Coolant system not under pressure - JeepForum.com

 
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post #1 of 8 Old 01-02-2010, 06:44 PM Thread Starter
mmerlina
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Coolant system not under pressure

Hey what happens when a coolant system is not under pressure? I have one of those radiator caps with that safety air pressure release tab on the top of it.. every now and then I'll pop my hood and see it flipped up..

I wasn't loosing any coolant out of it, just air pressure I'm guessing.. what would cause that to flip up and what could happen if the system isn't pressurized?


Mike

1986 Jeep CJ7 (photos)
Remanufactured 258, ARB lockers front & rear, 4.10 Yukon gears, 35x12.5" Super Swamper SSR's, Motorcraft 2100, 4.5" Rubicon Express Extreme-Duty lift, York 210 OBA, Big Daddy steering, Tatton rear CV driveshaft, Herculined interior, TJ flares, lots of body & upholstery work
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post #2 of 8 Old 01-02-2010, 07:55 PM
scooter
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Water boils at 212 at seal level,pressurizing the system raises the boiling point x degrees every PSI the pressure is raised in the system. There is a formula/value I dont recall. The other side is air in the system,not long ago there were no overflow bottles etc,the system pressurized and blew out what it could when hot,then as it cooled it sucked air back in and you had a system with air in it. The idea with a closed system is to eliminate this, so in a nut shell go break the bank and buy a new cap, it dosent have to be one with a lever as long at its the same pressure value.
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post #3 of 8 Old 01-02-2010, 10:16 PM
wrongway92407
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buy a new cap, w/o the lever

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post #4 of 8 Old 01-02-2010, 11:27 PM Thread Starter
mmerlina
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Hmm okay, yeah I'll get a new cap without one of those damn things.. I don't even know how it ended up on there to be honest with you.

What happens to a standard cap when/if the pressure exceeds the rating of the cap? I see on quadratec it looks like a stock cap for a CJ is 16 pounds.. but I see other caps at 13. Not like I'd experiment with it or anything, just curious.

Mike

1986 Jeep CJ7 (photos)
Remanufactured 258, ARB lockers front & rear, 4.10 Yukon gears, 35x12.5" Super Swamper SSR's, Motorcraft 2100, 4.5" Rubicon Express Extreme-Duty lift, York 210 OBA, Big Daddy steering, Tatton rear CV driveshaft, Herculined interior, TJ flares, lots of body & upholstery work
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post #5 of 8 Old 01-03-2010, 09:14 AM
CJunk
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If you have an overflow bottle and a nipple on the radiator, (under the cap) you will be fine. Dont know the info on the cap rating though.
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post #6 of 8 Old 01-03-2010, 09:30 AM
scooter
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If the cap does not meet the requirements of the cooling system/vehicle its going on it may blow radiator seams or otherwise,some run a lower rating cap on old systems to prevent this. Best bet is the correct cap and a overflow bottle set up correctly. If done right the cap will allow coolant out into the bottle when hot,then later when things cool and contract the coolant will actyally be sucked back into the systen thru the cap which acts like a check valve basically. If you have no recovery bottle it will as mentioned blow out some coolant leaving a void of air in the radiator which for one decreases your cooling capacity and allows air into the system which will begin to oxidize things.
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post #7 of 8 Old 01-03-2010, 10:44 AM
Cutlass327
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I would get the stock rated cap. If your radiator is weak and starts leaking, then it is meant to fail - no use "Band-aiding" a weak part with a lower PSI cap. The stock rated cap will help to run at proper temps, so that when you have issues with cooling or heat, then we will be able to help diagnose then since it is set up the way it is supposed to be.

Rick

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post #8 of 8 Old 01-03-2010, 11:14 AM Thread Starter
mmerlina
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Yep I'm going to get a stock cap.. I'd rather not cover up problems by lowering the pressure. I believe my radiator is in pretty decent condition, I've seen it from most angles and I've never seen anything to be concerned about. *knock on wood*

Mike

1986 Jeep CJ7 (photos)
Remanufactured 258, ARB lockers front & rear, 4.10 Yukon gears, 35x12.5" Super Swamper SSR's, Motorcraft 2100, 4.5" Rubicon Express Extreme-Duty lift, York 210 OBA, Big Daddy steering, Tatton rear CV driveshaft, Herculined interior, TJ flares, lots of body & upholstery work
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