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1998 LS AWD Forest Green metallic
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I always thought that small hole was to allow trapped air to pass through, so as to not allow an air pocket.
Some thermostats even had a small 'wiggler' device in that hole, to help keep it from getting plugged up.
Either way, it is designed to be there, and I agree it is not causing your cold running problem.
Some thermostats have a second diaphram at the base. I think Mmusicman posted a photo of one recently.
I do not know which style our vans use. The manual does not show anything but a general drawing. I have never had a need to look at, or to replace one.
Rod J
Issaquah, WA
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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MotoRad thermostats make them with a "jiggle pin" which is loose (moves up/down in hole).
It's a bleeder there to reduce thermal shock of cold/hot mix when themostat first opens.
It may also help pass trapped air when closed to.

I normally use this model.. but if not I drill my own hole.

What is important is that correct thermostat is used with dual valves (with newer blocks).
When closed to radiator, the lower valve is open... circulating warmed coolant within the engine block, improving warming time.
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This thread is about "freezing to death"...
You think you got it bad... be sure to see my post about "FALLING IGUANAS"
 

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That's just a bleed hole. It lets the engine warm up just that much faster - old AC Delco thermostats actually came with that hole drilled. It doesn't cause a cold condition, it causes your engine to warm up just that much faster.

That's not the cause of your trouble.

The thermostat might have failed, which would be the cause of your trouble.
That may be true in some circumstances, but my truck wouldn't get past the 100 degree line, Ever. Now that I have one without a hole in it, it heats up to 195 like it's supposed to in a fraction of the time. But good info either way.:)
 

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That has nothing to do with the bleed hole. The thermostat failed, you replaced it. Period.
 

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a grill cover won't really help with the engine getting to temp. it helps the motor hold heat in the block and bay which helps hold heat in the cab. as you have already said the thermostat controls the coolant temp.
raise the front end with a jack so that you can bleed any air from the system. it's possible the heater core is blocked. Best to connect a hose to the outlet and force some city water pressure through it to clean it out.
The factory valves for the heater core are not great either so I'm told. if you want more heat people do a mod with plumbing valve so that you get more flow to the heater core. I'm going to do that at some point on my van cause I'm here in Ontario too and my heat works okay but not as great as other vehicles I've used.
as a last note, my vans heat really starts to blast when I got my foot to the floor.

As I left dillons grocery store. I heard a grating metal noise. My safari went down about a foot it seemed. I was 4 blocks from home. Drove gently home.
Broken torsion bar. One little nub end is stuck in that cylinder rod housing connected to the key. Towards the back of van. Someone said to just cut the cylinder housing off. And it all comes apart there.
Any thoughts?

Here's some pictures.
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The third picture some say to cut that rod tube housing off?
 

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That may be true in some circumstances, but my truck wouldn't get past the 100 degree line, Ever. Now that I have one without a hole in it, it heats up to 195 like it's supposed to in a fraction of the time. But good info either way.:)
hole is to aid in removing air when bleeding coolant. often guys who have cooling issues down south drill the hole to help them bleed the system properly otherwise when bleeding your constantly waiting on the thermostat to open and close to bleed it properly. if it fixed your van it's cause it wasn't bleed properly and had air in the system. when I had low coolant from a leaky water pump my temp gauge went from 40 - 100 - 40 like crazy (C not F).
hole that small shouldn't have an effect on cooling or heat
Also my van used to take 20minutes of driving to heat up but thermostat fixed that. test the thermostat
 
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