Overheating Issue....
Racer
Joined: Feb 2013
Posts: 477
Likes: 15
From: Long Beach Ca
The Non Thermal design will spin the fan blade 50% of engine speed year round. Unfortunately it works far better in winter driving and far poorer in Summer Driving. Just the opposite of what you need. These non thermal designs are only used because they are cheap to buy and fit in the space needed. They waste fuel all winter by engaging the fan when not needed and don't work when needed in the summer. Not a good choice ever but again, they fit the space and they are cheap to buy. A Non-Thermal fan clutch looks just like most fan clutches but if you look at the face, the front facing the radiator there is not spring, just a stamped steel cover.
This was taken from Haydens web site.
"Non-thermal clutches operate based on the shaft speed of the water pump. At low and idling speeds, the clutch allows the fan blades to turn at almost a 1:1 ratio. At high speeds, the silicone fluid contained in the clutch loses its ability to transfer the energy from the shaft to the fan clutch body (and therefore the fan), and the fan is then allowed to almost free-wheel, removing its load from the engine"
Last edited by SS409; May 17, 2015 at 05:07 PM.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,145
Army
Well I won't agree that EVERYthing the GM engineers did was perfection.
The C1 clutch Z-bar single-shear point bushing is one example; the horribly sloppy fit of the C1 radiator shrouds are another. Inches of gap at some points; filling those areas with closed cell pipe insulation does wonders for cooling (along with the rubber seal kits for the radiator)...
The C1 clutch Z-bar single-shear point bushing is one example; the horribly sloppy fit of the C1 radiator shrouds are another. Inches of gap at some points; filling those areas with closed cell pipe insulation does wonders for cooling (along with the rubber seal kits for the radiator)...
Pro
Joined: Jun 2009
Posts: 592
Likes: 378
From: MA
I prefer the temp gauge when it is on the left of center... but is it more of a psychological issue than a critical problem? Is running at 210* during extended idle considered severe or was the engine and cooling system designed to meet those parameters? Here are two more 1965 GM service bulletins to illustrate these points:
Further GM information from 1965 discusses optimal cooling temps and the range of temps the system was designed to handle:
All these CorvetteForum suggestions/tips/articles are for the OP to consider.
Subject: Temperature Gauge Reading Too High (No. 250-TSB-DR)
Model and Year: 1965 Corvette
Source: Chevrolet Engineering Service Letter
Bulletin No: TNP #66-1
Section: Section XII - Electrical and Instruments
Date: 11-16-65
Several field reports have been received describing owner complaints of excessive temperature gauge readings.
Investigation has revealed some faulty gauges, however, it appears that the complaints may be largely psychological in nature. This may be because at normal operating temperatures the needle is positioned vertically or to the right of center and under extreme conditions the needle may be positioned physically close to the "Hot" mark although coolant temperature is within safe limits.
In production for 1966, the temperature gauge has been recalibrated so that at any given temperature the needle will be positioned further to the left, hence farther from the "Hot" mark. Under normal operating conditions the needle will be positioned to the left of center and extreme conditions will give a needle position at the center or right center of the gauge.
The gauge when available, may be used in the field as a replacement for the present gauge to alleviate owner complaints of high or erroneous gauge readings. Under no condition should any type of resistor be used to recalibrate either the new or present gauge.
The gauge cannot be used as a replacement on 1963 and 1964 Corvettes because of a styling change to the gauge face.
Model and Year: 1965 Corvette
Source: Chevrolet Engineering Service Letter
Bulletin No: TNP #66-1
Section: Section XII - Electrical and Instruments
Date: 11-16-65
Several field reports have been received describing owner complaints of excessive temperature gauge readings.
Investigation has revealed some faulty gauges, however, it appears that the complaints may be largely psychological in nature. This may be because at normal operating temperatures the needle is positioned vertically or to the right of center and under extreme conditions the needle may be positioned physically close to the "Hot" mark although coolant temperature is within safe limits.
In production for 1966, the temperature gauge has been recalibrated so that at any given temperature the needle will be positioned further to the left, hence farther from the "Hot" mark. Under normal operating conditions the needle will be positioned to the left of center and extreme conditions will give a needle position at the center or right center of the gauge.
The gauge when available, may be used in the field as a replacement for the present gauge to alleviate owner complaints of high or erroneous gauge readings. Under no condition should any type of resistor be used to recalibrate either the new or present gauge.
The gauge cannot be used as a replacement on 1963 and 1964 Corvettes because of a styling change to the gauge face.
Further GM information from 1965 discusses optimal cooling temps and the range of temps the system was designed to handle:
Subject: 1965 Corvette 350 H.P. Factory A/C Operating Temperatures
Model and Year: 1965 Corvette - 350 H.P Engine equipped with Factory A/C
Date: T.N. #7 - June 30, 1965
The following is an inquiry from Mr. Nick Pelster, Area Service Manager of the El Paso Zone, and my reply to his queries:
"I would like any available information on the approximate engine oil pressure and water temperature a '65 – 350 HP – air conditioned Corvette will run at at a given R.P.M.
I have an owner who has a Corvette who feels his unit should not run over 190° temperature with the air conditioning running. I have made every attempt to explain to this man that there is nothing wrong with his vehicle with no avail.
I have been told "Harrison" has a chart on the approximate satisfactory temperatures an engine should operate at."
+++++++++++++
Reference your note on the above subject received in this office May 6, 1965. We will deal, in this letter, primarily with the water temperature aspect of your owner's complaint.
Plain water in the Albuquerque Area will boil at approximately 200°F and if we used on our Corvettes a non-pressurized system, then the 180°F temperature might be marginal; but we use on all Corvettes a 13# pressure cap and this 13 lbs. adds approximately 39°F to the boiling point of water, or we safely say that in the Corvette the water will not actually boil until the temperature reaches 240°F. Some cars, specifically Cadillac, use 18# pressure caps. This, of course, would raise the boiling point of the pressurized coolant to around 255°F.
We use a pressure system on all of our vehicles due to the fact that the greater the temperature differential between the ambient (air through which the car is being driven) and the temperature of the coolant, the faster the radiator can dissipate heat, and the real criteria in any case is – does the system lose coolant? So, with the coolant not being able to boil under 240°F then there should be no loss of coolant. It is perfectly safe for all of our engines to operate at any temperature short of actual loss of coolant. They have been designed that way.
A radiator coolant temperature of only 190°F is at or near the temperature that it will be controlled by the thermostat. Actually, our thermostats are not completely opened until the coolant temperature reaches 212°F. Furthermore, we would say that any engine should operate at least 190°F to be in the low end of the proper operating temperature. This is necessary to help drive off products of combustion that get past the piston and into the crankcase because as you know, the temperature of the complete engine will be approximately that of the coolant.
We certainly wouldn't recommend that anything be done to this unit to lower the temperature and can assure you that if 190°F is as high as this job ever gets, the owner is certainly in no difficulty. In fact, his engine is running on the cool side.
We have run extensive tests in the Phoenix Area, specifically with Arizona Public Service Company, and we had no difficulty whatsoever with engine temperatures running in the 220°F and 230°F range. This was in no way detrimental to the engines, nor was there any loss of coolant experienced.
Model and Year: 1965 Corvette - 350 H.P Engine equipped with Factory A/C
Date: T.N. #7 - June 30, 1965
The following is an inquiry from Mr. Nick Pelster, Area Service Manager of the El Paso Zone, and my reply to his queries:
"I would like any available information on the approximate engine oil pressure and water temperature a '65 – 350 HP – air conditioned Corvette will run at at a given R.P.M.
I have an owner who has a Corvette who feels his unit should not run over 190° temperature with the air conditioning running. I have made every attempt to explain to this man that there is nothing wrong with his vehicle with no avail.
I have been told "Harrison" has a chart on the approximate satisfactory temperatures an engine should operate at."
+++++++++++++
Reference your note on the above subject received in this office May 6, 1965. We will deal, in this letter, primarily with the water temperature aspect of your owner's complaint.
Plain water in the Albuquerque Area will boil at approximately 200°F and if we used on our Corvettes a non-pressurized system, then the 180°F temperature might be marginal; but we use on all Corvettes a 13# pressure cap and this 13 lbs. adds approximately 39°F to the boiling point of water, or we safely say that in the Corvette the water will not actually boil until the temperature reaches 240°F. Some cars, specifically Cadillac, use 18# pressure caps. This, of course, would raise the boiling point of the pressurized coolant to around 255°F.
We use a pressure system on all of our vehicles due to the fact that the greater the temperature differential between the ambient (air through which the car is being driven) and the temperature of the coolant, the faster the radiator can dissipate heat, and the real criteria in any case is – does the system lose coolant? So, with the coolant not being able to boil under 240°F then there should be no loss of coolant. It is perfectly safe for all of our engines to operate at any temperature short of actual loss of coolant. They have been designed that way.
A radiator coolant temperature of only 190°F is at or near the temperature that it will be controlled by the thermostat. Actually, our thermostats are not completely opened until the coolant temperature reaches 212°F. Furthermore, we would say that any engine should operate at least 190°F to be in the low end of the proper operating temperature. This is necessary to help drive off products of combustion that get past the piston and into the crankcase because as you know, the temperature of the complete engine will be approximately that of the coolant.
We certainly wouldn't recommend that anything be done to this unit to lower the temperature and can assure you that if 190°F is as high as this job ever gets, the owner is certainly in no difficulty. In fact, his engine is running on the cool side.
We have run extensive tests in the Phoenix Area, specifically with Arizona Public Service Company, and we had no difficulty whatsoever with engine temperatures running in the 220°F and 230°F range. This was in no way detrimental to the engines, nor was there any loss of coolant experienced.
All these CorvetteForum suggestions/tips/articles are for the OP to consider.
Le Mans Master
Joined: Feb 2008
Posts: 6,463
Likes: 1,889
From: Folsom CA
Where are you getting your information from regarding non thermal clutches? I run one in my 327 here in so california. I do agree they are not efficient to use in winter driving conditions, but IMO, they do a better job of cooling in the hot summer months....
This was taken from Haydens web site.
"Non-thermal clutches operate based on the shaft speed of the water pump. At low and idling speeds, the clutch allows the fan blades to turn at almost a 1:1 ratio. At high speeds, the silicone fluid contained in the clutch loses its ability to transfer the energy from the shaft to the fan clutch body (and therefore the fan), and the fan is then allowed to almost free-wheel, removing its load from the engine"
This was taken from Haydens web site.
"Non-thermal clutches operate based on the shaft speed of the water pump. At low and idling speeds, the clutch allows the fan blades to turn at almost a 1:1 ratio. At high speeds, the silicone fluid contained in the clutch loses its ability to transfer the energy from the shaft to the fan clutch body (and therefore the fan), and the fan is then allowed to almost free-wheel, removing its load from the engine"
CRAP.I worked for Kool Klutch in the 80's leaving in 1991. We made Fan Clutches for the aftermarket and sold them in Kool Klutch brand and many other well known brands like 4 Seasons, Standard Motor Parts, Imperial, and many more. Hayden was our major competitor and Eaton produced most of the OEM product. OEM Producers need to do very large runs of part numbers while aftermarket players do short runs when they manufacture. We were a major player when this was big business selling Fan Clutches and Tranny coolers. We literally sold millions of Fan Clutches we made and sold all the types we talked about in the earlier post. I trust the engineering staff we had back then and I knew how they all performed and tested. Kool Klutch was sold off to Hayden when the market for these products declined as electric fans took over the Automotive OEM market. Today all Trucks still use a Thermal Fan Clutch for effectiveness. This is true for pickups and Big Rigs. They need more cooling than Electric fans can supply.
A Non Thermal Fan Clutch is priced 50% to 60% less than Thermal designs and they are sold to grab the low end of the market. They are not effective compared to a Thermal Fan Clutch Design.
The Non Thermal will work better when it is cold outside and your engine is cold and they will work far less well when it is hot outside and your engine is hot.
Non Thermals are supposed to spin your fan blade 50% the speed of the engine. In Fact this may happen when the temp is 70 degree's and your engine is cool, if it is 30 degrees and your engine is cool they will spin far faster nearing 90% of engine speed. When it is 105 outside and the Engine is running hot you may only get 30% of fan speed from the Non Thermal while a Thermal would be engaged and spinning the blade 80-90% of engine speed.
The Non Thermal will be engaged to its capacity year round wasting power and MPG for no gain.
Thermals are the way to go. Hope this helps.
Mark
Melting Slicks
Joined: Apr 2006
Posts: 2,331
Likes: 61
From: Sunnyvale CA
Steve
