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Discussion Starter · #1 ·
I tested the thermostat that I had in the engine that I just removed- It is from autozone and it is a couple of years old.
The brand is Robertshaw-
It was in the center of a pot of water with 2 candy thermometers and a digital thermometer-
Results-open at 180-NO
Open at 190-NO
When-it started to open at 195 but it was not fully open until the water boiled which was around 207 on the thermometers.

#2- A brand new t-stat from autozone that I have never installed- autozone brand.
Did NOT open at 180- it started to open at 192 and fully opened at 200.

#3- The current thermostat that I took out of my car this morning.
Brand- Mr. Gasket
Opened at 180- NOOOOOOO
190? NO
195? barely
200? not yet
205? Yeah...finally....

More info-
All of these thermostats are 180*
Each t-stat got a fresh pot of water and sat in the water from start to finish
When I say they start to open I mean that they only open about 1/16"
When I say fully open I mean the spring is fully compressed.
These were tested in the center of the pot- not above the heat-the thermometers were right next to the t-stats.

So......could this possibly be the problem?
If so...should I run the engine without a thermostat to check the results?
Should I switch to a 160* t-stat and hope that it will open at 180?

Thanks everyone- all of your info has been very helpful..
 

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Running without a T-stat will result in overheating at highway speeds as the water will flow too fast for the radiator to get it cool . Several manufacturers sell a plate that you can install instead of a T-stat that has somewhere around a 5/8# hole for the water to be restricted with .
Id go buy some T-stats and test them until you fiond a good one .
 

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Discussion Starter · #3 ·
So a 180 thermostat should open right around 175-185, right? ::

I have checked three and they are all bad...
 

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In a pressurized system, a proper antifreeze mix wont boil anywhere near 212.......
 

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Discussion Starter · #5 ·
Please explain what you are trying to say...

I am using 1 part antifreeze to 2 parts water.

I used 50/50 before with no luck...

Are you saying the thermostats are good?
 

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So if we have the SoCal party at your place are you serving boiled thermostats as an appetizer? :: fd
 

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A 180 t/s should open at 180 +/- a few degrees. Stick with the 180 and keep trying till you get one that's right. It's not totally uncommon for a new one not to work correctly. I also test a new one before instllation.
Dave
 

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Most have a tolerance . If it's a 180 is should be open by 180-190 degrees .
Id lean more towards 185 max to full open . Most times they begin to open before the 180 mark but don't reach full open till 180 or slightly after . All the T-stat is for is regulating your engine temp . If the engine runs cold it will burn more fuel and make less power . If it runs hot , you will get more power until parts start dragging from over-heat swelling .
T-stats don't care about water , anti-freeze , etc. it's just by the temp surrounding the "sensor" of the stat . When the radiator cap is on and working correctly it causes the coolant system to become pressurized . The pressure is a result of the expansion of the coolant during the warm-up cycle of the engine . Added pressure will increase the boiling point of most fluids , water and anti-freeze included . Anti-freeze raises the waters natural boing point and lowers the waters freezing point . Both properties are now used on a engine , freeze protection and the extra added boil protection .
If water boils it becomes steam and no longer has the abillity to cool any internal engine components .
I can't remember the ratio but I think a less mixture (like 25 anti to 75 water) raises the boiling point more than 50/50 but I may be wrong as it's been years since tech school :)
If you want to test your stat theory , take a pair of cutters and cut the arms off one of your bad stats and "gut it out" so that all is left is the outer metal ring , with it's restrictor hole . It won't be small enough to restrict flow for normal use but should allow you the testing your looking for . The engine of course should take a lot longer to warm up .
 

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Discussion Starter · #10 ·
Haha... ::

Just think...If we all meet here I dont have to fix this problem! My car will just sit in the garage... :p
 

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I have doubts about the concept that in a closed system (like that of an automobile), you need to run a thermostat (or restrictor) in order to "slow" the water down for the radiator to work. I'd be interested in the science behind this claim. IMO, either the radiator has the capacity/efficiency to cool the engine or it doesn't. If it can cool the engine, then you may need a thermostat to to prevent over-cooling. If the radiator doesn't have the capacity/efficiency to cool the engine, then the engine will overheat regardless of whether a thermostat/restrictor is present or not. As long as the circulating pump transfers the cooling liquid between the radiator and engine at some minimum rate, the other factors will prevail. A deficiency in the capacity/efficiency of the radiator will result in overheating either at low speed/idle conditions (not enough air flow), or at high speed (not enough capacity), or all conditions (simply an inadequate cooling system).
 

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My 71 Firebird with a built 400 used to always jump to 210-220 when I was stuck in city traffic (with a new big 3 row radiator) so I took the thermostat out about 15 years and have never had any problems. Runs about 180-185 for normal highway cruising, when in city traffic rarely goes above 200 but have never had a problem when on the open road. It was my weekend cruiser I took up to the lake every weekend (when it was not raining) for 16 years which was a 70 mile drive each way if I went straight to the cabin and always ran perfect after I took out the thermostat.
 

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Funny you should mention this test procedure, this is basically what I did in my first job as a test tech. I had a dial indicator in a vat of coolant and we'd heat it at somthing like 1 degree per minute, had to record STO (start to open) and FO (Fully Open). We were checking vendors quality control. Don't remember results though, it was 25 years ago.
 

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No man; Bernie has got it exactly right. Think of it this way: if water was circulated through a cooling system (motor/radiator) really fast, but the radiator was encased in plastic so no air could flow through and essentially no heat could radiate, you think the water would get as hot as the motor? You betcha. The cooling system is a filled, closed, pressurized loop, so the coolant effectively maintains "contact" w/ the heat of the motor all the time (convective heating). The issue isn't transferring the heat of the motor into the water; that's unavoidable. The trick is transferring the heat out of the water, via the radiator. Like Bernie requested, a little more science to back some of these claims would be useful. :p

Jim
 

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There is a mathematical formula to determine the transferability of heat from the coolant to the metal of the radiator. That is the reason that a 4 row is more efficient at cooling than a 2 row radiator. There is more surface area of metal in contact with the same given amount of coolant. The equation is dynamic, in that the time of contact, as well as contact area, determines transferability. Think about it. It's like putting your finger in a flame. The heat transfer to your finger increases the longer your finger is in the flame. With a radiator, it is the same principal but in reverse.

I run a diesel, so cooling is important. I run straight distilled water with a bottle of water wetter. Adding the water wetter dropped the temp 20 degrees. According to the label on the bottle, water wetter has some type of composition to promote the heat transferability of the coolant to the radiator. It worked.
 

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Not sure which post you were replying to, but I agree with your point. As to Bernie's point re adequate radiator capacity: certainly, as you point out, a radiator's capacity to cool will be rated at some specified flow of coolant, and also w/ some specific coolant composition (water/antifreeze, water/water wetter, etc). So, to maybe re-phrase a little, given a radiator w/ adequate capacity (which I think is really the crux of the matter), and within reasonable limits of coolant flow (which I would assert your typical water pump produces), the notion of coolant moving through the engine block too quickly to cool seems mis-guided. If coolant were really zipping through that quick, it would seem the first limit you would exceed would be the optimal flow rate required by the radiator to do it's thing, not the optimal rate through the block to suck up heat into the coolant.

As to the use of restrictors as supporting the no-thermostat-overheating theories - from what I know, restrictors serve to sustain optimal pressure/flow within a cooling system designed for the restriction of a thermostat but run w/o one; so a restrictor is used in place of a thermostat to sustain pressure and smooth flow, and thereby minimize cavitation and subsequent hot spots.

And that's what I think . . .
 
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