Cooling System Troubleshooting guide

[grubby65]

Has anyone ever come across a good guide for troubleshooting the radiator/cooling system for a car. I'm a mechanical engineer who deals a lot with heat exchangers, we have specification sheets that tell us what amount of temperature changes we should see on the cold and hot side. I have a cooling issue with my 64 Polara and I would rather diagnose the system so I can make the correct changes rather than just throwing parts at it. Basically there will be a temperature change across the water going through the radiator and also a change of air temperature for the air going across the fins. If you knew a range of what those should be then you could determine if it is an air flow issue or a heat exchanger (radiator) issue. Most of the articles I have read have been more a sales promotion for a particular product.

 

[eric383]

How about this?
http://www.saldanaracingproducts.com/Cooling System Principles.pdf

 

[Frank Mopar]

Tell us with the problem is. I'm sure someone here has addressed it and can better help you out

 

[Yatzee]

Has anyone ever come across a good guide for troubleshooting the radiator/cooling system for a car. I'm a mechanical engineer who deals a lot with heat exchangers, we have specification sheets that tell us what amount of temperature changes we should see on the cold and hot side. I have a cooling issue with my 64 Polara and I would rather diagnose the system so I can make the correct changes rather than just throwing parts at it. Basically there will be a temperature change across the water going through the radiator and also a change of air temperature for the air going across the fins. If you knew a range of what those should be then you could determine if it is an air flow issue or a heat exchanger (radiator) issue. Most of the articles I have read have been more a sales promotion for a particular product.

It is difficult to know the exact problem unless you know what combination engine/cooling system was in the car originally and if that configuration still exists. Obviously things worked great when the car left the factory so the question ( and solution) is, "What's been changed since then?". Different combinations of cooling systems components can render a wider or narrower temperature differential from when the liquid leaves the engine to to when it returns to the engine. As you know, the secret is to have a large efficient enough cooling system to overcome engine heat under any condition. So in theory you could have a huge radiator with little air flow or a smaller unit with huge airflow, the wrong thermostat to deal with latent heat dissipation, wrong timing of the engine and a host of other issues including the effective air opening in the front of the car. Experimentation is the only way to deal with some issues, others are as easy as trimming your nails. You can, in fact, find the values you seek by talking with people who have "Been there, done that" or contacting the manufacturers of various components and requesting their engineering data ( unless it's pure Chinese made) for thermostats, radiators, hoses and cooling fans be they mechanical or electric. More info on your particular issue whould be great if indeed you have an issue.

 

[grubby65]

Tell us with the problem is. I'm sure someone here has addressed it and can better help you out

The car is a 1965 Polara, the motor is a 400/500 cubic inch with aluminum heads. Approximate rating on the motor is 550 hp. It has air conditioning, automatic transmission (with a stand alone cooler), high flow water pump, no thermostat. The fan is a 17" flex, no clutch, with shroud. The radiator is a 22", 4 core champion. If the ambient temperature is below 80 degrees I have absolutely no problems overheating. I can drive it all day long, let it set for long periods of time with no issues. When the ambient temperature gets above 90 then I have problems. It will run up to 210 degrees no matter what, driving or idling. The electric fan seems to have no affect on the temperature of the coolant. This is without running the air conditioning.

 

[black64]

A thermostat regulates coolant flow and to remove heat, and coolant flowing to fast through the radiator won't allow enough heat to be removed. You have high flow pump and no thermostat this could be a reason at higher temps your system can't handle it.

 

[69 GTX]

Put in a 185 thermostat

 

[Mike67]

Is the sensor installed in the original factory location? Different locations can skew the reading.
Being an engineer that deals with heat exchangers you know that gpm will affect the exchange rate, if you don't have a t stat to restrict the flow & allow it to spend enough time in the radiator, you will not meet the design criteria of that radiator. Don't remember the formula, it's been a while since I dealt w/ CHW exchangers...and would require the design specs which I have no idea how to get... I'm not even sure what the design delta is on a radiator 20-30F +/-???

 

[grubby65]

Is the sensor installed in the original factory location? Different locations can skew the reading.
Being an engineer that deals with heat exchangers you know that gpm will affect the exchange rate, if you don't have a t stat to restrict the flow & allow it to spend enough time in the radiator, you will not meet the design criteria of that radiator. Don't remember the formula, it's been a while since I dealt w/ CHW exchangers...and would require the design specs which I have no idea how to get... I'm not even sure what the design delta is on a radiator 20-30F +/-???

I really don't know what the design temperature drop would be, a lot of it depends on the temperature of air going across it. The thing we all need to remember is the cooling system for a vehicle is a closed loop, so the time in the radiator is kind of irrelevant. While the coolant spends less time in the radiator it also spends less time in the motor. Without getting too technical, if you have the same amount of BTU's being put into the coolant from the motor, the more flow (#'s/hr) going through the motor the less the temperature of the coolant will be raised. I don't know if I'm making sense here, you are correct in assuming the increased coolant flow through the radiator will reduce the actual temperature drop of the coolant but the BTU removal should be the same. On the other side of the coin the increase flow of coolant through the motor will decrease the temperature rise of coolant while it is in the motor. The definition of a BTU is the amount of energy required to change the temperature of 1 pound of water by 1 degree F. In all reality the job of a thermostat is two fold, one is to help the motor get to temperature quicker the other is to maintain the temperature as close as possible to set temperature. One question would be, when the thermostat is wide open how much restriction does it actually provide? One benefit I can see from the thermostat it would provide a certain amount of back pressure in the cooling passages of the motor which might help with flashing of the coolant. The person who built my motor, who is actually another mechanical engineer, told me he never puts a thermostat in any of the motors he builds, for what that is worth. Not trying to come across as being too intellectual.

 

[Mike67]

You are not lol! You are correct regarding it being a closed loop and btu rise and it makes sense talking about it. You also have to take into account the pressure relationship on the system as well as media, cast iron vs aluminum/ copper ect. In a previous life I dealt with a lot of plate frame exchangers as well a tube and shell.
The time variable has as much to do with max exchange rate efficiency as does OAT/GPM/CFM. If one mfg rates his radiator at 95F w/ 1200cfm & 42 gpm & another rates his at 90F 1500cfm & 55 gpm there is going to be a variance in performance.That does not even account for the differential of the air flowing across/through the radiator...
The t stat is dual purpose, 1- to get the motor up to operating temp quickly, 2- to provide enough of a restriction to control the flow through both the radiator and block and even at temp when it's wide open it is still significant I would think. Look at the stem size compared to the orifice it sits in JM.02
If you find any engineering data on which mfg you are currently using I would enjoy seeing it.
Good luck

 

[Yatzee]

Has anyone ever come across a good guide for troubleshooting the radiator/cooling system for a car. I'm a mechanical engineer who deals a lot with heat exchangers, we have specification sheets that tell us what amount of temperature changes we should see on the cold and hot side. I have a cooling issue with my 64 Polara and I would rather diagnose the system so I can make the correct changes rather than just throwing parts at it. Basically there will be a temperature change across the water going through the radiator and also a change of air temperature for the air going across the fins. If you knew a range of what those should be then you could determine if it is an air flow issue or a heat exchanger (radiator) issue. Most of the articles I have read have been more a sales promotion for a particular product.

I see two significant problems with your cooling system that you may be able to remedy and one not so conventional. Your A/C condenser is probably causing at least a 35% reduction in air flow through the rad being mounted so close. On a 22 inch rad you need a ton of air coming out the back side of the rad, about 2000 cfm or more. I have a 512 stroker and here's my system: 160 degree thermostat, Derale 16 inch Tornado fan with a 1 1/4 deep full shroud, Dakota Digital fan controller with the sensor mounted in the heater loop at the water pump outlet where the engine temperature is accurate for fan off/on. Mine is a 22 inch OE radiator. I had a Champion aluminum one but their garbage at 630 H.P. I also use a 16 lb rad cap (OE) to maintain good coolant pressure in the block and reduce steam pockets. All of my heat is generated by the middle siamese pistons. I'm sure my TTI headers dump a load of heat out through the exhaust system. I know a 22 inch rad is cutting it close for capacity and I can't afford a $8000 engine going down the toilet due to ineffective cooling so I needed a bit more cooling capacity with a higher volume of coolant. I installed some passive cooling by mounting a pair of 3 x 21 x 2 inch heater cores below the rad and feeding them with coolant coming directly from the engine via the heater outlet/inlet ports at the water pump housing. I have no use for a car heater, do not want to butcher my core support and didn't want to pay $800 for a new rad. The tubes in the heater cores are a full 1 3/4 wide and really pull the heat out of the engine. The car runs at 180 all day regardless of driving conditions or the weather. As you can see by the photos, air comes from under the front of the car at higher speeds, radiates up so the main cooling fan can blow the heat away at lower speeds and is damn near hidden. In effect, I have added 132 more square inches of cooling surface and it works damn fine.

 

[grubby65]

I see two significant problems with your cooling system that you may be able to remedy and one not so conventional. Your A/C condenser is probably causing at least a 35% reduction in air flow through the rad being mounted so close. On a 22 inch rad you need a ton of air coming out the back side of the rad, about 2000 cfm or more. I have a 512 stroker and here's my system: 160 degree thermostat, Derale 16 inch Tornado fan with a 1 1/4 deep full shroud, Dakota Digital fan controller with the sensor mounted in the heater loop at the water pump outlet where the engine temperature is accurate for fan off/on. Mine is a 22 inch OE radiator. I had a Champion aluminum one but their garbage at 630 H.P. I also use a 16 lb rad cap (OE) to maintain good coolant pressure in the block and reduce steam pockets. All of my heat is generated by the middle siamese pistons. I'm sure my TTI headers dump a load of heat out through the exhaust system. I know a 22 inch rad is cutting it close for capacity and I can't afford a $8000 engine going down the toilet due to ineffective cooling so I needed a bit more cooling capacity with a higher volume of coolant. I installed some passive cooling by mounting a pair of 3 x 21 x 2 inch heater cores below the rad and feeding them with coolant coming directly from the engine via the heater outlet/inlet ports at the water pump housing. I have no use for a car heater, do not want to butcher my core support and didn't want to pay $800 for a new rad. The tubes in the heater cores are a full 1 3/4 wide and really pull the heat out of the engine. The car runs at 180 all day regardless of driving conditions or the weather. As you can see by the photos, air comes from under the front of the car at higher speeds, radiates up so the main cooling fan can blow the heat away at lower speeds and is damn near hidden. In effect, I have added 132 more square inches of cooling surface and it works damn fine.

View attachment 444923 View attachment 444924 View attachment 444925

I might be able to move the condenser an inch or so farther away from the radiator. Do you think the would be sufficient. Have you ever had any issues with debris (rocks) hitting your heater cores?

 

[Yatzee]

I might be able to move the condenser an inch or so farther away from the radiator. Do you think the would be sufficient. Have you ever had any issues with debris (rocks) hitting your heater cores?

Not at all. If you look closely, you'll see my tranny cooler tucked up under the front bumper. It's cooled using 2 Spal 4.5 inch, 3.5 amp silent fans also run off a Dakota Digital controller. No sense heating the tranny via rad water or heating rad with a tranny loop inbeded in the bottom tank. My power steering fluid cooler is up under the left fender as the pump not only does the steering box but my hydro boost brake unit as well. There's some really good articles online for engine heat control and simple applications that don't cost a fortune. I saw an article where a fellow with a 700 hp hemi used two slant-fin heater tubes out of old baseboard heaters attached to the underside of his car and pulled the temp down by 30 degrees. He got them at a metal recyling yard for $10 apiece and $15 for the hoses. They're up there completely out of sight.

 

[69 GTX]

What is the optimum distance between the AC condenser & radiator?

Just looked on the Griffin site, .188-.375 is the recommended space.

 

[Frank Mopar]

I would pull the ac condensir right off and see if that fixes it. Might be kicking a dead horse if that's not the problem.

 

[grubby65]

On a somewhat unrelated subject. I noticed there is a gap between the top tank of the radiator and the support. It would probably help if I sealed this up. What are you guys using to seal this area?

 

[69 GTX]

I used 1" x 1/2 adhesive foam (I called it topper foam, similar to what is used to seal toppers to bed rails on pickups.

 

[69 GTX]

Here's a picture of the foam filling the gap on shroud.View attachment 403848

 

[Yatzee]

Has anyone ever come across a good guide for troubleshooting the radiator/cooling system for a car. I'm a mechanical engineer who deals a lot with heat exchangers, we have specification sheets that tell us what amount of temperature changes we should see on the cold and hot side. I have a cooling issue with my 64 Polara and I would rather diagnose the system so I can make the correct changes rather than just throwing parts at it. Basically there will be a temperature change across the water going through the radiator and also a change of air temperature for the air going across the fins. If you knew a range of what those should be then you could determine if it is an air flow issue or a heat exchanger (radiator) issue. Most of the articles I have read have been more a sales promotion for a particular product.

It occurs to me that you are running two fans on your rad - one mechanical on the inside and one electric on the front side. Why? The outer one produces an air flow that is concentrated within the diameter of the fan only, yet the inner one has a shroud. If this doesn't create enough air flow thru the rad then I'd have to question the efficiency of the rad itself or the BTU's that the engine is actually putting out. Between the two fans, you've probably got about 3500 cfm of air flow. Obviously there's not enough engine heat coming to the surfaces of the rad for proper cooling when both fans are in operation. Perhaps it's time for a complete re-evaluation of your cooling system.

 

[oldbee]

69gtx and others. Condensers are usually pretty close to rad to get air flow at idle&close to it. Doesn't matter the vehicle type- cars,semi's etc.