Coolant expansion tank question

Dimi Terleckyj

Lifetime Supporter
Hi Ben

The answer is all dependent on how much coolant is in your particular system and how much it will expand and still leave some airspace in the coolant recovery tank at full heat.

If the coolant expands and the tank is too small some will be lost during each cycle and your system will suck in air as it cools down.

In my 40 with a 5.4 Mod motor I needed a 3 litre recovery tank to avoid losing any coolant.

I'm using the 1 1/4 quart. The 1 1/2qt. was perfect for my 408 ...... I think the biggest factor is where you place it - gotta be above the highest point in the system. I havn't lost a drop of coolant from it yet.
Thanks Dimi. I will be using a LS376/480 engine.

Alex: I was planning on copying the placement like in the photo below. I think this is where everyone else is putting it.


Roger that Doc. Yesterday I was thinking about what materials I would use to create the gap.

Jack, any particular threads off the top of your head?
Fran is using them now. Dorman PN# 2060200 at your favorite Autozone, etc.

Here are the hook-ups on the chassis, perhaps Wayne can post a pic or two:
Dorman coolant tank

to mount tank, go as high as you can with the spyder in place so you can access the tank cap and close the rear clip. Two brackets needed.
trim off any protrusions on the tank that get in the way.


the bottom of the main drivers side coolant tube requires a straight one-inch spud (long enough to get a hose on) that goes to the one-inch connection on the bottom of the Dorman tank. they use a straight piece of one-inch ID hose.

there are two 3/8" connections on the tank. the front one goes to the drivers side radiator bleed fitting on drivers side. use a 90 degree fitting on the radiator.

the rear 3/8" fitting on the Dorman tank goes to the steam vent line on the engine.

Michael Holmes

Lifetime Supporter
Michael: I was talking to Allan today, who also highly suggested the Canton tanks. Thanks a bunch for the link.

Michael Holmes

Lifetime Supporter
make sure that the expansion tank is the highest point of the cooling system, where any air will collect. I installed a hose fitting in my intake manifold which allows me to attach water to force any air out the expansion tank. The overflow can be placed anywhere, this is where I put my coolant which will eventually mix with the water. THIS MAY NOT BE ADVISABLE FOR COLD WEATHER CARS.

Also once the system is free of air i never remove the cap from the expansion tank, only the overflow tank. Or you will get air in the system and will have to purge again.
Thanks for the tips Michael!

Excellent link Howard. As usual, I appreciate your help.

In all honesty, I'm feeling like I may have bitten off more than I can chew with this entire project. Threads and postings are helpful, but most of the terminology used is completely foreign to me, so I have to Google it. It's tough to admit ignorance. Maybe things will become clearer when I actually have the car in my garage.
Ben I am at the same spot on my car with the cooling system it is hard to under stand when people call the same part five different names.try to look at Chuck and Ryan build they had the same problem and brake it down and make it simple.

Doc Kaler

GT40s Supporter
"Roger that Doc. Yesterday I was thinking about what materials I would use to create the gap."

I am using a 2" thick square of polyethylene as an insulator. This is untested so I am hoping it is the right solution. I also have gold foil on the bulkhead to mitigate heat transfer.

Don't despair about the scope of the project Ben. I am far from skilled at this (I'd rather be driving on the track). But, with the car in front of me, I see enormous potential and that keeps me going. We have a great SLC community as a resource.

New challenges come up all the time. Overcoming them, finding the solutions, is part of the journey that's very rewarding.