engine runs too cool
Thread Starter
Instructor
Joined: Jul 2014
Posts: 163
Likes: 2
engine runs too cool
about a month or so ago my original radiator on my 72 ,350,4 speed started leaking. so I replaced the radiator with an aluminum one from champion. I also put in a new water pump , the stock cast iron type. I also changed all the hoses and clutch fan, belts etc. I had already been running a new fail safe 185 degree thermostat.... before the repairs my car would run in the 185/195 range. I have a temp gun that ive been checking it with because after the first test drive I thought my gauge had broken. not true. 20 mile run and the temp at the radiator, gauge and water pump was around 117/ 125. ok so heres the problem. if I crank it up and let it idle I can watch the choke open all the way. when I go down the road and its cool outside 50/60 degrees the choke will close because its cooling off too much. when I filled the radiator I put one gallon of anti freeze and the rest water. I live in east texas and it never really goes below 25/30 degrees here during the winter if that, plus my cars are all kept inside my shop so what did I do?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Your "fail safe" thermostat has failed in the OPEN position. The "fail safe" terminology doesn't mean that it will not fail; it means that when it fails, it will fail 'safe' (meaning that it can't fail in the CLOSED position and cause the engine to overheat).
Replace the stat with a standard Robert Shaw 180*F stat.
Replace the stat with a standard Robert Shaw 180*F stat.
Thread Starter
Instructor
Joined: Jul 2014
Posts: 163
Likes: 2
Your "fail safe" thermostat has failed in the OPEN position. The "fail safe" terminology doesn't mean that it will not fail; it means that when it fails, it will fail 'safe' (meaning that it can't fail in the CLOSED position and cause the engine to overheat).
Replace the stat with a standard Robert Shaw 180*F stat.
Replace the stat with a standard Robert Shaw 180*F stat.
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
Your "fail safe" thermostat has failed in the OPEN position. The "fail safe" terminology doesn't mean that it will not fail; it means that when it fails, it will fail 'safe' (meaning that it can't fail in the CLOSED position and cause the engine to overheat).
Replace the stat with a standard Robert Shaw 180*F stat.
Replace the stat with a standard Robert Shaw 180*F stat.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I think a 180* ts is a good compromise between a 160 or a 195. A 195 will heat the engine quicker but the engine will run hotter. A 160 and the engine will run cooler which may promote wear as the oil may not be at its optimum temperature.
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
I've experienced, here in the desert, a 160 or 185* t stat, once the motor gets hot, it's stays hot. The t stat doesn't stay closed long enough for the radiator to do it's job. Therefore, it stays open and the engine continues to get to a higher temp, or over heat, sometimes. If you have a 195* it will allow for exchange of the coolant from the engine to the radiator. The longer it can stay in the radiator, the longer the radiator has to do it's job. But, that's just what I've learned in my time. Results may vary, depending on location. I use this all the time though, so far, it's worked.
If the new car gauges read true, most people would freak out. New cars run "hot" by the old car standards. I bet my 6.6 diesel truck runs 230 or more....hahaha
If the new car gauges read true, most people would freak out. New cars run "hot" by the old car standards. I bet my 6.6 diesel truck runs 230 or more....hahaha
Tech Contributor
Joined: Jun 2004
Posts: 20,857
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I've experienced, here in the desert, a 160 or 185* t stat, once the motor gets hot, it's stays hot. The t stat doesn't stay closed long enough for the radiator to do it's job. Therefore, it stays open and the engine continues to get to a higher temp, or over heat, sometimes. If you have a 195* it will allow for exchange of the coolant from the engine to the radiator. The longer it can stay in the radiator, the longer the radiator has to do it's job. But, that's just what I've learned in my time. Results may vary, depending on location. I use this all the time though, so far, it's worked.
If the new car gauges read true, most people would freak out. New cars run "hot" by the old car standards. I bet my 6.6 diesel truck runs 230 or more....hahaha
If the new car gauges read true, most people would freak out. New cars run "hot" by the old car standards. I bet my 6.6 diesel truck runs 230 or more....hahaha
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Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
If you have a properly operating thermostat and cooling system...THERE IS NO WAY THE ENGINE COOLANT TEMP WILL BE LESS THAN THE THERMOSTAT RATING.
Put a 180 in it and move on
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
Dont care to discuss the physics. With a properly sized rad and good airflow, a 180 thermo wiil show the engine temps somewhat higher, but around 180.
To the OP, I was saying that a good thermo will not open till its rated temp...so it sounds like its stuck open. Also run 50/50 mix of coolant to stop corrosion.
There are a billion vehicles from every car company that will attest to this.
To the OP, I was saying that a good thermo will not open till its rated temp...so it sounds like its stuck open. Also run 50/50 mix of coolant to stop corrosion.
There are a billion vehicles from every car company that will attest to this.
Last edited by mikem350; Dec 1, 2016 at 04:03 PM.
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
You guys are right, with all the t stats that you use. I'm not here to argue, and I won't. I relay what has worked well for me.
If you have a 180* t stat, and if it's working properly, the engine won't get too far past 180* before it opens. And the same for a 195* t stat. So the engine getting a lot hotter with a higher t stat, isn't really relevant.
Use what you want, and I will too. I've been doing this for a very long time, as some others here have, and I don't have anything to prove. I just have experience to share, which is what I thought this forum was about. I know I'm not a well known person on this forum, but that doesn't mean I just started working on cars/Corvettes when I started on this forum (a common misconception with some here).
If you have a 180* t stat, and if it's working properly, the engine won't get too far past 180* before it opens. And the same for a 195* t stat. So the engine getting a lot hotter with a higher t stat, isn't really relevant.
Use what you want, and I will too. I've been doing this for a very long time, as some others here have, and I don't have anything to prove. I just have experience to share, which is what I thought this forum was about. I know I'm not a well known person on this forum, but that doesn't mean I just started working on cars/Corvettes when I started on this forum (a common misconception with some here).
Tech Contributor
Joined: Jun 2004
Posts: 20,857
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Dont care to discuss the physics. With a properly sized rad and good airflow, a 180 thermo wiil show the engine temps somewhat higher, but around 180.
To the OP, I was saying that a good thermo will not open till its rated temp...so it sounds like its stuck open. Also run 50/50 mix of coolant to stop corrosion.
There are a billion vehicles from every car company that will attest to this.
To the OP, I was saying that a good thermo will not open till its rated temp...so it sounds like its stuck open. Also run 50/50 mix of coolant to stop corrosion.
There are a billion vehicles from every car company that will attest to this.
Burning Brakes
Joined: Apr 2008
Posts: 1,222
Likes: 93
From: shelbyville West Michigan
quite the baffling group of posts here...t-stat stays open and overheats and must close to cool off? where do people come up with this stuff???
OP: I agree the t-stat may be stuck open.
I fail to see how it would run that cool in 60 deg. weather, however. how over-sized is the radiator?
how exactly are you measuring temp with an IR gun? are you somehow sampling the coolang? aiming it at the rad and waterpump is not going to give you an accurate reading.
as far as the choke, how do you know it is closing when you drive it? even at 117 degrees, the choke would stay open. sounds like you've got other issues.
OP: I agree the t-stat may be stuck open.
I fail to see how it would run that cool in 60 deg. weather, however. how over-sized is the radiator?
how exactly are you measuring temp with an IR gun? are you somehow sampling the coolang? aiming it at the rad and waterpump is not going to give you an accurate reading.
as far as the choke, how do you know it is closing when you drive it? even at 117 degrees, the choke would stay open. sounds like you've got other issues.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The T-stat does NOT set the operating temps of the cooling system; it merely sets the temp at which the stat will begin to open. The cooling system will continue to heat until it reaches ITS equalization temperature. You can run with no thermostat, and the final stabilized temps of the cooling system will be the same as if it had a 195*F stat in it. It will just take a lot longer to get there.
Chevy designed the SBC engine with a 180*F T-stat. 195*F stats were only required after emissions requirements were established. More hydrocarbons are burned off when the engine operating temps increase. But, of course, TOO hot is not good either. Car companies agreed to install 195*F stats...but they weren't happy about it. More engine problems (idle quality, warranty, etc), lower fuel mileage, and some other minor issues were negatives related to stat (and operating) temps higher than 195*F. So, from a "customer's" standpoint, a 180*F stat and stabilized operating temps not much above that level are what Chevy intended with the SBC engine.
Chevy designed the SBC engine with a 180*F T-stat. 195*F stats were only required after emissions requirements were established. More hydrocarbons are burned off when the engine operating temps increase. But, of course, TOO hot is not good either. Car companies agreed to install 195*F stats...but they weren't happy about it. More engine problems (idle quality, warranty, etc), lower fuel mileage, and some other minor issues were negatives related to stat (and operating) temps higher than 195*F. So, from a "customer's" standpoint, a 180*F stat and stabilized operating temps not much above that level are what Chevy intended with the SBC engine.
Last edited by 7T1vette; Dec 3, 2016 at 12:08 AM.
Race Director
Joined: Mar 2016
Posts: 14,331
Likes: 8,139
From: Napa Valley California
For no scientific reason, just rule of thumb since I was a kid and driving before my C3 was built.
Throw in a 180 degree thermostat and no worries.
Always seemed to work. Don't ask why, I can't tell you. It's just always worked fine.
Try a new 180 degree stat. If you don't like it, it only takes two bolts and a gasket to change it to a 195 or 160.
It does sound like the thermostat is failed to the open position.
Throw in a 180 degree thermostat and no worries.
Always seemed to work. Don't ask why, I can't tell you. It's just always worked fine.
Try a new 180 degree stat. If you don't like it, it only takes two bolts and a gasket to change it to a 195 or 160.
It does sound like the thermostat is failed to the open position.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
And the longer its in the engine, the increased chance of a hot spot.
Drifting
Joined: Feb 2005
Posts: 1,879
Likes: 38
From: Los Gatos CA
Been awhile since we've had a decent t-stat donnybrook... Cool!
Regarding coolant speed... You want the coolant to travel through the block and heads as quickly as possible to transfer the heat from the hotter engine to the cooler coolant. Transfer will continue to occur from the hotter to the cooler, until the coolant boils. Similarly, the radiator is a heat exchanger; heat exchange will occur up to the thermal efficiency of the radiator. Faster is better, up to a point where other factors come into play, like cavitation. Anyways, that's how I learned it...
Regarding coolant speed... You want the coolant to travel through the block and heads as quickly as possible to transfer the heat from the hotter engine to the cooler coolant. Transfer will continue to occur from the hotter to the cooler, until the coolant boils. Similarly, the radiator is a heat exchanger; heat exchange will occur up to the thermal efficiency of the radiator. Faster is better, up to a point where other factors come into play, like cavitation. Anyways, that's how I learned it...