What kind of wire? Is it a capillary tube to an adjustable controller, or a on/off switch? Is it threaded into the lower tank, taped against it, ?? If it's near the trans cooler it may not be accurate.

 

Hey Ross,
Yes it's a capillary tube to an adjustable controller. It's not threaded on there - more rudimentary sort of taped or some sort of "mud" puddy stuff. The trans cooler is on the other side of the radiator but down low as well.

Ben in Austin

 

Why not try running the fan direct through a toggle switch to the fan relay. That way you determine if it is a fan speed or fan thermostat problem.

 

When sensing off the lower tank, temp setpoints are 30 deg or so lower. I don't know if I'd trust a sensor that isn't immersed. A manual override isn't a bad idea.

 

I run 1980 degree thermostats and set my fans to come on at 190 degrees. Once they are on they are pretty much on, but I run OEM stuff so they are designed to run continuously as if the A/C were on.
Capillary style sensor should be at the thermostat outlet, normally the upper radiator hose area. Adjust the pot on the controller to turn on the fans at 190 degrees or where ever you want it.
If your fan is in the engine compartment make sure it is pulling air into the engine compartment and not trying to push it out, they can be wired backwards.

 

I'm probably going to hurt some feelings, and likely going to get some arguments, but there is a lot of old wives tales, half truths, and misunderstandings on how a cooling systems (are supposed to) work. Here's the unembellished truth based on proven scientific facts and automotive/race engineering:
1. A radiator is a water to air heat exchanger. Water gains heat in the engine caused by the combustion of the fuel and air. The heated water is pumped through the small thin passages in the radiator where cooler air surrounding and passing between those passeges picks up the heat and dissipates it into the atmosphere. The cooler water returns to the engine to repeat the cycle. There are only a few simple physical facts that can influence the effectiveness of the process. a.) the difference in temperature between the heated water and the air. The larger the difference the more efficiently the heat exchanger works. The heat transfer (cooling) is much more efficient when the surrounding air is colder. b.) the number and size of the radiator passages and fin count and the radiator construction materials. The more passages and fins the air comes in contact with the more heat will be transferred. The efficiency can be increased by adding more passages, called rows in the trade, and increasing the number of fins per inch of tube. The construction material will affect the transfer because they transfer heat at different rates. Copper transfers best of the commonly used materials, followed by aluminum, brass, and then steel. (These materials have secondary properties of galvanic and aqueous corrosion as well as cost and durability that must be considered in selection and operation.). c.) the quantity of air passing through the radiator. This can be affected by the speed of the vehicle, and/or forcing air to pass through the radiator by use of a fan. When using a fan, pulling the air through the radiator is much more efficient than pushing it. You should never use two fans, one pushing and one pulling! A fan is rated by how much air it moves, usually rated in cu ft /min. d.) the heat transfer rate and boiling point of the coolant. (if the coolant boils, it becomes a gas, and a gas is never as good as a liquid for heat transfer). d.) the rate of the coolant moving through the radiator. Typically the more coolant that flows through the radiator the more it will be cooled, but that has a point of diminishing returns. If the coolant flows too quickly it may not spend enough time in the radiator to cool as much as possible.
THAT'S ALL FOLKS! as Porky Pig used to say.

2, Note that the thermostat was NOT included in factors affecting the cooling rate! That's because it doesn't. Let's now discuss what the thermostat's role IS in the cooling system.
An internal combustion engine is increasingly more efficient the hotter it gets!!! More heat is being used to produce power rather than to heat the surrounding engine parts. Also the hotter the combustion the more efficiently (completely) the fuel is burned. Running an engine too cool produces a lot of water vapor and by products that condense in the exhaust and crankcase. If the combustion water is not boiled off it will combine with the by products to form acids and sludge, deadly combinations. This is why a lot of very short jaunts are far worse than a few longer trips. Back to the thermostat. The thermostat is like an automatic on and off switch for the coolant to pass through the radiator. It stays in the closed position when the coolant is cold preventing the water pump from circulating the water through the radiator and forcing a small amount though a bypass back into the engine until the coolant in the engine reaches the opening temperature of the thermostat (indicated by it's rating in *F in the US) when it opens fully and the water can then pass through the radiator. IMPORTANT! so I will repeat: The thermostat rating has absolutely nothing to do with the final temperature the engine will reach, only how soon the coolant will be allowed to circulate through the radiator. PERIOD! A higher rated thermostat is usually more desirable because the coolant in the engine will reach the temperature needed to produce more power and boil off the water vapor condensed in the crankcase and exhaust (and start producing heat from the heater in cold weather) sooner. NEVER operate the vehicle with the thermostat removed. This will keep the engine from reaching it's operating temp without producing a lot of byproducts and may allow the coolant to circulate too quickly to cool efficiently, see 1. d.) above.
3. Water Wetter = "snake oil". Water can be made wetter (closely contacts a surface) by adding a small amount of a surfactant (detergent). BUT unless you are racing in a series that requires you to use plain water coolant (some NHRA and NASCAR series for example, where it may be dumped on the racing surface. Antifreeze is very slippery to tires and difficult to clean off the racing surface.) you should ALWAYS be using a 50/50 mix of a good antifreeze and water in your cooling system, and the antifreeze already contains all the surfactant needed. Putting a product like Water Wetter in your radiator properly filled with water and antifreeze does as much good as pouring it on the ground. Antifreeze should be used year round because it not only lowers the freezing temperature of the water, but it also raises the boiling temperature above 212*F making a boil over less likely. As already discussed it also contains surfactants and (rust and galvanic) corrosion inhibitors. The effieciency of the additives decrease with age, so the cooling system should be flushed and refilled periodically. Never run just antifreeze either.

4. Wind deflectors, radiator shrouds, etc. You want the air to move through the radiator, not around it. All our trucks came with air deflector panels that surrounded the radiator and blocked the air from bypassing the radiator. Air will flow through the path of least resistance, so make sure those or similar solid panels and rubber seals remain in place on both sides as well as top and bottom around the radiator. I don't know how many hotrods I've seen with beautifully made deflector panels on each side of the radiator and nothing between the top of the radiator and hood, or a big gap where the rubber seal should be. A 4" open hole in the deflector will flow more air than the entire radiator. If used with deflector panels a fan shroud can be effective to a point. If the opening is too small, the fan blades too numerous or wide, and/or the fan turning at too low a speed it can block more air than direct it, If you engine runs hot at speed but not around town you may be blocking the air rather than directing it. You might try first removing the shroud, then using a larger/higher speed fan or adding pressure relief flaps to the shroud.

 

Good write up AX! I was downloading a movie and needed to sit patiently and let it finish. Reading that filled in the time

 

Hey Ax,
You are killing me over there. I was off a the doc's this afternoon so I enjoyed reading through that - knowledge is always good.
Let me take a look at all the thoughts & ideas & formulate a plan. I really want to get this one right - an overheating truck in Texas isn't going to get to play often.

o 180 Degree thermostat - I like the idea of coolant flowing at a slightly lower temp than the stock 195 degrees.

o I do think I'll re-engineer the Fan set up to ensure that the fan turns on around 190 degrees & the higher CFM setting kicks in around 200 degrees.
I may also move the sensor up higher in the radiator.

o I haven't done anything to improve air flow through the radiator.
(Does anyone have a pic of the stock ones that came on a 1950?)
I'll look at blocking up the air flow area around the radiator.

Is there a point of view on the Transmission cooler? Is that cooling capacity
coming at the expense of the engine? Is it necessary?

Thx
Ben in Austin

 

1. lower temp thermostat: no affect unless you do a lot of short drives in the winter. be sure engine gets to max temp > 200* for 10 -15 min before shutting it off.

2. Fan switch position: no opinion I don't believe it to be critical if adjustable, as long as set temp is not undercooling or overcooling. I'd use an infrared thermometer at the top of radiator to adjust the switch.

3. water cooling of tranny is CRITICAL with an automatic, the fluid and friction materials in an auto are even more sensitive to too high or too low an operating temp than the engine. Circulating the fluid thru the radiator is actually more about keeping it in the proper designed relatively narrow operating temp range, especially when starting out cold, than it is in cooling it. The auto doesn't get overly hot to add heat load except when pulling a load or slipping.

 

Here are a couple shots of F1 air deflectors: side deflectors #13068,9. lower deflector and seal #8208, # 8348

Side deflector behind headlight. Closes in from inner fender panel to outer edge of fender.



Part 16613 upper deflector under hood. I believe there was a rubber seal where it sat over radiator top. I'm not an expert on F1's but I'm learning helping Tonyb55.

 

If the sensor is at the bottom tank, it needs to be WAY less than 200 degrees. That is the temperature after the radiator has already done its job cooling. The temp going in is typically 25 - 30 deg hotter.

The advantage of having the sensor at the bottom is that if the coolant is cool enough leaving the radiator without a fan running, you don't want to run it even if the coolant is 210 going in. Example: going up a long steep hill in 50 deg weather.

If the sensor is at the top tank, it reacts to engine load more quickly, but may do so unnecessarily (in cool weather again).

Worth noting -- almost all EFI engines from the factory turn off the fans above 35 mph, even with A/C running. The fans just can't move any more air than the vehicle's speed provides.

 

Thanks Ax for the diagram - I'm going to check out the front air deflectors to see what we are missing.

Hey Ross,
Define "Way Lower" if we use the 180 degree thermostat & the sensor stays at the bottom of the radiator - where should we set the (2) Fan speeds to come on?

I appreciate the help from everyone - I'm trying to fully understand how the cooling system is supposed to work so all the pieces work together efficiently. Like most of our trucks our's is put together from a lot of non-stock parts installed over a couple of years. Not sure we got it all right up front - I was just happy to get it back together & have it run. Now I'd just like it to not run hot...

Noone is mentioning the Header Wrap - So that doesn't make much of difference in the end? Concentrate on air flow & water flow....

Ben in Austin
1950 F1

 

Hi Ben,
Could you share a picture of your fan shroud? If it is not sealed well to the radiator, it won't work well. Seems like I'd first look at air flow at low speeds and idling, given the problems you cite.

As AX said, air wants to find the path of least resistance. My SPAL fan with homemade shroud is keeping my engine cool even in hot ambients (90F to 100F). It is a 16" with 2000-ish CFM rating and draws about 22amps. This is with the AC running. Mine comes on about 200F degrees (as seen by engine PCM) and the temp drops down to the point at which the thermostat opens ~ 192F.

I did seal the shroud to the outer shell of the radiator with Bulb seal Style 6 here: McMaster-Carr

Is your shroud well sealed to the radiator?

Given the current draw, it is critical to use larger wire. A large voltage drop across the wiring itself will definitely slow down the fan. Did you wire the fan with 10 gauge wire? This chart says a 20amp load with 15' of wire requires 10 gauge: Amps and Wire Gauge - 12V Circuit

Remember:
The higher the temperature delta between the coolant and the ambient air temperature the more heat transfer will take place given constant 1. fluid (coolant) flow within the radiator and 2. air flow across the radiator fins. (AX stated this clearly, forgive the restatement)

This is one reason that neither the 180, 190, 200, 210 will not cool better once each is wide open. For that reason, I left the stock thermostat in my 6.2L transplant engine. More airflow across the radiator, hopefully, will do the trick for you.

Another tip: if you don't have one, the Harbor Freight IR temperature gun is really awesome. Best $25 (or $40 - can't remember) I've spent on a tool.

Doug

 

You asked for pictures, I believe. This is the original shroud, modified for the fan that is cooling my 360 CID SBC. I have the fan toggle switched through a relay, no fan thermostat. I like to think I am in control and aware enough to drive the truck, not having something happen automatically. With any road speed at all, I do not need the 2400 CFM fan. In traffic, the engine runs at 180 deg.

 

Hey Doug,
I'll take a pic of our Fan set up when my son Zack get's back from
his Hot Wings run. So your fan comes on at 200 & cools it back down to the Thermostat temp. - we aren't seeing that at all.

I appreciate the visual on what you have done. That helps me
to understand a bit better. I may need to take our cooling set up
back off & reinstall it with more thought this time. It works but I really need it to be rock solid - I hate driving around worrying about overheating.
(Taking that darn fan off of the ignition circuit would help with starting as well - It's tough to start with that fan pulling amps from the battery too).

I appreciate it - photos to come.

Ben in Austin
1950 F1