Cooling System

[Joe C.]

Re: Cooling System

How would air (if any) in the rad vent to the supply tank at less than blow off pressure?

There shouldn't be any air in the rad once the system is filled and bled unless the head gasket is leaking or he has a cracked block or head. To ensure against the slight chance that air would somehow get into the rad, the cheap, generic "closed system" cap which I suggested Leif install can be modified by several means which will disable the lower seal, but maintain the upper seal and make that cap behave like an ordinary jar lid (seal to atmosphere but keep the 1/4" nipple always open). This isn't the solution that I suggested in an earlier post. The current setup provides operability as an open system, will all the inherent consequences, such as "puking" out the overflow hose with resultant need to monitor coolant level.

Reread my earlier post which recommends how to convert his system to a care-free/trouble-free closed system.

[Leif A.]

Re: Cooling System

The cap that is currently blowing off, Joe, is the one at the supply tank thru the 1/4" nipple open to the atmosphere. Before spending the big bucks on a new DeWitts, I'm going to try your suggestion and put a generic 18# closed system radiator cap on the radiator itself and keep the RC-26 15# on the supply tank and see how that goes.Guys, it sure helps my thought process having so many 'vette brains working on my problem...thanks so much.

[Michael W.]

Re: Cooling System

The cap that is currently blowing off, Joe, is the one at the supply tank thru the 1/4" nipple open to the atmosphere. Before spending the big bucks on a new DeWitts, I'm going to try your suggestion and put a generic 18# closed system radiator cap on the radiator itself and keep the RC-26 15# on the supply tank and see how that goes.Guys, it sure helps my thought process having so many 'vette brains working on my problem...thanks so much.

I think you'd want a lower pressure cap on the rad than the supply tank to ensure that it vents air to the supply tank.

[Duke W.]

Re: Cooling System

The cap that is currently blowing off, Joe, is the one at the supply tank thru the 1/4" nipple open to the atmosphere. Before spending the big bucks on a new DeWitts, I'm going to try your suggestion and put a generic 18# closed system radiator cap on the radiator itself and keep the RC-26 15# on the supply tank and see how that goes.Guys, it sure helps my thought process having so many 'vette brains working on my problem...thanks so much.

The connection from the radiator to the expansion tank needs to be open all the time so vapor can vent to the expansion tank. The way it's currently configured that passage is effectively blocked by the radiator pressure cap, and there's no effective way to purge vapor bubbles from the liquid.

What should work so the system performs as designed would be to cut off the the pressure relief portion of the cap on the radiator. Then reinstall the cap with a good gasket, which should seal the opening and prevent seepage, and the radiator is now properly vented to the expansion tank.

Once that's done never remove the radiator cap again. Do all coolant checks and additions through the expansion tank cap.

Some increase in temperature with extensive idling is normal, especially if ambient is over 80F. If the temperature does not exceed about 230 in heavy traffic with the AC on at 100F ambient then the radiator is probably sufficient, but has less margin than the OE type radiator.

A 50/50 blend of ethylene glycol antifreeze and water boils at 265F with a 15 psi cap. I consider the normal operating temperature range of these systems to be 180-230F. At 230F you still have 35 degrees boilover margin, however you should only see 230F in extreme conditions like traffic jams with the AC on at 100F or more ambient.

Duke

[Joe C.]

Re: Cooling System

The connection from the radiator to the expansion tank needs to be open all the time so vapor can vent to the expansion tank. The way it's currently configured that passage is effectively blocked by the radiator pressure cap, and there's no effective way to purge vapor bubbles from the liquid.

What should work so the system performs as designed would be to cut off the the pressure relief portion of the cap on the radiator. Then reinstall the cap with a good gasket, which should seal the opening and prevent seepage, and the radiator is now properly vented to the expansion tank.

Once that's done never remove the radiator cap again. Do all coolant checks and additions through the expansion tank cap.

Some increase in temperature with extensive idling is normal, especially if ambient is over 80F. If the temperature does not exceed about 230 in heavy traffic with the AC on at 100F ambient then the radiator is probably sufficient, but has less margin than the OE type radiator.

A 50/50 blend of ethylene glycol antifreeze and water boils at 265F with a 15 psi cap. I consider the normal operating temperature range of these systems to be 180-230F. At 230F you still have 35 degrees boilover margin, however you should only see 230F in extreme conditions like traffic jams with the AC on at 100F or more ambient.

Duke

Hey, yo! Read post #46.