| [GMCnet] It was the thermostat [message #272871] |
Mon, 02 March 2015 14:12  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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A short time ago I posted about an over cooling issue I was having with the new engine in the Clasco and how the plastic fan and fan clutch combo kept the fan clutch locked up when it should not be. We just returned from Eugene where Sharon had surgery on the lids around her eyes (successfully!) and this morning had time to instal a new Robert Shaw 195 thermostat to replace the 180 which went in with the engine R&R. That one change seemed to make all the symptoms go away. The standard duty fan clutch engaged at start up like it should, then quickly released after a mile or so. The water temp went to 195 and stayed there like it was painted on. I drove over the 1000 foot climb going south from where our building is located up to the tunnel near the top of the mountain that separates the Oregon from the California water sheds. The water temp moved only a tiny bit and never saw 200. The fan clutch never engaged. Coming back down was the same story. Water temp sat right
at 195 and the fan clutch and plastic fan behaved as they should. No belt squeaking.
When I measured the 180 thermostat it appeared to open early (down in the high 160 to low 170 range) and was fully open by 185 and fully closed again about 165. This same standard duty fan clutch and plastic fan combination with that thermostat locked on and never did sound like it fully released. So, all I can surmise at this point is that the combo of the aluminum radiator, plastic fan and a early opening thermostat kept the air temp coming through the radiator so low that the fan clutch never did properly distribute the torque fluid and kept the fan engaged when it shouldn't. Hence, I recommend not using a 180 with this combination.
The standard duty fan clutch is supposed to run the fan at 20% to 30% when disengaged and 60 to 70% when engaged. From this short experiment it seems like the plastic fan flows enough air even at 20 to 30% of crank speed to keep the engine heat well modulated. I will report more when the temperatures get into the 90s and low 100s if there is any change. The standard duty fan clutch is supposed to be for fans with a 1 1/2" pitch where our original steel fan and the plastic fan are both 2 1/4" pitch which would suggest the heavy duty fan clutch (designed for 2 1/2" pitch fans, 25-35% off, 70-90% on) might be a closer match so I will keep an eye on things through the spring and into summer. Thanks for all your constructive comments and suggestions.
Jerry
Jerry & Sharon Work
Kerby, OR
http://jerrywork.com
78 Royale
77/94 Clasco
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] It was the thermostat [message #272894 is a reply to message #272871] |
Mon, 02 March 2015 19:28  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I like the 195 as well. The temp is more stable as the delta T to the outside air is larger so a proper working stat can modulate the temp at the set point i'm doubting the reason for the fan clutch engagement with the cold stat was the startup fluid redistribution as even in sub zero, GM clutches redist and then turn "off" after a block or so of driving.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] It was the thermostat [message #272906 is a reply to message #272871] |
Mon, 02 March 2015 22:05 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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What you say was happening and the fix to the problem does not make sense to me, but I can not argue with the results. If it now works OK, then I would not worry about how you got there or why its was doing what you had before.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] It was the thermostat [message #272929 is a reply to message #272871] |
Tue, 03 March 2015 08:44 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I once installed 2 temp probes feeding a hand held multi input meter . One in the air stream between the rad and fan and one taped to the stat housing neck. The coolant temp stays almost constant and the air temp swings wildly with driving behavior. Example ---idling at a red light you will get a certain air temp. As you accelerate the temp goes way up for a few seconds and then drops way down as forward motion air fow takes over. I only did this test in the city on a hot day and not on highway or during grade climbs which would trigger fan clutch action.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] It was the thermostat [message #273007 is a reply to message #272894] |
Tue, 03 March 2015 23:13 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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JohnL455 wrote on Mon, 02 March 2015 17:28I like the 195 as well. The temp is more stable as the delta T to the outside air is larger so a proper working stat can modulate the temp at the set point i'm doubting the reason for the fan clutch engagement with the cold stat was the startup fluid redistribution as even in sub zero, GM clutches redist and then turn "off" after a block or so of driving.
I have a 195 as well. Several times I have had my water heater temp/pressure valve pop off while driving. Not sure wether it is pressure from cold water in the tank heating and raising pressure or the probe detects too much heat. I will admit sometime my rig has hit 220 on long climbs but the last time it happened when all remained cool as it was February with no hills. Anyway, I am going to try going back to 180.
Who knows?
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] It was the thermostat [message #273009 is a reply to message #273006] |
Tue, 03 March 2015 23:23 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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The radiator gets more engine heat delivered to it over a longer time when the lower temperature thermostat is partially open, allowing more coolant flow than a higher temperature 'stat.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] It was the thermostat [message #273010 is a reply to message #273009] |
Tue, 03 March 2015 23:34 |
Bullitthead
Messages: 1411
Registered: November 2013
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Should have said "more coolant flow into/through the radiator". Coolant is always flowing if the water pump works and the heater hoses are connected (and unobstructed).
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] It was the thermostat [message #273028 is a reply to message #273019] |
Wed, 04 March 2015 10:30 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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USAussie wrote on Wed, 04 March 2015 06:41Emery,
Thanks for explaining it so well.
Regards,
Rob M.
-----Original Message-----
From: Emery Stora
Hal is right. How you have to think about it is that an engine puts out a given amount of heat. If you try to keep the temperature
of the engine at 180 deg instead of at 195 deg then you have to take away more heat. That heat is transferred to the air flowing
through the radiator. So the air gets hotter because it is transferring more heat to keep the engine at a lower temperature.
As Hal said it seems counter intuitive.
Emery Stora
I guess but once you have driven for say 30 minutes and are getting 10 mpg at 60. (I don't necessarily get that, just makes for easy math) the heat input is fairly constant.
That means I am creating 1.4 million BTUs per hour. Some goes out the exhaust. Some lugs my coach around. Some radiates off the engine. Some heats up the oil. Some has to bleed off at the radiator, probably about 750,000 BTUs per hour. It has to be carried off or you will be sitting by the road, ordering a new engine.
I am thinking a hot piece of radiator metal may give off more heat because of the temperature ratio to ambient. I would think if the water coming from the engine that was 195 degrees the radiator would be hotter than that of an 180 degree engine. The fan clutch could get a breeze from hotter air. The ambient to radiator ratio would be less.
I do know when I was climbing Monarch Pass last September and the temp was hanging at 225, it probably was moot. (I wasn't gett 10 mpg!)
But what do I know. I taught 6th grade.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] It was the thermostat [message #273029 is a reply to message #273028] |
Wed, 04 March 2015 11:00 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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George Beckman wrote on Wed, 04 March 2015 08:30USAussie wrote on Wed, 04 March 2015 06:41Emery,
Thanks for explaining it so well.
Regards,
Rob M.
-----Original Message-----
From: Emery Stora
Hal is right. How you have to think about it is that an engine puts out a given amount of heat. If you try to keep the temperature
of the engine at 180 deg instead of at 195 deg then you have to take away more heat. That heat is transferred to the air flowing
through the radiator. So the air gets hotter because it is transferring more heat to keep the engine at a lower temperature.
As Hal said it seems counter intuitive.
Emery Stora
I am thinking a hot piece of radiator metal may give off more heat because of the temperature ratio to ambient. I would think if the water coming from the engine that was 195 degrees the radiator would be hotter than that of an 180 degree engine. The fan clutch could get a breeze from hotter air. The ambient to radiator ratio would be less.
I do know when I was climbing Monarch Pass last September and the temp was hanging at 225, it probably was moot. (I wasn't gett 10 mpg!)
But what do I know. I taught 6th grade.
Oops. Pretty unclear. A hot radiator would have a greater ambient to radiator temperature ratio. Counter intuitive indeed.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] It was the thermostat [message #273030 is a reply to message #273029] |
Wed, 04 March 2015 11:16 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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George - think about it some more.
The thermostat is just a valve to open the flow to the radiator.
If it closes at 195 deg is will dump less hot fluid to the radiator than if it stays open longer and closes at 180 deg. In order for the engine to get down to 180 degrees it has to give up more heat.
The 180 deg thermostat does not dump 180 deg fluid to the radiator. Nor does the 195 deg thermostat dump 195 deg fluid to the radiator.
In your example of assuming a constant 750,000 BTU per hour would you not agree that to keep the fluid at 180 deg you would have to give up more of that heat to the radiator than if you only want to get it down to 195 deg?
The temperature of the fluid in the engine is not the same as its temperature in the radiator.
Emery Stora
> On Mar 4, 2015, at 10:00 AM, George Beckman wrote:
>
> George Beckman wrote on Wed, 04 March 2015 08:30
>> USAussie wrote on Wed, 04 March 2015 06:41
>>> Emery,
>>>
>>> Thanks for explaining it so well.
>>>
>>> Regards,
>>> Rob M.
>>>
>>> -----Original Message-----
>>> From: Emery Stora
>>>
>>> Hal is right. How you have to think about it is that an engine puts out a given amount of heat. If you try to keep the temperature
>>> of the engine at 180 deg instead of at 195 deg then you have to take away more heat. That heat is transferred to the air flowing
>>> through the radiator. So the air gets hotter because it is transferring more heat to keep the engine at a lower temperature.
>>>
>>> As Hal said it seems counter intuitive.
>>>
>>> Emery Stora
>>
>>
>>
>> I am thinking a hot piece of radiator metal may give off more heat because of the temperature ratio to ambient. I would think if the water coming
>> from the engine that was 195 degrees the radiator would be hotter than that of an 180 degree engine. The fan clutch could get a breeze from hotter
>> air. The ambient to radiator ratio would be less.
>>
>> I do know when I was climbing Monarch Pass last September and the temp was hanging at 225, it probably was moot. (I wasn't gett 10 mpg!)
>>
>> But what do I know. I taught 6th grade.
>
>
> Oops. Pretty unclear. A hot radiator would have a greater ambient to radiator temperature ratio. Counter intuitive indeed.
>
> --
> '74 Eleganza, SE, Howell + EBL
> Best Wishes,
> George
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| Re: [GMCnet] It was the thermostat [message #273033 is a reply to message #273030] |
Wed, 04 March 2015 11:48 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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emerystora wrote on Wed, 04 March 2015 09:16George - think about it some more.
The thermostat is just a valve to open the flow to the radiator.
If it closes at 195 deg is will dump less hot fluid to the radiator than if it stays open longer and closes at 180 deg. In order for the engine to get down to 180 degrees it has to give up more heat.
The 180 deg thermostat does not dump 180 deg fluid to the radiator. Nor does the 195 deg thermostat dump 195 deg fluid to the radiator.
In your example of assuming a constant 750,000 BTU per hour would you not agree that to keep the fluid at 180 deg you would have to give up more of that heat to the radiator than if you only want to get it down to 195 deg?
The temperature of the fluid in the engine is not the same as its temperature in the radiator.
Emery Stora
I agree that a 195* radiator can give off more heat (ambient to radiator heat ratio) than a 180*, but whether the engine is 180 or 195 you still have to get rid of 750,000 BTUs per hour (of the 1.4 million generated by 10 gallons in an hour). I am thinking 99% of it goes out the radiator. I suppose the block gives off more radiant heat at 195 than it does at 180 but in the face of 3/4 of a million BTUs I am thinking 15* is not much help.
Our car block sure doesn't heat our garage much when we pull it in. Oh, wait... Our car is a Volt. Most times the engine has not been running. I suppose the radiator hasn't been doing much, either.. *smile*
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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