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Old 04-20-2005, 10:25 PM
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Drill thermostat

Again w/ the dodge 2.2 questions.But I'm haveing a hell of a time fingering this out.
So far I've replaced the thermostat(#4 or 5 now),put a new radiator cap(16lb stock),found the electric fan motor bad and replaced it,and replaced the coolant sensor.And filled the system w/ 50/50 mix.I evan fill the system w/ the nose up in the air(recomended for 2.2 by a dodge site)to purge the air outta the water box(as they call it) were the stat sits.
The engine isn't boiling over now.But while I was filling the radiator the car ran up to 3/4 on the gauge befor the fan kicked on.Is this right??
The normal temp is 1/4 on gauge.
I took it out right after this and it ran at normal temp the whole time.
Now when I took it out after it had cooled completely down.It would run the gauge up to almost full after 3mi of driving then pop down to normal and stay there.This is what it has done since I've owned it(3yrs)and everytime I replace the stat it cures it for 3mo then starts again(2 others told me they have the same problem).Cept this time its still doing it w/ a new stat.
Think if I drill 2 holes in the base of the stat,it will alow enough water to pass through so it don't have to overheat befor the stat opens??

(if ya read my headgasket post about a week ago I think the foam I saw was just setament from burnt coolant.The motor has no water in oil,Steam out exhuast,discolored coolant(oil) and also isn't bubbling in the coolant now,other than when its starting to boil form the stat problem)

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Last edited by 78 monte; 04-20-2005 at 10:34 PM.
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Old 04-20-2005, 10:49 PM
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Stock engines are built with bypasses that heat the thermostat with a constant slip stream of coolant so it will open properly. I think you are on the right track in that it sounds like the passage in your engine is plugged. Does the engine run @ design low temp once the 'stat finally opens? If so that is the problem. If it stays at the high reading all the time with the 'stat, the bypass isn't the problem and you need to look elsewhere. While you can drill a couple of 1/8" holes in the rim of the 'stat and achieve the necessary bypass function, that isn't very elegant. Should be a last resort. Better approach would be to find out why the bypass passage isn't functioning and fix that.
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Old 04-21-2005, 12:46 AM
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I don't think drilling it will help cure your problem. Do you know what temp these events are happening or do you just have a gauge with no numbers?

The thermosat is going to open at the same temp. no matter if you have holes drilled in it or not. Small 1/8 inch holes will not flow enough to keep the car from reaching the magic temp at which the thermostat will open. Drilling the holes do help removed trapped air and if that's your problem it will help. I doubt that is your problem because once the system is purged (the first time the stat opens) all the "trapped" air should be gone.

I am not familiar with that particular engine or cooling system but, do they make or will a fast acting thermostat fit? If so that is the way to go. I have had some of the "typical" low cost stats do that to me (drilling didn't help, I tried it). They just don't open on time and can cause heat cycling. I have never had a problem with a high flow fast acting stat. Check to see if Robert Shaw, Mr Gasket, Milidon, makes one that will fit your application. they are about $10 an it is money well spent.

Royce
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Old 04-21-2005, 02:07 AM
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Most import engines use a vented thermostat (an opening at the top-install to face top-that allows air pockets to be released. Sounds like you have an air pocket behind the thermostat. Have you tried a genuine MOPAR thermostat?

The thermostat has to be in there to properly regulate the coolant flow. The thermostat opening/closing will actually vary with continuing coolant temperatue change. So it has to be a quality piece.
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Old 04-21-2005, 02:35 AM
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I use one from Robertshaw but Summit does´nt list them anymore, this one from Milodon is the same piece.They open in the direction of water flow and not against it http://store.summitracing.com/defaul....asp&x=33&y=11 Part number MIL-16400.
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Old 04-21-2005, 08:13 AM
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Willys,yes once the stat opens I could drive it cross country and it would not overheat again.
camaroman,its a stock gauge w/ just three lines and a red spot,no numbers.
I'll look into a Genuine Mopar stat.I've got a Stant in there now.
I just got home from work.I work approx 2.5-3mi from home.I started it cold at work and drove it and by the time I got home the gauge was pegged.I poped the hood and the upper hose is ice cold.
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Old 04-21-2005, 08:49 AM
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What year and model is this DODGE?
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Old 04-21-2005, 08:55 AM
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Quote:
Originally Posted by camaroman7d
I don't think drilling it will help cure your problem. Do you know what temp these events are happening or do you just have a gauge with no numbers?

The thermosat is going to open at the same temp. no matter if you have holes drilled in it or not. Small 1/8 inch holes will not flow enough to keep the car from reaching the magic temp at which the thermostat will open. Drilling the holes do help removed trapped air and if that's your problem it will help. I doubt that is your problem because once the system is purged (the first time the stat opens) all the "trapped" air should be gone.

I am not familiar with that particular engine or cooling system but, do they make or will a fast acting thermostat fit? If so that is the way to go. I have had some of the "typical" low cost stats do that to me (drilling didn't help, I tried it). They just don't open on time and can cause heat cycling. I have never had a problem with a high flow fast acting stat. Check to see if Robert Shaw, Mr Gasket, Milidon, makes one that will fit your application. they are about $10 an it is money well spent.

Royce
You are correct as long as the factory bypass is operational. When the thermo is closed, the water is trapped in the engine and is heated up. The factory designs in a small slip stream (For example Old Pontiac V8 engines have an obvious hose that goes from the water pump to the intake manifold - that is their bypass. Most others us a hidden internal passage). This passage directs a small stream of heating water past the expanding element of the thermo so when the temperature reaches thermo rating, it begins to open and full flow occurs. The engine temperature never exceeds the thermo setting if this is operational and the rest of the system is in good shape. However, when that passage is plugged as in 78 Monte's case, the thermo is isolated from the heating water in the block so it will stay closed until it is heated by conduction from the heating engine which takes a lot longer, all the while the water is getting hotter than the thermo setting. That cold upper hose when the engine is very hot is a dead giveaway of this very phenomenon. The thermostat is seeing that cold hose temperature and until heat is conducted to it from the overheating engien, it will stay closed. Once the thermo cracks open, hot water flows past it and it will function properly until the engine cools down, then it must be conductively heated to open again. Has nothing to do with air in the system. Drilling the 1/8" holes in the thermo is a substitute for the passage, circulating the heating water past the thermo and it will work as designed. Another interim solution is to turn on the car heater which circulates the water past the thermo and it will open OK. The best solution is to clean out that bypass passage.
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Old 04-21-2005, 09:31 AM
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Willys I see what you're saying but you are acting as if the thermostat is "isolated" from the hot engine water. That is not the case. It is sitting in the engine water so once the water is above the opening temp, it should open. Even if the water just above the stat is cooler. That would throw it off by a few degrees (delay the opening) but should not make the gauge peg before it opens. Could be a combination of things here. Very slow acting thermostat and a plugged bypass. This would make sense. Drilling the holes only cost him a few minutes of his time and it is worth a shot. If it works great, if not the real problem needs to be fixed. They didn't come from the factory with holes drilled in them and they worked.

Royce
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Old 04-21-2005, 09:58 AM
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Thermotats are sitting in engine coolant yes, but the water behind the 'stat is stagnent, or without movement. Without moving coolant to carry heat to the 'stat copper thermal device, you have to wait untill the heat moves through the water to reach the 'stat. Convection. This can take awhile. Heat moves through water at roughly 1/2 per minute, depending on the density and impurity's tempeture ect..., You see, it has to move through the heads, throught intake jackets, some will go through the metal of the intake but most will go through water for it's less restrictive for convection. If you measure the distance you get several inches. All the while the water near the sender keeps rising.
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Old 04-21-2005, 09:59 AM
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Holes aren't a fix, but a good crutch. And free
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Old 04-21-2005, 10:08 AM
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KULTULZ,its a 1994 Dodge Shadow.
Well I drilled two holes but I went a bit bigger than 1/8".
I took it for a drive and the temp gauige never came off cold.I let it run in the drive way and it started climbing and reached half on the gauge(1/4 is noramal).Then I took it back out and as soon as air went through the radiator the temp dropped to just above cold.
So I think w/ smaller holes(1/8" like recomended)I'll run at normal temp.Its just I have the overheating if I sit in traffic??
I called a dealer and they told me to flush the heater core??I think they just wanted me off the phone.
I saw online that your sposed to purge air outta the water box through a plug on the top of it.I guess this is the highest point in the system and also the stat sits in the front of it.Think there still could be an air bubble at the top of it??Seems unlikely.

Last edited by 78 monte; 04-21-2005 at 10:24 AM.
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Old 04-21-2005, 11:02 AM
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Quote:
Originally Posted by camaroman7d
Willys I see what you're saying but you are acting as if the thermostat is "isolated" from the hot engine water. That is not the case. It is sitting in the engine water so once the water is above the opening temp, it should open. Even if the water just above the stat is cooler. That would throw it off by a few degrees (delay the opening) but should not make the gauge peg before it opens. Could be a combination of things here. Very slow acting thermostat and a plugged bypass. This would make sense. Drilling the holes only cost him a few minutes of his time and it is worth a shot. If it works great, if not the real problem needs to be fixed. They didn't come from the factory with holes drilled in them and they worked.

Royce
Trust me, it works just like I described! Has nothing to do with air in the system or type of thermostat in place. Sure the thermostat is sitting in the engine water but the water around the exhaust valve is getting a WHOLE lot hotter sooner than the idle water around the thermostat sensing bulb at the front of the intake manifold. Water temoperature gauges are usually in the head where the water is getting hottest fastest and it reads accordingly, while a thermostat w/o circulation of the hot water past it is ignorant of what is going on. Eventually, there is enough gravity circulation of hot water and conduction through the iron (aluminum) that reaches the thermostat and it responds. If the water isn't overtly circulated past the thermostat, it takes longer time to get it going and you will ALWAYS get that scary peak in water temp just before the thermostat opens. Very scary but doesn't last long enough to do any harm. Happens with ANY thermostat- quick opening or otherwise. That's why they install the bypass at the factory. I first ran into this on my 235 in-line 6 in my '53 Chevy pickup. Bypass was inoperative and every morning my engine water temp would spike to +240F then instantly drop to 180F and stay there the rest of the day. I got around it for a couple of years by turning on the heater, but finally got off my duff and got the bypass working and no problems since. A couple of holes in the thermostat flange doesn't affect how it works but does allow the heating water to reach it and get it to operate as designed. Works fine but just not the BEST fix!

Last edited by willys36@aol.com; 04-21-2005 at 11:10 AM.
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Old 04-21-2005, 11:36 AM
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I am not familiar with your engine.One thing I have seen on a few honda,s is the vanes on the water pump will be rusted to the point of there isn,t much left on them and the water will not circulate well.The test for this that I have found is,the car will overheat with the fans running setting still.Then when you bring the rpm,s up the temp will start to drop(starts to circulate better).Just something I have run across on rare occasion's.
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Old 04-21-2005, 01:20 PM
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Shadow's are notorious for guages that read wrong. And tachs that fail. The pre printed circuit boards are to blame.
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