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#383998 - 07/23/09 04:48 AM Adding Weep Hole To Thermostat
YO7_A66 Offline
master

Registered: 01/20/03
Posts: 4646
Loc: Indiana
I asked this question on my "160 versus 180 thermostat" thread but I wanted to open up the question with more detail. I have attached a picture of a thermostat that has been drilled (apx 3/16" or so) and there is only one hole. I have read where some have drilled 2,3, or even 4 holes of 1/8" or 3/16" in diameter.
My first questions would be, how many is needed and how many is too many?
My understanding of the hole(s) is to allow the air to bypass the thermostat during the initial startup to "burp" the coolant system. But, once the air has been purged from the coolant system, what effect do these holes have on the cooling system?
It appears that coolant can pass thru these holes when the thermo is closed due to the pump pressure. Does this affect the cooling system? With our intakes designed with vertical thermo holes, is there enough coolant pressure to allow a steady stream of coolant to bypass the thermo with the weep hole(s) added?
I have already bought a Stant 195 thermo to swap out my 180 unit. Now I am just trying to understand the goods/bads of added the weep hole(s) before I start drilling.

Thanks


Attachments
5370170-thermo2.jpg (595 downloads)

_________________________
1970 YO7 A66 [Canadian Export] F8 Challenger 340(SL.P. 226/238@.050,270/288 dur,.489/.480" 112 deg., 9.7:1, 2.02's),RPM intake, QF SS-750 Annular DP, MSD Street Fire Ign., & TTI's. 727(built by Rick Allison) /Dynamic 9.5" 3800, TF-2, & A&A 5600rpm Hemi gov.)& 3:91's (235/60's & 255/60's).

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#383999 - 07/23/09 05:13 AM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
moper Offline
I Live Here

Registered: 02/03/03
Posts: 12491
Loc: Columbia, CT
The coolant should not flow until the stat opens. That's it's job is to regulate teh temperatue. It doesnt help cool. Is stops flow to keep things warm in a properly functioning and sized cooling system. I sometimes drill a 1/8" hole in them. But not all the time either. It only helps when filling. You should not have any air trapped in the heads or block after the system has been run and cycled. Especially if it's a coolant recovering type system where the coolant is drawn back into it while things cool down. If you had a series of holes it simply weakens the effect having a Tstat gives.
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Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.

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#384000 - 07/23/09 06:11 AM Re: Adding Weep Hole To Thermostat [Re: moper]
Magnum Offline
master

Registered: 01/24/03
Posts: 5292
Loc: Hamilton, Ontario Canada
Quote:

The coolant should not flow until the stat opens. That's it's job is to regulate teh temperatue. It doesnt help cool. Is stops flow to keep things warm in a properly functioning and sized cooling system. I sometimes drill a 1/8" hole in them. But not all the time either. It only helps when filling. You should not have any air trapped in the heads or block after the system has been run and cycled. Especially if it's a coolant recovering type system where the coolant is drawn back into it while things cool down. If you had a series of holes it simply weakens the effect having a Tstat gives.




Please sticky this response in the tech archives. This is the best answer on this subject yet.

I too used to drill one 1/8" hole without any "problems" but now that I understand cooling systems better. I prefer as is out of the box.

I will take quicker warm up, which you will have for the next 5 years or however long you leave your thermostats in for. Over letting coolant bleed through everytime you drive the car, when it's not supposed to. Just to rid a fresh system of some air bubbles one time.

Cheers moper
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69 Coronet, 97 Silverado, 99 Caravan, 93 Mustang

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#384001 - 07/23/09 06:40 AM Re: Adding Weep Hole To Thermostat [Re: Magnum]
scratchnfotraction Offline
I Live Here

Registered: 05/29/03
Posts: 14495
Loc: Florida
it just lets air out

cant hurt the cooling sytem,IMO

the intake bypass hose is there moving a larger amount of water bypassing the t stat

the water is going to take the path with the least restriction and the 1/8" hole is not going to be move any big amount of water past the stat

got to remember the bypass is there for a reason also,it lets the water recurculate in the block so the pump does not cavitate,this is how it warms up faster..heats 1/2 the water then the other 1/2 when it cycles..then its all at temp

some times you can see the stat cycle by the temp gauge...goes up some then drops..then climbs slowly back up..and drops again

when mine is doing this,the thermo clutch fan will lock up and you hear the fan blowing more air,as the warm water gets to the rad,as it cools, the fan backs off

this is idling for a good while in hot weather

I have seen them cavitate with the intake bypass blocked along with heater hose outlets with a stat installed

this was high rpms when the stat was not open and at temp..not good,this was the conclusion of the damaged t cover and pump.

removing the stat and using restrctors,fixed it,

but this is just my

away


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#384002 - 07/23/09 06:49 AM Re: Adding Weep Hole To Thermostat [Re: scratchnfotraction]
YO7_A66 Offline
master

Registered: 01/20/03
Posts: 4646
Loc: Indiana
Once an engine is up to the temp of the stat (lets say 195), does the stat always stay open from that point on or does it cycle open/closed?

Scratch,
""the intake bypass hose is there moving a larger amount of water bypassing the t stat""
Is this bypass hose for the newer cars?


Edited by YO7_A66 (07/23/09 06:50 AM)
_________________________
1970 YO7 A66 [Canadian Export] F8 Challenger 340(SL.P. 226/238@.050,270/288 dur,.489/.480" 112 deg., 9.7:1, 2.02's),RPM intake, QF SS-750 Annular DP, MSD Street Fire Ign., & TTI's. 727(built by Rick Allison) /Dynamic 9.5" 3800, TF-2, & A&A 5600rpm Hemi gov.)& 3:91's (235/60's & 255/60's).

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#384003 - 07/23/09 07:03 AM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
crlush Offline
super stock

Registered: 04/11/05
Posts: 777
Loc: Michigan
if your stat is opening at the proper temp and your engine is overheating, then you most likely have a problem somewhere else. if you think your stat is not opening at proper temp heat some water on stove with a temp gauge and drop it in and see what temp it opens up at.

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#384004 - 07/23/09 07:56 AM Re: Adding Weep Hole To Thermostat [Re: crlush]
Ronnman Offline
super stock

Registered: 01/20/03
Posts: 1146
Loc: Slidell, LA
Another thought on the 1/8" hole is it allows a small amount of flow, thus keeps the water passing the thermostat. This intern allows for a more accurate sensing of the water as opposed the the thermostat closed and blocking flow. I have been drilling one 1/8" hole in thermostats for years with nothing but positive results.
Ron

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#384005 - 07/23/09 08:03 AM Re: Adding Weep Hole To Thermostat [Re: crlush]
YO7_A66 Offline
master

Registered: 01/20/03
Posts: 4646
Loc: Indiana
CR,
I have no current cooling issues. I am doing some preventative maintenance by changing my thermostat that is 5 years old. So I am just doing some checking before I install my new unit.

Thanks to all responses so far.
_________________________
1970 YO7 A66 [Canadian Export] F8 Challenger 340(SL.P. 226/238@.050,270/288 dur,.489/.480" 112 deg., 9.7:1, 2.02's),RPM intake, QF SS-750 Annular DP, MSD Street Fire Ign., & TTI's. 727(built by Rick Allison) /Dynamic 9.5" 3800, TF-2, & A&A 5600rpm Hemi gov.)& 3:91's (235/60's & 255/60's).

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#384006 - 07/23/09 08:10 AM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
LAR_414 Offline
master

Registered: 01/20/03
Posts: 4567
Loc: ...gently down the stream
I just put a new Super Stat (STANT) 180 degree in my car yesterday. I drilled a small hole. I like to fill the system once, plus I like a little bit of flow past the T stat when trying to warm the car up, to lessen the chances of a hot spot back around the rear cyls. I have my bypass hose blocked off.
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Street car with a Stick - very low 11's, all small motor / cross ram, 15mpg pump gas.

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#384007 - 07/23/09 08:17 AM Re: Adding Weep Hole To Thermostat [Re: Ronnman]
RodStRace Offline
I Live Here

Registered: 09/21/05
Posts: 12303
Loc: Chino Valley
I didn't start drilling until I was a mechanic, and it was to allow faster filling. The hole pictured is too big, all it needs is a small one to let air pass. Many FWD and Asian car thermostats have a 'jiggle valve' built in.


With the amount of coolant in a typical V8 cooling system, I figure the amount bypassed is tolerable, and as the previous poster said, it allows the flow of heated coolant to open the 'stat a bit quicker. If you are taking your time and can let the system burp all the air out before running, you can install it without this mod. My is that if you are in a hurry and drill a small hole, you aren't going to cause any harm, provided it's properly located, you make sure all drill shavings are removed, and you don't damage the stat during the process.
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#384008 - 07/23/09 08:18 AM Re: Adding Weep Hole To Thermostat [Re: Ronnman]
MLR426 Offline
master

Registered: 08/17/05
Posts: 4723
Loc: ILL
Quote:

Another thought on the 1/8" hole is it allows a small amount of flow, thus keeps the water passing the thermostat. This intern allows for a more accurate sensing of the water as opposed the the thermostat closed and blocking flow. I have been drilling one 1/8" hole in thermostats for years with nothing but positive results.
Ron




Same here I agree.

logan426

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#384009 - 07/23/09 08:19 AM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
scratchnfotraction Offline
I Live Here

Registered: 05/29/03
Posts: 14495
Loc: Florida
no,the bypass has been on all small blocks from front of intake to wp nipple for yrs and even on the 92-up magnum 5.2/5.9 v-8s & 3.9 v-6

I need to go back and re-read

are you working on a BB?


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#384010 - 07/23/09 08:27 AM Re: Adding Weep Hole To Thermostat [Re: scratchnfotraction]
YO7_A66 Offline
master

Registered: 01/20/03
Posts: 4646
Loc: Indiana
Scratch,

340. After reviewing one of my engine pictures, now I think I know what you were referring too. The smaller hose that goes from below the t-stat housing to the pump. Thanks

Thanks again to all, this is very informative.


Attachments
5370432-Topatpump-1.jpg (199 downloads)



Edited by YO7_A66 (07/23/09 08:32 AM)
_________________________
1970 YO7 A66 [Canadian Export] F8 Challenger 340(SL.P. 226/238@.050,270/288 dur,.489/.480" 112 deg., 9.7:1, 2.02's),RPM intake, QF SS-750 Annular DP, MSD Street Fire Ign., & TTI's. 727(built by Rick Allison) /Dynamic 9.5" 3800, TF-2, & A&A 5600rpm Hemi gov.)& 3:91's (235/60's & 255/60's).

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#384011 - 07/23/09 09:41 AM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
moper Offline
I Live Here

Registered: 02/03/03
Posts: 12491
Loc: Columbia, CT
That's the one Dave... It always flows coolant and is not affected by the Tstat. And as to the earlier question... if the system is desgned right, the stat should open and stay at least partially open to maintain the temp. If it was overengineered it might close but you'd have to be runnign water less than you Tstat temp rating under it... so i dont thin that would happen.

LAR, the bypass blocked? Really? Never heard of that before. Heater lines sure, not the bypass.
_________________________
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.

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#384012 - 07/23/09 09:54 AM Re: Adding Weep Hole To Thermostat [Re: moper]
LAR_414 Offline
master

Registered: 01/20/03
Posts: 4567
Loc: ...gently down the stream
Yup,....I'm an oddball with an odd intake manifold.

I blocked the bypass hose but I do run the factory heater. So I am getting "bypass" through the heater core.

I still like the hole in the T-stat. Also makes for less "dumping" of cold colant into the block when the T-stat opens. Less shock


Attachments
5370592-Crossramsmallpic.jpg (165 downloads)



Edited by LAR_414 (07/23/09 09:55 AM)
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Street car with a Stick - very low 11's, all small motor / cross ram, 15mpg pump gas.

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#384013 - 07/23/09 10:17 AM Re: Adding Weep Hole To Thermostat [Re: LAR_414]
74Scamp Offline
pro stock

Registered: 01/20/03
Posts: 1488
Loc: New Mexico
This may be a dumb/stupid question: When initially filling a new engine, and start up, could you just leave the radiator cap off to allow any trapped air to escape once the coolant heated up enough and the Tstat opened and coolant started pumping through the radiator and hence, the whole system? Just wondering, cause this is what I did with my son's Mustang when the new engine was initially started. Took a while, but eventually, you could see the coolant flowing through the radiator with the cap off.

Dave

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#384014 - 07/23/09 01:56 PM Re: Adding Weep Hole To Thermostat [Re: 74Scamp]
scratchnfotraction Offline
I Live Here

Registered: 05/29/03
Posts: 14495
Loc: Florida
yes,you can do it that way,just be right there looking in the rad..as soon as it sucks it down add more coolant as it gets almost filled and your a little slow adding,the steam and air bubbles come blowing out as your trying to add more cold water..bad,IMO,can cause steam pockets and and hydroshock with cold coolant on very hot cast iron...cracks

yep thats the small bypass hose

LARS is correct running the heater hose with no bypass


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#384015 - 07/23/09 02:09 PM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
HealthServices Offline
Why would you even post that?

Registered: 12/08/07
Posts: 7759
Loc: So Cal
Having a weep hole is good. Just don't make it too big. Thermostats do not read the temperature of air pockets very good. And this one of the reasons why a motor with a head gasket leak will overheat. The thermostat will not open when there is a air pocket there.


If you have a high performance motor that is on the edge or use nitrous or a tired motor with a head gasket issue having a hole there will help.

The hole shown in the picture is more than enough. I would go smaller as it will affect how long it takes for a motor to warm up.

On a Honda I tried that size it was too big, and the motor never got warm. Tells you how efficient those things are.
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Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.

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#384016 - 07/23/09 02:26 PM Re: Adding Weep Hole To Thermostat [Re: YO7_A66]
Lefty Offline
master

Registered: 09/05/05
Posts: 6490
Loc: Santa Cruz, California
I've been OK with a single 1/8" weep hole for decades. A single 1/8" isn't going to affect the warm up imo. Trying to burp the system without the hole can be a pain in the...
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#384017 - 07/23/09 02:29 PM Re: Adding Weep Hole To Thermostat [Re: scratchnfotraction]
74Scamp Offline
pro stock

Registered: 01/20/03
Posts: 1488
Loc: New Mexico
I just wondered - that's the only way I knew how to do it. I always added coolant very very slowly and paid really close attention to things. I think I'll do this weep hole thing when (if?) I get my new 360 ready to run. Thanks very much.

Dave

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