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Old 09-04-2018, 06:13 PM   #1
Colonel
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Default Temp diff across Radiator

For a clean radiator, 2 blade fan, working water pump and a 50/50 mix of antifreeze what should one expect to see in temperature difference between the radiator inlet and outlet at say 45mph? I am trying to determine how well my system is or isn't working. I don't have any data or rule of thumb to make judgment. If you have radiator inlet and outlet temperatures those would also be helpful. Thanks
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Old 09-04-2018, 06:34 PM   #2
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Default Re: Temp diff across Radiator

How are you going to measure it at 45 mph?
I’m sure it won’t be a big difference at the high flow rate. You would need a thermocouple in the water stream. Shooting the cast iron is too far off.
If you can drive 45 mph for 10 straight minutes, you have a good core.
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Old 09-04-2018, 06:48 PM   #3
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Default Re: Temp diff across Radiator

Goggle “Rocky Mountain Model A Club Cooling System Presentation”. It will give you all the information needed to understand how the cooling system works.

Model A uses a syphon system aided by a water pump that helps at higher speeds.

Normal temperature difference between outlet at top of engine and inlet at bottom of engine/radiator is around 20 degrees. Syphon starts at around 180 degrees at water outlet top of engine.

Read the Cooling Presentation, it will make you an expert or at least allow you to have a good understanding of how it was designed and works. Enjoy.
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Old 09-05-2018, 05:53 AM   #4
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Default Re: Temp diff across Radiator

I measured the temperature differences several times to see the influence of ambient temperatures. Adding 10F to ambient seems not to add 10F to coolant but less, even theoretically this should be so. After normal ride @ 45mph back in the box I measure a difference between inlet and outlet of radiator of ca. 65F, all measured at the ribs from outside. Top of radiator temperature mostly is 186F, cylinder head close to spark plugs goes up to 205 F under these conditions. Most interesting is the fact that the radiator area covered by the license plate remains totally cool, almost ambient. Seems to be an effect of coolant flow directed by the baffle. Somewhere I also have some pictures from the radiator with a high res- thermocam. If i find them, I will post them also.
Hope that helps
Gerald

Last edited by Gerald1961; 09-05-2018 at 06:01 AM.
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Old 09-05-2018, 12:49 PM   #5
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Default Re: Temp diff across Radiator

Funny you should mention it. See this thread. https://fordbarn.com/forum/showthread.php?t=250406

Also, I've attached a PDF of some calcs I did on the data I have so far.
This data was collected last year, the ambient temp was about 80 deg, and my car, currently, has a 4-blade fan.

Enjoy,
Tom
Attached Files
File Type: pdf ModelAData4.pdf (961.0 KB, 65 views)
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Old 09-06-2018, 10:50 AM   #6
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Default Re: Temp diff across Radiator

Quote:
Originally Posted by Jacksonlll View Post
How are you going to measure it at 45 mph?
Im sure it wont be a big difference at the high flow rate. You would need a thermocouple in the water stream. Shooting the cast iron is too far off.
If you can drive 45 mph for 10 straight minutes, you have a good core.


Very true, driving at 45 for ten minutes on a hot day will tell you if your system is OK. But does not help telling you what is wrong. If a very general rule on temp differential can be developed you would know if you have radiator issue or something else. A hard lesson is spending a lot of time on all the other possible issues to find out like in my case at the end I additionally have a 2 row radiator that is not good enough.
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Old 09-06-2018, 11:51 AM   #7
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Default Re: Temp diff across Radiator

My apoligies, I had not yet read WHN's response when I posted my previous reply. Not knowing better, I am somewhat surprised it is not more than a 20 degree difference from the outlet of the engine, to the outlet of the radiator.


Do I misunderstand?
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Old 09-06-2018, 12:01 PM   #8
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Default Re: Temp diff across Radiator

Some where in the distant past, the Restorer had a comprehensive article on the Model A cooling system. They installed thermocouples all over the engine and the radiator then ran the engine at various rpms. The one thing I remember is that the coolant at #3 & #4 runs hotter. Its the reason why you are apt to have a problem at valves and rings at these cylinders. I'm sure this would show up in the Index. ED
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Old 09-06-2018, 12:19 PM   #9
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Default Re: Temp diff across Radiator

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Originally Posted by 30 Closed Cab PU View Post
My apoligies, I had not yet read WHN's response when I posted my previous reply. Not knowing better, I am somewhat surprised it is not more than a 20 degree difference from the outlet of the engine, to the outlet of the radiator.


Do I misunderstand?
Under ideal conditions, 20 degrees is my understanding of the design range. Assuming everything is operating properly, most importantly the radiator. You need the temperature difference (top to bottom) to have the thermal syphon system work properly. It moves 34 to 36 gallons per minute. Boiling coolant will greatly effect flow.

Cooling system is very simple. It will even work without fan belt or when car is not running.

I highly recommend to anyone that is really interested in understanding the Model A cooling system and how easy it is to trouble shoot problems. To take a moment and read the following.

Please Goggle “Rocky Mountain Model A Club Cooling System Presentation”.

We all have developed our own views on everything in life, but this report is very hard to argue with. Enjoy.

Last edited by WHN; 09-06-2018 at 02:12 PM.
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Old 09-06-2018, 12:28 PM   #10
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Default Re: Temp diff across Radiator

Ok, think I know what my misunderstanding in interpreting WHNs reply. Temps were measured at the engine, not at the outlet of the radiator. So heat from the engine caused water at the inlet of the motor to be hotter than the outlet of the radiator.


In the data provided by MALAK, with the radiator at a stabilized 180 temp, and at driving speeds/rpms with good air flow through the radiator, temp in/out differential of the radiator varies from 30 to 50 degrees.


Malak
Interpreting your data, was the engine cold and showing warm up in the beginning of the data?


Am I correct in assuming you were driving the vehicle, or was the car stationary?


Did your car havea thermostat, find it curious that the coolant temp was so stable at 180 throughout the entire test.


Thanks
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Old 09-07-2018, 12:15 AM   #11
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Default Re: Temp diff across Radiator

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Originally Posted by 30 Closed Cab PU View Post
Ok, think I know what my misunderstanding in interpreting WHNs reply. Temps were measured at the engine, not at the outlet of the radiator. So heat from the engine caused water at the inlet of the motor to be hotter than the outlet of the radiator.


In the data provided by MALAK, with the radiator at a stabilized 180 temp, and at driving speeds/rpms with good air flow through the radiator, temp in/out differential of the radiator varies from 30 to 50 degrees.


Malak
Interpreting your data, was the engine cold and showing warm up in the beginning of the data?


Am I correct in assuming you were driving the vehicle, or was the car stationary?


Did your car havea thermostat, find it curious that the coolant temp was so stable at 180 throughout the entire test.


Thanks
Sorry for the delay answering, I was traveling.
Yes the beginning of the data shows the car warming up.
Yes the car was driven for these tests. The spikes in RPM are me shifting gears.
Yes I run a 180 thermostat. I will be, in the near future, adding individual cylinder EGT probes, and a coolant probe behind cyl #4. Then doing multiple tests with/without thermostat, engine pans, 2/4 blade fans, ignition timing, and whatever other test I can think of.

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Old 09-07-2018, 07:57 AM   #12
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Default Re: Temp diff across Radiator

MALAK - Thanks for the reply. No worries about response time. Your data confirms some suspecions/theory's I have and others have observed. If you get around to the next steps, am looking forward to a similar chart.


Do not remember seeing in this, what radiator are you using , Brand, 3 or 4 row, # of fins?


Perhaps I missed it, what coolant are you using?


Same data without Thermostat would also be interesting, but you would most likely have to record ambient temp and air flow on the engine side of the radiator. Not asking you to do this, just as a matter of discussion.


No rush for your response.
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Old 09-07-2018, 11:38 AM   #13
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Default Re: Temp diff across Radiator

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Originally Posted by 30 Closed Cab PU View Post
MALAK - Thanks for the reply. No worries about response time. Your data confirms some suspecions/theory's I have and others have observed. If you get around to the next steps, am looking forward to a similar chart.


Do not remember seeing in this, what radiator are you using , Brand, 3 or 4 row, # of fins?


Perhaps I missed it, what coolant are you using?


Same data without Thermostat would also be interesting, but you would most likely have to record ambient temp and air flow on the engine side of the radiator. Not asking you to do this, just as a matter of discussion.


No rush for your response.
I'm running 50/50 antifreeze.

The radiator was re-cored by a local radiator shop 42 years ago, when we first got the car. I'm pretty sure it's 4 row and not sure of fin count. I'll verify this info when I get back home next week.

I do have an IAT sensor in the carb which does provide some insight into under hood temps but some additional [ambient] temps could provide interesting info, especially with the engine pan/no engine pan data.

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Old 09-07-2018, 11:52 AM   #14
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Default Re: Temp diff across Radiator

Malak,


No need to reply.


Another possible test is with and without an upper hose coolant filter, have always wondered about possible reduction in coolant flow.
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Old 09-10-2018, 11:02 AM   #15
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Default Re: Temp diff across Radiator

Hi Malak,


One final subject. Are you running a coolant bypass? If yes what type, holes drilled in the thermostat, or something else (details would be nice)?


It is great to see actual data.


Again no worries about response time.


Thanks much.
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Old 09-10-2018, 11:10 AM   #16
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Default Re: Temp diff across Radiator

Quote:
Originally Posted by Ed in Maine View Post
Some where in the distant past, the Restorer had a comprehensive article on the Model A cooling system. They installed thermocouples all over the engine and the radiator then ran the engine at various rpms. The one thing I remember is that the coolant at #3 & #4 runs hotter. Its the reason why you are apt to have a problem at valves and rings at these cylinders. I'm sure this would show up in the Index. ED
Hi ED,


Is the Index a Restorer Index, or an Index on the Barn that I am unaware of?


How do I locate this Index?


Thanks Much
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Old 09-10-2018, 12:30 PM   #17
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Default Re: Temp diff across Radiator

Many indexes are available:

http://www.mafca.com/downloads/Indexes/RINDEX50.pdf

http://www.mafca.com/downloads/Indexes/RINDEX51-60.pdf

http://www.mafca.com/downloads/Index...2Index-all.pdf

http://www.mafca.com/downloads/Techn...Tech_Index.pdf

http://www.mafca.com/downloads/Techn...Tech_Index.pdf
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Old 09-12-2018, 09:20 AM   #18
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Default Re: Temp diff across Radiator

Quote:
Originally Posted by 30 Closed Cab PU View Post
MALAK - Thanks for the reply. No worries about response time. Your data confirms some suspecions/theory's I have and others have observed. If you get around to the next steps, am looking forward to a similar chart.


Do not remember seeing in this, what radiator are you using , Brand, 3 or 4 row, # of fins?


Perhaps I missed it, what coolant are you using?


Same data without Thermostat would also be interesting, but you would most likely have to record ambient temp and air flow on the engine side of the radiator. Not asking you to do this, just as a matter of discussion.


No rush for your response.
So I checked and my radiator is 3 row, 10 fins per inch.
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