Cooling System
Recently I flushed the radiator and exchanged my 192 degree thermostat for a 180 degree at the recommendation of many for an older 351 Cleveland. Saturday the boy and I drove about 5 miles to the gas station. Then about 7 miles to the park. Was there for about an hour. Then we drove 7 miles to lunch. Followed by 5 miles back home. No issues whatsoever until the next morning when I noticed a wet spot under the front end. It was coolant and it's coming from the overflow nipple and hose on the radiator.

I had this happen a few weeks ago when I let the car idle in the driveway for about 5 minutes. This too was after the 180 degree thermostat. It didn't happen immediately after shutting down. Somewhere between 30-60 minutes after we returned to the garage. I just dismissed that as maybe the car idling too long with no air flow.

Another item to note was after flushing the cooling system. I let the car sit with the hoses disconnected overnight. The next day I hooked them up and started adding new fluid. I added 1 gallon of coolant concentrate and then 1 gallon of distilled water. I then started to add the 2nd gallon of coolant and 2nd gallon of distilled water.

I only got about half the 2nd gallon of coolant in the radiator. This meaning the car had 1 1/2 gallons of coolant and 1 gallon of distilled water. Every book I read says 16 quarts which if my memory from school is correct would be 4 gallons.

Where I stopped was about 2" below the neck of the radiator cap. Even after the car purges only after being put to bed and cooled off the fluid level in the radiator is in the same spot.

So my train of thought goes in two directions here. I either have too much coolant in the system and when hot it's purging a small amount overboard. I'm guessing this might happen when the thermostat closes back up? My second idea is that the car's cooling system was working better with the 192 degree thermostat?

I can also add that with the 180 it only gets to about a needle width below to about a needle width above on the temp guage. With the 192 degree thermostat it ran between about 1/4 - 1/2 way up the temp guage. I also recently changed the belts because they were beyond there life span. So I know the fan is actually spinning properly instead of the belt slipping more than turning the fan. The temperature was about in the mid 80's where I'm at these past two times this has happened. If I had to guess the amount of coolant coming overboard I'd guess a cup or two.

Thoughts? Thanks!
Although the coolant is PRESSURISED it will EXPAND as the tempreature goes up. If you FILL the radiator cold, run the engine up to normal temp and let it cool coolant will have been expelled and if you check the level it will appear 'down'.
To over come this fit a coolant recovery tank so the radiator is always 'full'. This also slows corrosion as you are preventing air (oxygen) being introduced into the system.
I would pressure test the radiator cap. If you don't have a means to pressure test the radiator cap, simply replace it. Just like M1FF mentioned, it's very common for people to add an overflow tank to these older cars to catch small amounts of coolant that occasionally come out of the overflow hose. I have one on mine. It hasn't caught anything yet. If you ever watch the overflow tank in your daily driver, the coolant level in it typically rises and lowers a very noticeable amount as the engine heats up and cools down.

It sounds like there are no other cooling symptoms. It doesn't run too hot and the temperature gauge is stable? What thermostat was in installed when it spit out a little coolant? Some people like the higher temp thermostats in these older cars. I prefer 180 at most in them.

If you think about the path the coolant has to travel to exit the block you will understand why after back flushing a system its almost impossible to get all the water out of the block. The water below the water pump level will stay in the block. I lift the back of the car with a floor jack to get more coolant out of the block. Was the car at least level when you drained the coolant?

So now you have a total of 1 1/2 gallons of antifreeze and 2 1/2 gallons of water with 1 gallon of that water being distilled. What I have done in that situation is drain some coolant and refill with straight antifreeze. Its not perfect but still closer to 50/50. Then save the drained coolant for future top offs on all your vehicles.

Cooling system woes have been troubling people for years. The time-worn and "obvious" fixes to cure a hot-running engine are in reality not always effective, even though intuition tells us they should be.

1) Running a cooler thermostat (or no thermostat) will almost never solve a hot-running engine problem. That is because the thermostat controls the temperature of the coolant...not the engine. The reason that newere cars have such high-temp thermostats is to allow the coolant to take as much heat AWAY from the engine as possible. Coolant that is at 196 is 16 degrees hotter than coolant that is at 180...which means it is removing from the engine and transporting an additional 16 degrees of heat to the radiator over a 180 degree thermostat. I know many will argue this point, is true.

2) fan shroud and fan sizes and compatibility with each other is another huge issue that many just plain don't understand and get wrong. The fan blades must be within 1/2" diameter of the fan shroud opening, and the blades must be sticking out of the back of the shroud about a 1/2" or so. If the fan diameter is too small for the shroud opening or the blades are too far inside the shroud, you will get near-zero air-flow through the radiator at idle...when most overheating occurs in hot-rods.

My 429 runs about 400 horse, and never overheats even during parade-duty. It uses a correctly-sized stock cooling system. No aluminum radiator.

My Torino's 460 (525 Horse) also runs cool, mostly because of a correctly sized radiator/fan shroud combo (although it does have electric fans in front to help out)
Thanks! That's all making sense. One step I didn't include in the first post was that I also pulled the block drain plugs. The car was mostly level when I did this. My driveway comes downhill until you get 5' from the garage. Then it levels out.

I wasn't having this problem before. The only reason I did any work was there is zero history on this car other than it sat for a few years and before that was supposidly a daily driver of 5 miles roundtrip. I'm just changing everything for TLC purposes.

I'm leaning down the path that I've got too much water in the system. So draining and reengaging is on the list. One of the pieces that didn't come with the car was a fan shroud. It's on my to buy and do list. Bigger fish to fry first. Id also like to get a new radiator cap. The one i have works but its pretty weathered on the top side. I'm almost half tempted to go back to the original, recommended thermostat as well instead of the 180. It's only been on this one for about 30 miles.

There are some pretty big gaps between cold and hot on newer cars for an overflow tank. Does everyone pretty much use the $55 stainless steel cylinder? I'm not looking for a concours car. I'm looking for a runs great car. Anyone use a $15 plastic tank? If so, how did you mount it?

Thanks again for all the inputs!
The type of recovery tank you install is entirely your preference. I installed this one from Jegs because it's more subtle in appearance. I also purchased a mounting bracket to go with it.

Apparently it's popular because it seems to be out of stock at this time.

They need to be installed at close to the height of the top of the radiator to help coolant travel back from the tank into the radiator as the coolant cools down.

Not sure what you mean by "too much water" in the system. The coolant only adds a couple extra degrees of cooling ability over straight water...its the additives in coolant that help with the other necessities: anti-corossion, water pump lubrication, electrolosys-prevention, etc...
I was referencing 1969 Mach1's post that I don't have the standard 50/50 mix.
Coolant is 2x heavier than takes more energy to move it through the cooling system, energy that is not making it to your wheels.
The standard 50/50 mix is just a generic country-wide mix that covers the widest range of temperatures. Less coolant will affect your cold-weather protection much more than hot-weather protection.
If you live in the southern US, a 25% coolant ratio is adequate, even if left out on the coldest night.
Since my car is kept in a garage in Florida, I have no issues with freezing to worry about. I run distilled water, about 16 ounces of coolant, a bottle of water pump lube/additives and 2 bottles of Water Wetter.
He could be refering to filling up the 'expansion gap'. Provided you use a cap with the secondary rubber seal your coolant will suck back no problems even if the o'flow coolant level is 12" below the radiator top. Both level is, of course, much better.
The amount pumped out should not effect cooling if you have no tank - the system was designed without it. IMO it is more important to keep air out with the expansion system rather than 100ml of coolant in.
The OP was more concerned with coolant being expelled (normal) rather than overheating problems. It is only that he kept topping up the system that he kept 'loosing' coolant.

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