409 - Radiator overflow

#1
All,

New owner here...The only two times I've taken it out for a nice joyride, I get back to my garage and the overflow tube leaks what appears to be 6 - 8 ounces of coolant. It is now below the "register" or whatever it's called (located like one inch below the cap).

I just bought the car, and the seller basically told me "no worries" and that it will do this until it reaches a level it feels good at. Once it stops leaking like that, it will be fine.

Do I need a higher pressure-rated cap?

PS - No indications of overheating so far - Thoughts?
 

Junky

Well Known Member
#5
How can we tell you if you need a "higher" cap, without knowing what the cap that you have is. It could be that there is air trapped in the engine, or it could be a blown head gasket. The only way to know exactly what is going on is to use a tool that will pressurize the cooling system and show if there is an internal leak into the combustion chamber. I am not trying to alarm you, just pointing out that you need to do some diagnostic evaluation, prior to saying

the seller basically told me "no worries" and that it will do this until it reaches a level it feels good at. Once it stops leaking like that, it will be fine.
It is always better to know exactly what the problem is before you just assume that it is x, y, or z.........
 

IMBVSUR?

Well Known Member
Supporting Member 2
#7
I guess there could always be lots of issues. Try leaving about 3/4 below the cap and running a 15lbs pressure cap and see how it does temperature wise.
 

Junky

Well Known Member
#8
Think about how much the "water" expands from ambient temperature to 212 degrees, without a radiator cap. Then add 3 degrees for every pound of the pressure cap, and for the purpose of this exercise, we will say that he is using a 10 pound cap. Add 30 degrees to the boiling point of 212 degrees, and that engine is now equivalent to a pressure cooker at 242 degrees. Now, lets look at how much expansion is going on in the "pressure cooker"....... Water is at its maximum density at 4 degrees Celsius (39.2), and its volume (and thus pressure in a closed container) increases with temperature according to its coefficient of expansion and the degrees of temperature rise, and keep in mind that liquids are not compressible. In short, if the temperature and pressure rise to a certain point, that there is no room left in the radiator, then it has to spill out the radiator overflow. The cap is designed to "open" under pressure, otherwise the radiator would blow out.
Sheldon
 

427John

Well Known Member
#10
Junky,while in your post you were talking about the properties of water and are absolutely right that water is not compressible but some liquids are to a certain extent including lots of oils,that is why it is so important to follow manufacturers specifications on oils for hydraulic systems because they tune the damping of the system based on the compressibility of the oil they specify.Its the incompressibility of of water that makes it the choice of hydraulic systems that require a precise and predictable response.
 

Carmine

Well Known Member
Supporting Member 7
#11
I had a car that did the same thing. After a ride and sitting, it would puke out antifreeze. I'd refill it and the same thing would happen again. This went on several times until I was told that the radiator/system would seek the level it is comfortable with. This level is about 1.5 inches down from the top of the tank and just covers the rows of internal tubes. Left it there. Doesn't overheat or run hot, Carmine.
 

Junky

Well Known Member
#12
Junky,while in your post you were talking about the properties of water and are absolutely right that water is not compressible but some liquids are to a certain extent including lots of oils,that is why it is so important to follow manufacturers specifications on oils for hydraulic systems because they tune the damping of the system based on the compressibility of the oil they specify.Its the incompressibility of of water that makes it the choice of hydraulic systems that require a precise and predictable response.
You are correct, and when I was talking to Sheldon, and he was giving me his dissertation on the subject, I knew better than to interrupt or correct anything that he had said. Raj, Leonard, and Howard were all pushing me to challenge him on his theory, but Amy warned me that both she and I would pay the price if I did. She for having to live with him, and me for being his friend. Thanks for your comment about compressibility of certain liquids. When I see Sheldon next time, I will tell him exactly what you have said, and that way he can be angry with you, but not me.

Junk
 

427John

Well Known Member
#13
You are correct, and when I was talking to Sheldon, and he was giving me his dissertation on the subject, I knew better than to interrupt or correct anything that he had said. Raj, Leonard, and Howard were all pushing me to challenge him on his theory, but Amy warned me that both she and I would pay the price if I did. She for having to live with him, and me for being his friend. Thanks for your comment about compressibility of certain liquids. When I see Sheldon next time, I will tell him exactly what you have said, and that way he can be angry with you, but not me.

Junk
Your welcome Jackass
 

427John

Well Known Member
#15
Thats me when I'm going to be dick on the internet I own it,not like the little snatches like you that make their condescending or patronizing statements and veiled insults which your posts are full of.
 
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