeed prevent steam from building up behind it, and reduces the volcanic reaction when bleeding air out of the system. I did not know this before I replaced mine, and so the hole is down at 3'oclock, but I doubt it makes much of a difference.