Drilling Bleed holes in a Thermostat - Chevelle Tech
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  #1  
Old Jan 13th, 10, 8:54 AM
Dave427 Dave427 is offline
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Default Drilling Bleed holes in a Thermostat

I posted this in heating & cooling with no responses.
Some guys drill bleed holes in thermostats to help with air locks etc. What size of hole or holes would you drill?

Dave
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  #2  
Old Jan 13th, 10, 9:04 AM
69-CHVL 69-CHVL is offline
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Default Re: Drilling Bleed holes in a Thermostat

Dave I drilled a couple of 1/16 holes, and the motor took forever to warm-up! Had to replace it. FWIW, the Moroso one I purchased has one hole formed into it. Dont get a Mr. Gasket one whatever you do.
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Old Jan 13th, 10, 9:05 AM
Highway Star Highway Star is offline
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Default Re: Drilling Bleed holes in a Thermostat

I just drilled a 1/8" hole in mine a few weeks ago.
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Old Jan 13th, 10, 9:50 AM
Scotch Scotch is offline
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Default Re: Drilling Bleed holes in a Thermostat

I drilled four 1/16 inch holes in mine. Runs real cool all the time. Fine by me. Hot oil and cool water make for a good running engine.
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  #5  
Old Jan 13th, 10, 10:22 AM
david bull david bull is offline
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Default Re: Drilling Bleed holes in a Thermostat

Over the years,I've seen thermostats with a floater type plastic check ball that dropped down with gravity and floated up when fluid level reached the thermostat.Most of these were used on imports,but possibly are available for domestic.Early mercedes & hondas used a bleeder(much like a brake bleeder)to release air from the cooling system.Many of these engines were destroyed by unknowingly not bleeding the system.At any rate,a small bleeder hole in the thermostat is probably a good ideal.Another trick, if the thermostat is out or being replaced, is to put a small piece of a toothpick in the thermostat.When the engine reaches operating temp the thermostat opens &releases it.DBULL
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  #6  
Old Jan 13th, 10, 10:42 AM
Beaux Beaux is offline
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Default Re: Drilling Bleed holes in a Thermostat

Quote:
Originally Posted by david bull View Post
.Another trick, if the thermostat is out or being replaced, is to put a small piece of a toothpick in the thermostat.When the engine reaches operating temp the thermostat opens &releases it.DBULL
Is this so that after a few flushes you can flush your rad and have a bunch of kindling for winter fires? Can you elaborate a bit? I am a rookie and not seeing the benefit.
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Old Jan 13th, 10, 10:50 AM
69-CHVL 69-CHVL is offline
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Default Re: Drilling Bleed holes in a Thermostat

Quote:
Originally Posted by david bull View Post
Over the years,I've seen thermostats with a floater type plastic check ball that dropped down with gravity and floated up when fluid level reached the thermostat.Most of these were used on imports,but possibly are available for domestic.Early mercedes & hondas used a bleeder(much like a brake bleeder)to release air from the cooling system.Many of these engines were destroyed by unknowingly not bleeding the system.At any rate,a small bleeder hole in the thermostat is probably a good ideal.Another trick, if the thermostat is out or being replaced, is to put a small piece of a toothpick in the thermostat.When the engine reaches operating temp the thermostat opens &releases it.DBULL
Pretty interesting tip, although I cant say I ever had an issue bleeding my system. I know there's certain motors that are a complete b!tch trying to get the air out.

I would imagine that the tooth pick will disolve after a short period of time. If it even made it to the waterpump, it would be chopped into pulp pretty fast, dissolving even quicker.
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  #8  
Old Jan 13th, 10, 11:09 AM
david bull david bull is offline
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Default Re: Drilling Bleed holes in a Thermostat

The ideal is to use maybe a 1/8" piece,not the whole toothpick.It's so small it will probably never be seen again.This actually works.DBULL
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  #9  
Old Jan 13th, 10, 11:49 AM
Tom Mobley Tom Mobley is offline
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Default Re: Drilling Bleed holes in a Thermostat

I drill 2 1/8" holes in t-stats.
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  #10  
Old Jan 13th, 10, 12:35 PM
Calculated Risk Calculated Risk is offline
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Default Re: Drilling Bleed holes in a Thermostat

I go with one 1/8 hole. Just enough to get the air to bleed past. But so little not much coolant flows past when the stat is closed. If a single 1/8 inch hole prevents a V8 gas engine from warming up then i'm stumped. My chevelle has 8.4:1 compression and i have no t-stat, only a 3/4 inch restricter, it warms up pretty fast even on a cold day.
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  #11  
Old Jan 13th, 10, 1:05 PM
1966_L78 1966_L78 is offline
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Default Re: Drilling Bleed holes in a Thermostat

I usually drill 3 or 4 1/8" holes near the perimeter. I figure it not only bleeds easier initially, but it adds a little more flow...
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  #12  
Old Jan 13th, 10, 1:18 PM
elsolo elsolo is offline
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Default Re: Drilling Bleed holes in a Thermostat

I always drill two 1/8" holes in thermostats.
I can't say I have done lots of scientific testing on various hole sizes, flow, and cooling; but I never have a problem bleeding the air out, or running at a temp other than what the thermostat is rated at.
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  #13  
Old Jan 13th, 10, 1:23 PM
Elcoman Elcoman is offline
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Default Re: Drilling Bleed holes in a Thermostat

one very tiny hole should be plenty.
I used my smallest bit to drill a hole in the t-stat. If you want the t-stat to do its job, then one small hole is enough.
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  #14  
Old Jan 13th, 10, 1:43 PM
Schurkey Schurkey is online now
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Default Re: Drilling Bleed holes in a Thermostat

A hole in the thermostat does NOTHING useful once the engine has been run long enough to open the thermostat. The moment the thermostat opens, any air in the engine burps into the radiator and is seen as a "low coolant level". Unless the engine is run VERY low on coolant, no air can re-enter the engine while it's running; no air is "created" in the engine coolant passages; and if you're blowing compression/exhaust into the cooling passages, a hole in the thermostat is an inappropriate "fix".

The PRIMARY reasons to use a thermostat is to keep the minimum operating temperature of the engine high enough; and get it there quickly. Adding extra hole(s) defeats that purpose.

Why not take five minutes during the initial warm-up to top off the coolant? I'd spend nearly that much time digging up the drill and bits, restraining the thermostat in a vice, and popping the hole in it.

Putting holes in thermostats is a total waste of time and effort.
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  #15  
Old Jan 13th, 10, 2:21 PM
Dave427 Dave427 is offline
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Default Re: Drilling Bleed holes in a Thermostat

I am not doing this to increase flow , just once in a while my car gets an air bubble while warming up initially. I thought of drilling a small hole to burp it if needed,
There is something I read a while back about Dart blocks needed a drilled thermostat.

Dave
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