healeys
[Top] [All Lists]

Re: [Healeys] Overheating Healey (closed system)

To: "'Eric \(Rick\) Wilkins'" <e-wilkins@cox.net>
Subject: Re: [Healeys] Overheating Healey (closed system)
From: "Herbert Miller" <hgmiller3@qwest.net>
Date: Tue, 27 Jul 2010 08:03:39 -0500
All modern cooling systems are closed. It does not matter where the pressure
cap is located, (radiator or catch tank) the effect is the same, as to
pressure in the system. 
Herb Miller
-----Original Message-----
From: healeys-bounces@autox.team.net [mailto:healeys-bounces@autox.team.net]
On Behalf Of Eric (Rick) Wilkins
Sent: Monday, July 26, 2010 10:42 PM
Cc: healeys
Subject: Re: [Healeys] Overheating Healey (closed system)

As coolant gets hot, it expands.  Since the cooling system is sealed,  
this expansion causes an increase in pressure in the cooling system,  
which is normal and part of the design.  When coolant is under  
pressure, the temperature where the liquid begins to boil is  
considerably higher.  This pressure, coupled with the higher boiling  
point of ethylene glycol, allows the coolant to safely reach  
temperatures in excess of 250 degrees.

The radiator pressure cap is a simple device that will maintain  
pressure in the cooling system up to a certain point.  If the pressure  
builds up higher than the set pressure point, there is a spring loaded  
valve, calibrated to the correct Pounds per Square Inch (psi), to  
release the pressure.

When the cooling system pressure reaches the point where the cap needs  
to release this excess pressure, a small amount of coolant is bled  
off.  It could happen during stop and go traffic on an extremely hot  
day, or if the cooling system is malfunctioning.  If it does release  
pressure under these conditions, there is a system in place to capture  
the released coolant and store it in a plastic tank that is usually  
not pressurized.  Since there is now less coolant in the system, as  
the engine cools down a partial vacuum is formed.  The radiator cap on  
these closed systems has a secondary valve to allow the vacuum in the  
cooling system to draw the coolant back into the radiator from the  
reserve tank (like pulling the plunger back on a hypodermic needle)   
There are usually markings on the side of the plastic tank marked Full- 
Cold, and Full Hot.  When the engine is at normal operating  
temperature, the coolant in the translucent reserve tank should be up  
to the Full-Hot line.  After the engine has been sitting for several  
hours and is cold to the touch, the coolant should be at the Full-Cold  
line.


On Jul 26, 2010, at 7:57 PM, Bob Spidell wrote:

> re: "A closed system with a return tank raises the boiling temp"
>
> How?
>
>
> bs
_______________________________________________
Healeys@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation  $12.75
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe/Manage:
http://autox.team.net/mailman/options/healeys/hgmiller3@qwest.net
_______________________________________________
Healeys@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation  $12.75
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums

<Prev in Thread] Current Thread [Next in Thread>