Surge (expansion) tanks, is it worth adding?

[Hart_Rod]

I'm debating on adding a surge (expansion) tank to the cooling system on my 68 supercharged truck. My current system works well, but I've been reading up on the LS cooling systems, and it seems tha all modern engines are designed to have a surge tank. I know most hot rodders and retrofitters don't add them due to lack of space or cost considerations, but I'm wondering if it would be beneficial to the engine and cooling system to make it work like it was designed.

Here's some heaving reading on the subject:

http://www.pirate4x4.com/tech/billav...CoolingSystems

I'm just curious if anyone has added the surge tank after the fact and if you have noticed a difference in how your engine cools? Thoughts and opinions are welcomed!

[Wasted Income]

Nah. Not needed.

Just do a good coolant recovery tank (not just an overflow), and you'll be golden.

[Hart_Rod]

Originally Posted by Wasted Income

Nah. Not needed.

Just do a good coolant recovery tank (not just an overflow), and you'll be golden.

Thanks WI. Not sure I know what the difference is between a recovery tank and an overflow?

[BR3W CITY]

I'm just running an overflow myself, never noticed an issue with it, tho I myself don't know what differs a surge vs recovery tank. AFAIK the overflow is a one-way street, when it boils over, it dumps to overflow. Surge tank and recovery sound like they might do the same thing....anyone want to elaborate?

[Wasted Income]

An overflow is just a "puke tank" once coolant is in there, it's there for good. This will cause an air pocket at the top of the radiator when the engine cools down, and the coolant contracts, and the radiator sucks in air. Overflow is vented to atmosphere.

A coolant recovery acts the same as an overflow tank, but it feeds/draws from the bottom of the tank, allowing the vacuum created in the radiator upon cool down to suck coolant back into the radiator. Basically it keep the radiator filled at all times, even as air is purged from the system. Recovery is also vented to atmosphere, and will allow trapped air in the radiator to be purged from the system.

A surge tank is pressurized, and is normally used when the radiator fill neck is NOT the highest point in the system. This allows air that would otherwise be trapped in the cooling system to purge to the surge tank, and also allows expansion of the coolant. The surge tank is always the highest point in the system. The "radiator cap" is located on the surge tank, not the radiator. They are especially useful on cars like corvettes where the radiator is "layed down" and not the highest point in the system any longer.

[homemade87]

The overflow tank does move fluid both ways and it does keep the radiator full. Have you ever noticed the side of a overflow tank . It has a full cold and a full hot. It also has a hose that goes to the bottom. When the engine heats up it will push fluid or air from the system to the overflow and when it cools it will pull the fluid back to the radiator . If you have looked at the radiator cap it has a seal at the bottom and one just under the cap. This what allows the fluid to move both ways. When the engine cools the vacuum will pull the fluid back in to keep the radiator full. If you have a bad seal on the radiator cap it will not work properly .It works just like the late model surge tank to keep the radiator full and there is no need to have both. Give it a try, you will see the radiator will be full when you open it when it is cold. Before the overflow tank days on vehicles when you opened the cold radiator the level would be about 3" from the top. This works great on both my ls2 swaps to keep the system full.

[Wasted Income]

Originally Posted by homemade87

The overflow tank does move fluid both ways and it does keep the radiator full. Have you ever noticed the side of a overflow tank . It has a full cold and a full hot. It also has a hose that goes to the bottom.

The part in bold above makes it a recovery tank, like I described. An overflow tank / puke tank / catch can simply catches the expelled coolant to keep it from leaking on the ground, or spraying under the hood. These have a port in the top of the tank/can that does not reach the bottom to allow the coolant to siphon back into the radiator.

We're talking about the same thing, with confusion over nomenclature.

[Wasted Income]

More good info here.

http://homepages.donobi.net/sufuelpu...YSTEMS_AND.pdf

[BR3W CITY]

Is this is an overflow or a recovery? I was thinkin overflow, but based on your description its a recovery? I have one pretty much like this, I still have a normal radiator with cap etc.

[oldman3]

Hey Hart Rod, just wanted to let you know that I finally got the bounce problem on Jimbo's long bed taken correct. Here's the link to the thread it's on the last page http://67-72chevytrucks.com/vboard/s...d.php?t=574720 ...Jim

[Andy4639]

From everything I have read on the surge tank it's only needed if the radiator isn't the highest point in the cooling system. With that being so then I can't see how it could help the motor in any way on these models since the cap is the highest point.

The recovery tank are over flow tank which ever you prefer to call it is a good idea to install on any engine.
I personally have never seen a over flow tank that didn't have the hose in the bottom of it! Weather it runs through the top and down to the bottom are goes in at the bottom.

[homemade87]

After doing some reading it seems that the ls motors has a tendency to aerate the coolant. Reason for the steam lines on the heads. When they moved the thermostat down low there was no place for the air/steam to go but up to the heads. So the heads would trap air. One way for them to combat this was to add a surge tank that had continuous water flow thru it to remove all air/steam from the system while running at all times. I guess they felt this was the best way to keep from having any chance of a hot spot in the upper part of the motor from air pocket.

I still feel if you have properly installed your steam lines and have a recovery tank you would be fine. I still don't see the need to install a surge tank. The recovery will keep your radiator full and still get rid of any air when it goes thru the thermal cycle provided you have a good working radiator cap.

[Wasted Income]

^ This.