Learning how to build Lotus Seven replicas...together!
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PostPosted: November 20, 2021, 12:29 pm 

Joined: August 18, 2015, 12:41 pm
Posts: 117
Location: Seattle area (Woodinville)
The Raceline water rail does not have provision for use with an expansion tank. I'm guessing that it is intended to be used simply with a catch tank. The heated water flows out the escape tube into the catch tank and is drawn back as it cools. Which is the way they work when there is an expansion tank. But after a lot of research, on the web and in books, I have been unable to find any reference to a cooling system that doesn't have and expansion tank.

Am I missing something her? (besides an expansion tank?)

Jerry Henneman

Jack of many trades
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PostPosted: November 20, 2021, 4:27 pm 

Joined: February 8, 2014, 10:47 pm
Posts: 753
Location: Cornholio OR "Where the magic happens"
You can't seal the cooling system without an expansion tank.
You don't want any air introduced into the system to prevent corrosion and loss of cooling ability.
So yes you are missing an expansion tank, there are two ways to do it.
One way the tank is pressurized, the other is unpressurized, there has to be a way for the coolant to expand.
Older less educated designs just used the upper tank of the radiator for an expansion tank.
Engineers have learned that is not the best method, it also requires that the rad top tank is the highest point in the system.
Todays cars and Locost's both have radiators that are often below the top of the motor.
This low mounted radiator mandates an expansion tank, or a recovery tank in the system.
The advantage of a pressurized expansion tank is a vent line can be run from the top of the radiator to allow any trapped air bubbles to vent to the expansion tank.

I don't know who I am, when I am somebody else.

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PostPosted: November 20, 2021, 7:09 pm 
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Joined: December 22, 2006, 2:05 pm
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Location: "Banana Republic"
Jerry, pics go a long way.
The typical raceline rail is part of the pressurized cooling system with the upper hose neck attached to the top of it. Sometimes there is a fill cap on the neck.

1) You need an overflow/catch can connected to a small nipple near the radiator cap. The cap releases coolant at this point when the pressure exceeds the cap rating, usually every time the engine is shut off.
2) You need a fill point at the high point. It used to be the radiator in older machines.

An expansion tank is not required but is more effective at eliminating air pockets if mounted to be the highest point in the system. '60s Shelby cobras had expansion tanks. I've used this one for VWs but you need to make a bracket to hold it up, not just the bolt flange. It tees into a heater hose fitting:

https://www.ebay.com/itm/333816653050?_ ... BMmoX7-Kdf

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