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Topic: Expansion Tank

in Forum: C3 Cooling and Heating Systems


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Re: Expansion Tank (7/17)
 3/24/13 7:08pm
F4GaryGold Member
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Grapevine, TX - USA

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1972 LT-1 convertible with factory air.


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Wow, I never realized those years had that.  My LT-1 just has an overflow hose to the ground. 

So why was it designed that way with the heater hose going through it?  Doesn't make sense to me.


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Re: Expansion Tank (8/17)
 3/24/13 10:40pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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The design concept is similar to what you have in your water heater at home(or storage tank of a system with well water). There needs to be a space at the top that is nothing but air...a cushion of sorts. It also provides an amount of compression in the system. This is what keeps the tank from just filling all the way to the top with the engine running. As long as there is a specific, minimum amount of free air space in the tank, you should have NO leakage/spillage out of the tank under normal operating conditions. "Normal" meaning that the radiator does NOT also have a radiator cap on it, the cap on the expansion tank is holding the specified pressure, and the engine is not overheating. 

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Re: Expansion Tank (9/17)
 3/26/13 1:25pm
rraider1
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Woodland, WA - USA

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Re: Expansion Tank (10/17)
 3/26/13 7:32pm
rod7515Lifetime Member
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Bob, thats interesting as they are marked 68-72 and 69-72. I have a 72 and dont have a tank like htat on mind. Does it just represent BB cars or maybe ones with AC? Mines a small block with no air. Hope it helps the original poster.
Rodney


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Re: Expansion Tank (11/17)
 3/26/13 10:25pm
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Supposedly, in '68, none of the big blocks had the expansion tank, even tho the L-88s did. In '69, SOME of the big blocks had one. I think it had to do with the radiator used for the specific engine. I think the engines with the aluminuminum radiators used the expansion tank, but not the copper radiators. Don't know for sure, tho...the info I have is confusing, at best.Confused

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Re: Expansion Tank (12/17)
 3/27/13 7:37pm
rlu1968
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Gordonvillle, TX - USA

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Now I understand, somewhat! 
I had a radiator cap on the radiator as well as on the expansion tank. The expansion tank just filled up and overflowed. So instead of having a sealed cap for the radiator just put a regular cap on the radiator (has to be caped) and put the sealed cap on the expansion tank and fill it close to half way and it should not overflow.
RICHT??? 
I just took the whole darn thing off, I really don't need it anyway. 


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Re: Expansion Tank (13/17)
 3/28/13 9:58am
rraider1
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Woodland, WA - USA

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Here is some more info I found hopefully someone can add it all up and fill in some gaps

the long expansion tank is for 69 to 72 427/454 W/AC copper Rad
 
The barrel expansion tank is for 68 to 72 with Aluminum Rad all 327/350 Except 70 to 72 LT1 and 68-69 WO AC
 
Plastic coolant Recovery started 73
 
The expansion tanks are presurized systems and depends on type of radiator I beleive do not have a cap on them the cap is on the tank?
The plastic ones are coolant recovery non presurized started 73

 

 RADIATOR: There are two types in Corvettes – the stacked-plate aluminum Harrison design with a separate expansion tank, and the conventional copper/brass type with no expansion tank. The Harrison aluminum design is by far the more efficient, as it has the most fin-to-tube contact area, which is how the heat is transferred to the air. Copper/brass conventional radiators need larger cores, as they have less fin-to-tube contact area due to having narrower tubes, and they’re heavier. Another key difference is that aluminum radiators can’t be repaired, and they’re expensive to replace; copper/brass radiators can

be repaired or re-cored using the original side tanks, and they’re also less expensive to replace.

EXPANSION TANK: Conventional copper/brass radiators with fill openings have side tanks that serve as reservoirs to accommodate coolant expansion; that’s why the “Full Cold” mark is several inches below the filler neck – to allow for expansion of hot coolant. The Harrison stacked plate aluminum radiator has no side tanks – it’s all core, from end to end, so it needs an external reservoir to provide a fill point and to accommodate coolant expansion. The companion Harrison aluminum tank has the cap/fill point, an inlet from the top of the radiator to provide a path to the tank for expanded coolant, an overflow hose

from the filler neck, and the bottom of the tank has a fitting connected with a tee to the return hose from the heater core to the water pump inlet fitting so the tank is connected to the coolant circulation system and functions as a reservoir. They are trouble-free unless the relatively thin aluminum has been attacked by corrosion (which is why they use a unique RC-26 filler cap with no plain steel exposed to the coolant).



|UPDATED|3/28/2013 6:58:40 AM (AZT)|/UPDATED|
Re: Expansion Tank (14/17)
 3/27/13 8:09pm
dyoes
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Zachary, LA - USA

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Hopefully I'm not being redundant, and more importantly I hope I'm accurate. The early Sharks had a pressurized expansion tank. The radiator and expansion tank caps were not vented as the later ones were, although I believe the expansion tank had a relief function. As water heats, it expands, and level rises in the expansion tank. Taking the cap off of the expansion tank is just like uncapping a hot radiator: it's under pressure, and will flash to steam if over 212F. The expansion line can be hooked up anywhere in the system, it really doesn't matter, as it's just additional volume for the system and keeps the radiator solid. The later ones (74 and up, I believe?) had a siphon/relief type coolant reservoir. Not technically an expansion tank. The radiator has a different type of cap: it both relieves on high pressure, and opens for reverse flow as the radiator cools (and the coolant subsequently contracts, forming a vacuum in the radiator). So excess water is displaced through the cap into the reservoir when it's hot, and sucked back into the radiator when it's cold. The reservoir is not under any pressure and is constantly vented to the atmosphere. Explains the "hot" and "cold" fluid levels on the reservoir. Two different ways of tackling the same problem: water expands when it gets hot. But in the later application, car makers don't have to worry about people burning themselves while checking coolant level. Earlier cars didn't have either one: you simply didn't fill the radiator up all the way. Fill it up too full, and it would relieve out onto the ground (someone mentioned an overflow line straight to the ground: that's it!). Hopefully I've gotten this right. Let me know if I've but out bad info, my skin isn't thin. :) Darryl

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Re: Expansion Tank (15/17)
 3/27/13 8:31pm
dyoes
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Zachary, LA - USA

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1974 L-48 Auto. Just your basic Vette. GM crate motor w/vortec heads and intake. Crane cam. Scorpion rockers, Edelbrock carb. Lots of parts still in boxes... :(


Joined: 1/27/2013
Posts: 201

Oh: one way to avoid the expansion tank is to install a catch can (vented). Change the radiator cap to a late model one, and buy a cheap expansion tank and run a hose to it. The hose has to go all the way to the bottom so it can siphon back in... I've seen hot rodders use a longneck beer bottle and a hose. It doesn't have to be high tech!

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Re: Expansion Tank (16/17)
 3/28/13 10:00am
rraider1
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Woodland, WA - USA

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I tried to update the applications if someone sees something wrong please correct
 
 
the long expansion tank is for 69 to 72 427/454 W/AC copper Rad
 
The barrel expansion tank is for 68 to 72 with Aluminum Rad all 327/350 Except 70 to 72 LT1 and 68-69 WO AC
 
Plastic coolant Recovery started 73
Re: Expansion Tank (17/17)
 3/28/13 12:15pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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rlu1968 said: I had a radiator cap on the radiator as well as on the expansion tank.


My unnerstanding is that combo will NOT work...as you have discovered. You cannot have two pressure caps in the system.
Bob...I've never seen the longer skinny surge tank...neat! Thanks for sharing that info, too!


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