The standard 6cyl radiator cap for a Lh is 103kpa (15psi) as stated in the manual.
The bloke at the auto shop sold me a 135kpa cap.
Wondering how dangerous it would be running the 135kpa cap on a standard sized 6 cyl radiator?
Im guessing if it overheats its not gonna be good, possibly causing a crack/leak in the radiator?
-matt
Radiator cap pressure rating
Started by
_just_matt_
, Oct 01 2006 07:43 PM
8 replies to this topic
#2
_devilsadvocate_
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Posted 01 October 2006 - 08:35 PM
Take it back, you are going to subject you cooling system to near this pressure(depending how full the radiator is or always if running a recovery system), 20psi every time you run it, not just when it gets hot. In the short term nothing may happen, but you run the risk of reducing the life of radiator, hoses, head gasket, water pump gasket and heater core. All these components fail sooner or later from 15psi rad caps(it keeps mechanics busy).........don�t exacerbate it. To emphasise this point, we have a EA falcon with a small external leak on the head gasket. The radiator/fan combo on this car really works well and even in 40+ conditions it doesnt move of thermostat temp, basically it doesnt need pressurisation......we just partially secure the screw down rad cap and it doesnt lose a drop, but otherwise would lose a litre per hour.
15psi systems were designed for holdens with straight water as the coolant in mind and to give a theoretical 125C temp before the water boils...... 1.6deg C for each psi increase.
Id recommend running some glycol so this temp could be achieved at a lower pressure ie 12 or 13 psi, or even 7-9psi as run in earlier holdens, for the sake of everything lasting longer. Yes the specific heat capacity of glycol is lower than water, but in the small concentrations req to elevate the boiling point ~!5%, the difference is not huge.
The coolant recovery type caps arent available in less than 13psi, which I run on my car. Possibly there may be some prob with the water pump blowing a low pressure cap 7-9psi at high rpm.......but could suck and see on this one.
The trend for high temperature engines of the future is to run high temp coolants, ie boiling points 200C+ and not run any pressurisation at all.
15psi systems were designed for holdens with straight water as the coolant in mind and to give a theoretical 125C temp before the water boils...... 1.6deg C for each psi increase.
Id recommend running some glycol so this temp could be achieved at a lower pressure ie 12 or 13 psi, or even 7-9psi as run in earlier holdens, for the sake of everything lasting longer. Yes the specific heat capacity of glycol is lower than water, but in the small concentrations req to elevate the boiling point ~!5%, the difference is not huge.
The coolant recovery type caps arent available in less than 13psi, which I run on my car. Possibly there may be some prob with the water pump blowing a low pressure cap 7-9psi at high rpm.......but could suck and see on this one.
The trend for high temperature engines of the future is to run high temp coolants, ie boiling points 200C+ and not run any pressurisation at all.
Edited by devilsadvocate, 01 October 2006 - 08:46 PM.
#3
_just_matt_
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Posted 01 October 2006 - 11:40 PM
Okay, so I understand SOME of your post 
Its not running a coolant recovery system at the moment but hopefully later it will.
My dad put two tins of this Castrol rust preventer/coolant (fluro yellow stuff) in the radiator. I dont know if it was/contains glycol but will find out, and ill also find out how much of it went in.
So your saying a 135kpa cap is too much?
Do I want to get a standard (15psi) rated one?
-matt
Its not running a coolant recovery system at the moment but hopefully later it will.
My dad put two tins of this Castrol rust preventer/coolant (fluro yellow stuff) in the radiator. I dont know if it was/contains glycol but will find out, and ill also find out how much of it went in.
So your saying a 135kpa cap is too much?
Do I want to get a standard (15psi) rated one?
-matt
#4
rodomo
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Posted 02 October 2006 - 12:02 AM
Yes. Get the right cap. Heater core may suffer and anythong else that is as old as the car.
#5
_devilsadvocate_
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Posted 02 October 2006 - 12:42 AM
If you are going to run a coolant recovery system later, might as well get the cap now and pay only once...........if you have some glycol in there get the 13psi one.
#6
TerrA LX
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Posted 02 October 2006 - 01:46 AM
the castrol type u refer to is only inhibitor, no glycol.
#7
_just_matt_
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Posted 02 October 2006 - 06:56 PM
ALX76, I looked at the tin of Castrol stuff and this is what it says.
Radiator Corrosion Inhibitor
Contains: Boron 2.2% w/w
Ethylene Glycol 45% w/w with 10mg/kg of Denatonium Benoate
2 tins of this went in, this is what is reccomended for 6 and 8 cyl motors as stated on the tin.
*Edit* fixed spellin errors
Radiator Corrosion Inhibitor
Contains: Boron 2.2% w/w
Ethylene Glycol 45% w/w with 10mg/kg of Denatonium Benoate
2 tins of this went in, this is what is reccomended for 6 and 8 cyl motors as stated on the tin.
*Edit* fixed spellin errors
Edited by just_matt, 02 October 2006 - 07:06 PM.
#8
TerrA LX
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Posted 02 October 2006 - 07:08 PM
^ i stand corrected, not the lil white castrol tins i thought.
#9
rodomo
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Posted 02 October 2006 - 11:46 PM
I always recommend that stuff unless you live in the snow country.
But then I'm from Melb. No snow, no big heat.
But then I'm from Melb. No snow, no big heat.
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