On some Thermostats that have the small vent hole, they also have a rivet or some sort of metal 'widget' in the hole. Why? Why put the hole there then partly block it? Also, I've noticed if I drill even just one small vent hole, say 3/32" in a thermostat in a Chevy, when it's really cold, 10deg or less, the engine seems to take a lot longer to warm up than when there is no vent hole. Anybody else notice that?
The hole is there to prevent a sudden surge of coolant and the engine cooling off too much. By allowing a small amount to go by the engine will heat up at a constant rate. People have been doing this forever, but some engine manufacturers including Kubota are acting like this is a new idea Sent from my HTC One M9 using The H.A.M.B. mobile app
Perhaps the rivet is a check valve? or it might let air through quickly, but not coolant? Yeah, it does not take much coolant flow to keep an engine cool at really cold outside temps.
I thought the hole was there to vent air when you're filling it initially? At any rate, I drilled a 3/32 hole, and then put a cotter pin in it to restrict it....why.....I really don't know.
The wiggler lets air thru upon filling. Once it sees water pressure the wiggler restricts the flow thru the hole. I thought I'd be smart and drill a tiny hole my wife's Thermostat on here late model. It's a pain to bleed and burp the air on it. Well that solved the bleed and burp issue so well I did it to my nieces car too. They both soon thru a trouble code that the engine was taking too long to warm up. SOOO , it's 100 proof that hole and the coolant flow thru it makes it take longer to warm up.
Ha! Damn computers... But wow that's amazing proof! I wondered if it was my imagination. Hard to believe such a small hole could make the difference. I better use a rivet or a nail instead of a cotter pin, so they will seal off.
Well, 1. Forgot about the wiggler. 2. It's not for a car so the auto parts people (Advance) are clueless. I took in the water neck to get a (thermostat) gasket, and the guy put the casting number on the neck in the computer....idiot. And that was after I told him it was John Deere. 3. Already got the one without it, and drilled the hole. I could ask at NAPA, I didn't install this one yet.
I've always used a 1/16 inch bit and never had a problem. Air goes through a 1/16 hole easily but not as much water will go through. Even if it takes a few minutes for the air to go through, it isn't a problem. A smaller hole would work too but 1/16 is the smallest bit in most sets.
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