Expansion tank capacity?

Julian West · 11-20-06, 09:53 AM

What size should the expansion tank be for a 302 engined car?

I presume the level in the tank will change depending on coolant temperature.

Also I understand the tank needs to be mounted so the water level is always higher than the thermostat housing, is this correct?

With regard to inlets & outlets, I guess the main outlet will be to the top hose, & a second smaller hose to the radiator bleed. Are there any other connections I should need?

Finally, anyone got any pictures of ally expansion tanks?

Thanks in advance!!

Mark Clapp · 11-20-06, 10:15 AM

Julian, I went with the 1.5 quart Moroso tank as can be seen on this web page from Jegs: Moroso Cooling System Expansion Tank - JEGS
I plumbed the bottom outlet to one of the water pump "heater line" inputs. There is also a threaded fitting that I plumbed the bleeder line into. As for the level in the tank, I keep it completely full as it throws off/sucks back through the radiator cap side outlet, which goes to an overflow bottle.

Lynn · 11-20-06, 10:36 AM

Julian,

Don't confuse a swirlpot with the expansion tank; you'll want BOTH. You should put a ≈1 Qt. swirlpot in so that it is the highest point in the system. You'll put your pressure cap on this tank and a tube from the nipple on the low pressure side of the seal to the expansion tank. This tank should allow excess fluid to be captured AND returned to the system as it cools. It should also let gasses escape to the atmosphere. I have a little tube that runs from the top of the expansion tank down through the bottom of the sill panel. I've never had my $11 J.C.Whitney 2½ Qt. Overflow Bottle overflow on me. It looks very OEM as well.

Regards,
Lynn

Julian West · 11-20-06, 11:44 AM

Mark, Lynn,

Thanks for he replies, perhaps I used the wrong terminology, what I'm making could also be called the *header* tank, ie the high pressure tank with the radiator cap/fill point (much like the one in Mark's post Moroso Cooling System Expansion Tank - JEGS)

Is the low pressure tank a necessity? as both you guys are using one? If so, can the low pressure tank be mounted lower than the high pressure tank?

If the high pressure tank holds 1 & 1/2 quarts, what capacity should the low pressure tank be?

Any photo's of your setups would probably answer alot of my questions!

thanks for your time!

Mark Clapp · 11-20-06, 12:06 PM

Julian, yes it is the header tank. You should also use an overflow bottle or it is sometimes called a puke tank. My overflow is just 1 quart. It is just to accept the excess coolant after expansion. Once the system is cool, the void vacuum created sucks the coolant back to refill the system. This puking purges any air that collects in the top of the header tank. Most race tracks require an overflow bottle so coolant is not expelled onto the track. I will try to take some pics for you. The overflow can be plumbed lower than or anywhere around the header tank.

Julian West · 11-20-06, 01:09 PM

Hey Mark,

'puke tank' - now we're talking in language I understand! great!

thanks to your help, my spec is coming together now.....

Lynn · 11-20-06, 02:56 PM

Julian,

Here is a picture, although the expansion tank is somewhat hidden behind the roll bar brace. The "puke tank" is rather obvious. Some tracks insist on these puke tanks, btw. Anothere thing that is not real clear in this is the bleeder valve just above and to the left of the header tank (swirl pot.) There is a line that comes off of the intake manifold, rises even higher than the tank, connects to a brass bleeder valve and then connects to the line coming from the top of the radiator before dumping back into the header tank. I believe that this releases a lot of air that would otherwise be trapped during the fill.

Lynn

Julian West · 11-20-06, 04:53 PM

Thanks Lynn, I understand how your system works & appreciate your help.

SteveB · 11-20-06, 05:34 PM

Julian

Here is a pic of the header tank I am using. The small pipe connecton from the rad cap neck alows expanding coolant to pass to a container ( puke tank ) the radiator cap has a dual seal one regulates the maximum pressure in the system, exess is allowed to pass.
The lightweight sprung popet in the cap sealing flange allows the coolant to return as the system cools. This works only because there is a secondary seal between the cap and the top of the neck fitting, if this seal leaks, air is drawn back instead of syphoning the coolant back from the overflow bottle/tank.

The expansion tank is from MDA in Exeter

Hope this helps

Steve

Julian West · 01-06-07, 11:57 AM

Thanks all for your posts, Following your input, I had a small tank made locally.

We enlarged the size of the GTD filler pipe from 1/4" TO 5/8" and also put a connection in the tank for the bleed tube from the top of the radiator.

There is also a connection for a puke tank, but I haven't decided where to put it yet.

Now I can't wait to get the other jobs finished so I can fire it up & see how it all works!!

Eric A. · 01-06-07, 12:50 PM

Just to make sure that I have this all correct, and for the benefit of other members, is this how the tank is plumbed? The tank goes on the upper radiator hose with a connection, say 1 1/2 inch, on the bottom that is connected to the thermostat housing. Then there is another connection, same size, near the top, that goes to the line that runs to the front of the car to the upper inlet on the radiator. Then there is a connection for a small line that again runs to the front of the car and is the bleed from the top of the radiator. There is also a small line (size?) that has a line that goes from the tank to an inlet on the water pump. There is also the overflow line from the neck to a puke tank. Do I have this correct? If someone could post a schematic of the whole system it might help.

Mark Clapp · 01-06-07, 04:25 PM

Eric my header tank (Moroso 1.5-quart, see Moroso Cooling System Expansion Tank - JEGS has only three ports. One is on the tank bottom, which I have plumbed with heater hose (5/8") to one of the heater ports on the water pump (the other heater port on the water pump is capped off). This is where the system is filled from. Another port is high on the side of the tank and accepts the 1/4" bleed lines from the top of the radiator and the highest point on the intake manifold. These two bleed lines are tee'ed together then plumbed to the tank. The last port is on the side of the radiator cap housing and is plumbed with 1/4" line to a 1-quart overflow bottle (puke tank) to accept coolant after expansion. There are no connections to the 1.5" radiator line coming from the thermostat housing, it just runs up to the radiator inlet port, through the radiator, and back to the water pump as usual. This is my system and others may vary.

Larry · 01-06-07, 06:09 PM

Here is a photo of my header tank & overflow tanks.

Rob · 01-06-07, 07:22 PM

Very nice Larry.

May I ask where you got the tanks?

Rob

Larry · 01-06-07, 07:39 PM

Rob,
The Header tank came from the factory (Bailey Edwards Cars) and I had the overflow tank custom made to match.

Rob · 01-06-07, 10:39 PM

I figured..... Looks to good to have been purchased.

Nicely packaged..well done.

Ron Earp · 01-06-07, 10:44 PM

Hey Larry,

Where is the pressue hose on the side of the expansion tank going to?

Ron

Larry · 01-06-07, 11:47 PM

Ron,
The header tank (upper/left tank) is pressurized and when the coolant expands it overflows to the bottom of the expansion tank (lower/right).

Ron Earp · 01-07-07, 12:46 AM

Quote:

Originally Posted by car guy

Ron,
The header tank (upper/left tank) is pressurized and when the coolant expands it overflows to the bottom of the expansion tank (lower/right).

I understand that, but, you have a fitting off the bottom of the header tank that is pressurized and I was wondering where you teed it into - outflow from block, inflow from block, water neck bypass, etc.

Ron