Should both cooling system caps be pressurized ?
#7
Originally Posted by iluvmy3rdgen
Yeah, only use one pressurized cap, using two increases the amount of pressure in the system, it will have to create more room for expansion.
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#8
You mean no pressure on the overflow tank?
Don't you have to use pressure cap on the filler neck?
The stock filler neck cap is pressurized and so is the stock AST cap.
Am I missing something? Doh! I guess I better check mine...
Don't you have to use pressure cap on the filler neck?
The stock filler neck cap is pressurized and so is the stock AST cap.
Am I missing something? Doh! I guess I better check mine...
Last edited by jupiter; 01-25-05 at 10:02 PM.
#9
Originally Posted by jupiter
You mean no pressure on the overflow tank?
Don't you have to use pressure cap on the filler neck?
The stock filler neck cap is pressurized and so is the stock AST cap.
Am I missing something?
Don't you have to use pressure cap on the filler neck?
The stock filler neck cap is pressurized and so is the stock AST cap.
Am I missing something?
Quite simply, are they both necessary?
#11
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Originally Posted by Jesuscookies
I have a pressurized cap on the filler neck, and a pressurized cap on my aftermarket AST.
Quite simply, are they both necessary?
Quite simply, are they both necessary?
#12
~17 MPG
iTrader: (2)
It seems like a few people here don't quite understand how radiator caps work. A cap with a spring in it is a pressure RELIEF cap. A 13lb cap will release pressure if it gets above 13psi. Using two pressure caps makes no sense, it's redundant and there is no need for it.
You might have problems somehow, if they both relieved too much pressure at once, pressure might suddenly drop from 14 >>9 psi, reducing the boiling point quickly and allowing the coolant to vaporize. I'm not saying that this will definitely happen, but it's a worst case scenario that I can think of.
http://auto.howstuffworks.com/cooling-system7.htm
-s-
You might have problems somehow, if they both relieved too much pressure at once, pressure might suddenly drop from 14 >>9 psi, reducing the boiling point quickly and allowing the coolant to vaporize. I'm not saying that this will definitely happen, but it's a worst case scenario that I can think of.
http://auto.howstuffworks.com/cooling-system7.htm
-s-
#13
Racecar - Formula 2000
Just to eliminate confusion:
In the stock setup, the filler cap SEALS TO THE ATMOSPHERE, but lets coolant flow freely (at internal coolant pressure) to and from the AST. The AST cap is a pressure relief (0.9 BAR) and coolant return cap. This vents to the overflow tank when internal pressure exceeds 0.9 BAR, and draws coolant back to the engine when the pressure in the engine drops below atmospheric (vacuum) as it cools and the coolant contracts.
In the stock setup, the filler cap SEALS TO THE ATMOSPHERE, but lets coolant flow freely (at internal coolant pressure) to and from the AST. The AST cap is a pressure relief (0.9 BAR) and coolant return cap. This vents to the overflow tank when internal pressure exceeds 0.9 BAR, and draws coolant back to the engine when the pressure in the engine drops below atmospheric (vacuum) as it cools and the coolant contracts.
#14
Rotary Enthusiast
just to add confusion ...
With stock set-up (ast), any pressure regulating cap can be used on the filler neck, since only the ast cap rating will control system pressure.
But, the stock filler cap (no internal spring) is designed to seal 15+ psi at the rim of the neck. Typical regulating caps (with internal spring) don't normally see pressure at that location, only slight vacuum. The pressure is controlled by the lower rubber washer, below the spring.
So ... although a typical regulating cap (with spring) will work at the filller neck, it is the stock cap (no spring) that is designed for that location, and is less likely to leak.
With stock set-up (ast), any pressure regulating cap can be used on the filler neck, since only the ast cap rating will control system pressure.
But, the stock filler cap (no internal spring) is designed to seal 15+ psi at the rim of the neck. Typical regulating caps (with internal spring) don't normally see pressure at that location, only slight vacuum. The pressure is controlled by the lower rubber washer, below the spring.
So ... although a typical regulating cap (with spring) will work at the filller neck, it is the stock cap (no spring) that is designed for that location, and is less likely to leak.
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