From OP: Interpretation ?

Hello,

Thanks all for help.
Much appreciated.

So, my understanding from the replies is that even if it were a
defective radiator cap, any coolant that the cap releases, due to its
being defective, would (probably) just end up in that small plastic
overflow jug ?

(I think it's called an overflow jug ?)

a. So, like was mentioned, the level in that jug should therefore Not be
getting lower as the total amount of coolant is the same (none lost to
the outside) ? Actually, perhaps even higher as it accepts some from the
radiator ?

b. Or, is it that some might still be lost to the outside due to a bad
cap, and the radiator, when the car starts out, is sucking in some
coolant from the jug ? Therefore, a lower level in the jug ?

Am I interpreting this correctly ?

Thanks,
Bob

"Bob" > wrote in message
...
> Hello,
>
> Thanks all for help.
> Much appreciated.
>
> So, my understanding from the replies is that even if it were a defective
> radiator cap, any coolant that the cap releases, due to its being
> defective, would (probably) just end up in that small plastic overflow jug
> ?

No, that is not correct. It all depends upon whether that stand
alone tank is an expansion or an overflow tank The former is
pressurized, the latter is not. Read this:
http://www.custompistols.com/cars/articles/overflow.htm

> (I think it's called an overflow jug ?)
>
> a. So, like was mentioned, the level in that jug should therefore Not be
> getting lower as the total amount of coolant is the same (none lost to the
> outside) ? Actually, perhaps even higher as it accepts some from the
> radiator ?
>
> b. Or, is it that some might still be lost to the outside due to a bad
> cap, and the radiator, when the car starts out, is sucking in some coolant
> from the jug ? Therefore, a lower level in the jug ?
>
> Am I interpreting this correctly ?
>
> Thanks,
> Bob

Gene wrote:
> "Bob" > wrote in message
> ...
>> Hello,
>>
>> Thanks all for help.
>> Much appreciated.
>>
>> So, my understanding from the replies is that even if it were a defective
>> radiator cap, any coolant that the cap releases, due to its being
>> defective, would (probably) just end up in that small plastic overflow jug
>> ?
>
> No, that is not correct. It all depends upon whether that stand
> alone tank is an expansion or an overflow tank The former is
> pressurized, the latter is not. Read this:
> http://www.custompistols.com/cars/articles/overflow.htm

The OP stated that the vehicle is a 2005 Honda Accord. That vehicle has
a common overflow tank. Not a pressurized tank.



>
>> (I think it's called an overflow jug ?)
>>
>> a. So, like was mentioned, the level in that jug should therefore Not be
>> getting lower as the total amount of coolant is the same (none lost to the
>> outside) ? Actually, perhaps even higher as it accepts some from the
>> radiator ?

Correct. This is a non pressure tank unit. Normal operation is:

Cold start with a full system and full radiator (IE you topped it off)
As the engine warms up the coolant expands until it reaches the pressure
the cap is rated at. When it hits that pressure the valve in the lower
section of the cap gets pushed up and the coolant goes through the neck
of the radiator into the overflow tube and into the
reserve/overflow/capture tank. (This is different than earlier vehicles
that just dumped the excess onto the ground). Now the coolant gets to a
point where the pressure in the system stabilizes as the temperature
stabilizes. At that point the overflow should be checked. It should be
on the full hot mark. If not you top it up.

Now as the engine cools off the coolant starts to contract as well. This
causes the system to form a vacuum. The vacuum will do one of two
things. On some vehicles it will simply draw air into the radiator
through the valve in the center of the cap. OR on many vehicles the
vacuum will draw coolant out of the overflow bottle and keeps the system
from drawing in air (this is common on most newer vehicles because air
can cause problems when mixed into the coolant)



>>
>> b. Or, is it that some might still be lost to the outside due to a bad
>> cap, and the radiator, when the car starts out, is sucking in some coolant
>> from the jug ? Therefore, a lower level in the jug ?

The accord uses a gravity drop into the overflow. Unless the tube is
blocked the coolant should go into the bottle either way.


>>
>> Am I interpreting this correctly ?
>>
>> Thanks,
>> Bob
>

"Steve W." > wrote in message
...
> Gene wrote:
>> "Bob" > wrote in message
>> ...
>>> Hello,
>>>
>>> Thanks all for help.
>>> Much appreciated.
>>>
>>> So, my understanding from the replies is that even if it were a
>>> defective
>>> radiator cap, any coolant that the cap releases, due to its being
>>> defective, would (probably) just end up in that small plastic overflow
>>> jug
>>> ?
>>
>> No, that is not correct. It all depends upon whether that stand
>> alone tank is an expansion or an overflow tank The former is
>> pressurized, the latter is not. Read this:
>> http://www.custompistols.com/cars/articles/overflow.htm
>
> The OP stated that the vehicle is a 2005 Honda Accord. That vehicle has a
> common overflow tank. Not a pressurized tank.

Which makes no aspect of my above comment incorrect.
Before even delving into the subject of an exterior tank, I
clearly stated "I'm not certain as to the application's system
but he clearly stated radiator cap, not coolant recovery tank".
And in any case, if he's referring to a radiator cap replacement,
that cap is either on the radiator itself, or an external expansion
tank. There is nothing on a strictly overflow (not expansion)
tank that could remotely be confused with a radiator style cap.

>>> (I think it's called an overflow jug ?)
>>>
>>> a. So, like was mentioned, the level in that jug should therefore Not be
>>> getting lower as the total amount of coolant is the same (none lost to
>>> the
>>> outside) ? Actually, perhaps even higher as it accepts some from the
>>> radiator ?
>
> Correct. This is a non pressure tank unit. Normal operation is:
>
> Cold start with a full system and full radiator (IE you topped it off)
> As the engine warms up the coolant expands until it reaches the pressure
> the cap is rated at. When it hits that pressure the valve in the lower
> section of the cap gets pushed up and the coolant goes through the neck of
> the radiator into the overflow tube and into the reserve/overflow/capture
> tank. (This is different than earlier vehicles that just dumped the excess
> onto the ground). Now the coolant gets to a point where the pressure in
> the system stabilizes as the temperature stabilizes. At that point the
> overflow should be checked. It should be on the full hot mark. If not you
> top it up.
>
> Now as the engine cools off the coolant starts to contract as well. This
> causes the system to form a vacuum. The vacuum will do one of two things.
> On some vehicles it will simply draw air into the radiator through the
> valve in the center of the cap. OR on many vehicles the vacuum will draw
> coolant out of the overflow bottle and keeps the system from drawing in
> air (this is common on most newer vehicles because air can cause problems
> when mixed into the coolant)

Or if there's a leak in the system, what ever medium (e.g., air)
is adjacent to that leak may be drawn into the cooling system,
possibly providing an erroneous indication (from the appearance
of the level in the overflow tank) that the coolant level in the
system is nominal, despite the fact that it can now be low.

>>> b. Or, is it that some might still be lost to the outside due to a bad
>>> cap, and the radiator, when the car starts out, is sucking in some
>>> coolant
>>> from the jug ? Therefore, a lower level in the jug ?
>
> The accord uses a gravity drop into the overflow. Unless the tube is
> blocked the coolant should go into the bottle either way.

Fluid forced out of the radiator by expansion of the coolant
is fed from the cap area, through the overflow line, and into
the bottom of the partially filled OT, thereby always ensuring
that the system remains free of air. Gravity maintains fluid at
the bottom of the tank, but neither the filling of the coolant
into the tank (pushed out of the radiator by fluid expansion)
nor its draining out (pushed into the radiator by air pressure
as a result of a partial vacuum created by fluid contraction)
is "gravity fed", per se, unless of course one considers that
rho*g*h is a representation of atmospheric pressure.

>>> Am I interpreting this correctly ?
>>>
>>> Thanks,
>>> Bob

Bob wrote:
>
> Hello,
>
> Thanks all for help.
> Much appreciated.
>
> So, my understanding from the replies is that even if it were a
> defective radiator cap, any coolant that the cap releases, due to its
> being defective, would (probably) just end up in that small plastic
> overflow jug ?
>

Depends what "defective radiator cap" means.

The cap has several functions. It acts like a pressure regulator
that maintains the cooling system design pressure. It also acts
to divert excess fluid and pressure into the overflow and allow
the fluid to return when the pressure drops below normal
atmosphere pressure. There are several gaskets (rubber seals),
valves and springs which could be defective.

It's possible the cap itself is allowing fluid to leak
out of the system when you aren't looking. Or if the system
is running with too high or too low pressure that also could
result in leakage that you don't notice.

The easiest way to check the cap is put a new one on and
see if anything changes.

-jim



> (I think it's called an overflow jug ?)
>
> a. So, like was mentioned, the level in that jug should therefore Not be
> getting lower as the total amount of coolant is the same (none lost to
> the outside) ? Actually, perhaps even higher as it accepts some from the
> radiator ?
>
> b. Or, is it that some might still be lost to the outside due to a bad
> cap, and the radiator, when the car starts out, is sucking in some
> coolant from the jug ? Therefore, a lower level in the jug ?
>
> Am I interpreting this correctly ?
>
> Thanks,
> Bob