[57vette]

I'm waiting on a billet tubular expansion tank that I'm going to connect to the overflow outlet on the radiator neck. Just wondering if the coolant level would need to be higher in the radiator with a expansion tank? Right now its at about 4" below the neck. I used a fitted funnel to try and burp the engine, got lots of bubbles then it seemed to settle down. I ran out of coolant so I'll pick up another gallon just to have some handy, but should I get the coolant level say... 2" below the neck?

Mike

 

[bhodgdon400]

with the overflow tank, just fill radiator to brim and it will puke out what it doesn't want. about 2-4" below neck is normal

 

[chicoman]

Just make sure when filling to brim that the expansion tank is large enough to handle the overflow.

 

[DOUG G]

I always go about 1" from the neck...room for expansion and room for over-flow.

 

[SoCal805]

I fill mine to the neck and let the radiator/coolant recovery tank do its thing

if you are installing a "coolant recovery tank" than you need to have a 1"-2" of coolant in that tank so the pick-up part of the hose/tube than goes in it will be submerged so when the heated coolant expands and overflows into it the suction created by the cooling radiator will draw it back into the radiator

when doing a radiator flush or installing some new component of the cooling system (WP, radiator) it can take a heat/cool cycle or two for the cooling system to purge any air so you will need to "top off" the radiator after that

 

[57vette]

I fill mine to the neck and let the radiator/coolant recovery tank do its thing

if you are installing a "coolant recovery tank" than you need to have a 1"-2" of coolant in that tank so the pick-up part of the hose/tube than goes in it will be submerged so when the heated coolant expands and overflows into it the suction created by the cooling radiator will draw it back into the radiator

when doing a radiator flush or installing some new component of the cooling system (WP, radiator) it can take a heat/cool cycle or two for the cooling system to purge any air so you will need to "top off" the radiator after that

Thanks... Its a 13" X 2" tank and I'm rigging it as a recovery tank. It has two (2) 7/16 20 NPT barbed hose fittings, one has a tube extending up near the top, the other I think is just open on the bottom.


Capacity is about 13 ounces, so when I get it installed I'll the 1"-2" you suggested and also burp the system one more time with the Funky Funnel gadget. When you said it could take a heat/cool cycle or two to purge the last bits of air... will it purge air into the recovery tank or should I just open the cap when it's cold?

Mike

 

[scblucam]

If you are changing the system you will need a new radiator cap so the fluid will be drawn back to the radiator when it cools.Radiator should be full. Expansion flows to the recovery tank and than is sucked back in when the radiator cools. Modern system vs ancient system.

 

[SoCal805]

Radiator Caps Explained

Radiator Caps Explained (coolcatcorp.com)

 

[LeeC]

Radiator Caps Explained

Radiator Caps Explained (coolcatcorp.com)

Any part numbers and brand of vented cap to use?

 

[57vette]

So once I install the expansion tank and plumb it, I'll need a cap like this?

I'm sure there are other brands... I have a billet cap cover on my regular 16# cap which is new... but I want the system to work the way SoCal described it.

Mike

 

[SoCal805]

one that says "closed system" on it. I use a AC Delco RC81

part# 25661994

 

[57vette]

Here's an interesting diagram showing what I think we're talking about.

Radiator caps aren't that expensive... I ordered the Delco you suggested. I've got the brand new one that came with the Cold Case radiator, but I don't know if its a vented one. And the one inside the billet housing... its probably a Dorman or Gates. I have to take it apart as the beauty cap just gets 3M double sided taped to the inside.

Mike

 

[SoCal805]

I've got the brand new one that came with the Cold Case radiator, but I don't know if its a vented one.

Mike

FWIW, Eric @ CC PM me saying the CC cap is a 16PSI vented cap...

 

[57vette]

I did order the Delco cap, I will compare it to the Cold Case cap. The cap I had on my old 4-core radiator has the billet cover on it. I don't recall the brand or model, but look at the difference in the springs. It looks like it has a vent hole but I'm not sure. I'm gonna use either the CC cap or the Delco to make sure its a vented cap. Expansion tank should be here in a couple of days, coming via USPS Priority which could take forever these days. Chris Cass had told me that #16 cap is fine with his radiators, and I've also read that #15 is normal for most older muscle cars. Go figure.-Mike

 

[SoCal805]

while CC (Eric) said the CC cap is for a closed (vented) system I just use the AC Delco RC33 (aka pink top) cap I had and it is 15 PSI. IMHO a CC radiator and a heater core are fine with 16 PSI

I did notice the CC cap did have a vent hole on one side but the RC33 has it on both sides but assume otherwise they function the same

With the recovery tank I see the coolant level in radiator stays about 1/2" below the fill neck vs about 2+" when it was just using a non-vented cap and coolant would just overflow to ground leaving the larger expansion space in the radiator. I notice no difference in operating temps between the closed and open systems. I did the coolant recovery because its needed at NHRA tracks to pass tech

 

[The Camaro Guy]

Inquiring old minds want to know. . . . .these cars were not designed for overflow tank and none of my cars overheat, even my 05 Vette does'nt use the OT. So my question is what is the point?

 

[scblucam]

Inquiring old minds want to know. . . . .these cars were not designed for overflow tank and none of my cars overheat, even my 05 Vette does'nt use the OT. So my question is what is the point?

My guess would be to keep Ethylene Glycol off the street.

 

[SoCal805]

Inquiring old minds want to know. . . . .these cars were not designed for overflow tank and none of my cars overheat, even my 05 Vette does'nt use the OT. So my question is what is the point?

In my case, it is to pass tech inspection at the track (NHRA)

 

[57vette]

Is there a rule of thumb or caution about how far from the radiator you can put an Expansion tank? I know some guys have mounted them on the opposite (drivers) side. My PS firewall is looking better and better bc it’s pretty empty, and I’ve already got my PS reservoir on the drivers side of the core support. I use a cover over the front “cavity” so I don’t want to bury the tank where I can’t get at it without removing all the tie down bolts.
The firewall isn’t much further than the DS of the radiator.

Mike

 

[dhutton]

Is there a rule of thumb or caution about how far from the radiator you can put an Expansion tank? I know some guys have mounted them on the opposite (drivers) side. My PS firewall is looking better and better bc it’s pretty empty, and I’ve already got my PS reservoir on the drivers side of the core support. I use a cover over the front “cavity” so I don’t want to bury the tank where I can’t get at it without removing all the tie down bolts.
The firewall isn’t much further than the DS of the radiator.

Mike

Makes no difference imho. A lot of overthinking going on here. This is not rocket science. Radiator pressure beyond cap pressure rating pushes coolant into tank. When radiator cools resulting vacuum pulls coolant back into radiator. Don’t obsess over level, system will find its operating level.

Don