September 1972
Jr. Member
- Joined
- Apr 27, 2017
- Messages
- 136
A month ago I performed a cooling system test on the Bronco in 100F ambient temperature here in the San Fernando Valley which is located in the northern part of Los Angeles. The vehicle was stationary with the hood open and the results we're inconclusive insofar that I need to have the test done on videotape and have to watch it because I was alone at the time and did not want to overheat the Bronco. The thermostat housing was between 195F and 210F and started to climb when I decided to abort the testing procedures.
Using two temp guns on the exhaust manifolds, heads, and radiator and hoses and other locations, the temperatures we're flip flopping when the thermostat opened and closed. A hot manifold became cooler and a cool manifold became hotter and so forth.
The coolant flow might be disrupted by a restriction in the head or elsewhere which caused more coolant flow through a neighboring coolant jacket is one possible scenario.
The aluminum radiator might be the problem insofar as the flow and cooling characteristics are not the same as the stock radiator which Ford engineers designed for this application. Fluid dynamics is a very complicated field of engineering and a larger radiator can damage a engine because the thermostat closes too early before the heat is scavenged out of all parts of the engine and the water pump plays a critical role as well.
For example. The 195F thermostat opens and the large flow water pump moves the coolant out of the upper hose and down through the large aluminum radiator then through the bottom hose into the engine block then up through the heads and back to the top hose of the radiator. My temperature split was 20 to 40 and erratic which is not good, it should be 25 to 30 steady measuring the temperature of the top and bottom hose. I am beginning to strongly suspect the radiator and water pump but more tests are required.
If my suspicions are correct, the non factory radiator and water pump do such a good job in removing heat that the thermostat closed BEFORE the heat in certain parts of the heads and block had a chance to transfer their heat to the coolant. The process is repeated and the result is an engine with hot and cold spots instead of a nice even temperature throughout the entire engine which was the intent of Ford engineers.
Big tats on a lady does not necessarily mean the whole package is a tasty treat and in fact it might be downright nasty, the same thing applies here with water pumps and radiators.
Therefore, the areas of the engine which have not been provided enough time to transfer it's heat to the rapidly moving coolant, usually at the rear cylinder heads because of the normal velocity drop when the cooled coolant enters the engine block, heat up. The coolant at these areas will/may heat up beyond the limits of the 50/50 antifreeze and a 13 pound cap to about 260F which will cause a change of state of liquid to gas. This may cause a boil over when the engine is running but usually will occur when the engine is turned off because when the engine is running the gas is dispersed in the cooler parts of the coolant within the engine and turns back to liquid, but when the engine is turned off the gas will run unhindered in a pressure wave and slam into the cap which will overwhelm the spring and release the gas and coolant pressure wave.
My next step is to ensure that my A/F ratio is correct and the timing is right. I have a re curved distributor which is designed for 18 initial and an advance curve from 1300 RPM to 2200 RPM of 16 for an all in of 34. Retarded initial engine timing is a smog feature and there is nothing good about it, it holds in heat. When you apply 18 initial timing do you notice how free and easy the engine runs? That because the engine is happy there. My distributor guy checks his distributors on a machine and the advance is perfect, the red laser dots line up as the speed is increased within the mechanical advance range and as he pulls it past the mechanical advance stop at 2200 RPM to 5000 RPM there is no spark scatter. The only method to confirm that a distributor is working properly is this machine, a good timing light might show spark scatter but it's hit and miss.
Another step is to install 10K sensor rings under the spark plugs and on each exhaust manifold next to the cylinder and check the actual temperatures in operation. If they are not even as they should be, the upper radiator hose will be slightly pinched off to look for a positive change in even temperatures without creating a general overheating condition. If that doesn't work I'll try changing the pump to a lower flow model but my gut tells me that there is a restriction caused by corrosion blocking some small coolant holes or improper installation of intake manifold or head gaskets and an oversized radiator and water pump.
I hope this might help out some of you out there with cooling problems since understanding how things work is the first step to figuring out a solution.
Using two temp guns on the exhaust manifolds, heads, and radiator and hoses and other locations, the temperatures we're flip flopping when the thermostat opened and closed. A hot manifold became cooler and a cool manifold became hotter and so forth.
The coolant flow might be disrupted by a restriction in the head or elsewhere which caused more coolant flow through a neighboring coolant jacket is one possible scenario.
The aluminum radiator might be the problem insofar as the flow and cooling characteristics are not the same as the stock radiator which Ford engineers designed for this application. Fluid dynamics is a very complicated field of engineering and a larger radiator can damage a engine because the thermostat closes too early before the heat is scavenged out of all parts of the engine and the water pump plays a critical role as well.
For example. The 195F thermostat opens and the large flow water pump moves the coolant out of the upper hose and down through the large aluminum radiator then through the bottom hose into the engine block then up through the heads and back to the top hose of the radiator. My temperature split was 20 to 40 and erratic which is not good, it should be 25 to 30 steady measuring the temperature of the top and bottom hose. I am beginning to strongly suspect the radiator and water pump but more tests are required.
If my suspicions are correct, the non factory radiator and water pump do such a good job in removing heat that the thermostat closed BEFORE the heat in certain parts of the heads and block had a chance to transfer their heat to the coolant. The process is repeated and the result is an engine with hot and cold spots instead of a nice even temperature throughout the entire engine which was the intent of Ford engineers.
Big tats on a lady does not necessarily mean the whole package is a tasty treat and in fact it might be downright nasty, the same thing applies here with water pumps and radiators.
Therefore, the areas of the engine which have not been provided enough time to transfer it's heat to the rapidly moving coolant, usually at the rear cylinder heads because of the normal velocity drop when the cooled coolant enters the engine block, heat up. The coolant at these areas will/may heat up beyond the limits of the 50/50 antifreeze and a 13 pound cap to about 260F which will cause a change of state of liquid to gas. This may cause a boil over when the engine is running but usually will occur when the engine is turned off because when the engine is running the gas is dispersed in the cooler parts of the coolant within the engine and turns back to liquid, but when the engine is turned off the gas will run unhindered in a pressure wave and slam into the cap which will overwhelm the spring and release the gas and coolant pressure wave.
My next step is to ensure that my A/F ratio is correct and the timing is right. I have a re curved distributor which is designed for 18 initial and an advance curve from 1300 RPM to 2200 RPM of 16 for an all in of 34. Retarded initial engine timing is a smog feature and there is nothing good about it, it holds in heat. When you apply 18 initial timing do you notice how free and easy the engine runs? That because the engine is happy there. My distributor guy checks his distributors on a machine and the advance is perfect, the red laser dots line up as the speed is increased within the mechanical advance range and as he pulls it past the mechanical advance stop at 2200 RPM to 5000 RPM there is no spark scatter. The only method to confirm that a distributor is working properly is this machine, a good timing light might show spark scatter but it's hit and miss.
Another step is to install 10K sensor rings under the spark plugs and on each exhaust manifold next to the cylinder and check the actual temperatures in operation. If they are not even as they should be, the upper radiator hose will be slightly pinched off to look for a positive change in even temperatures without creating a general overheating condition. If that doesn't work I'll try changing the pump to a lower flow model but my gut tells me that there is a restriction caused by corrosion blocking some small coolant holes or improper installation of intake manifold or head gaskets and an oversized radiator and water pump.
I hope this might help out some of you out there with cooling problems since understanding how things work is the first step to figuring out a solution.
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