How to add Expansion tank to a car without one?

It helps to know what year and type of car you are converting.

Most cars have an overflow/surge tank that helps to keep air out of the system and prevents coolant loss. This is not to be confused with a header tank of which you speak.

The tank on the 308 is there to act as the highest point of the cooling system where coolant can be added and air can be purged. It has a constant flow of coolant through a feed and return line attached at two points on the thermostat housing. A unique set up you won't find on most cars.

To add a similar tank with circulation you would have to tap into your heater core supply line BEFORE the temp control valve and again on the heater return line or the main radiator return line.

The big question is, 'Why are you increasing the capacity?"
Dumping more coolant into a tank doesn't offer much advantage over the original system.

If you have a cooling problem the best fix is to increase the cooling ABILITY of the system, usually a bigger(another row of tubes in the core) and better (crossflow) radiator is how to do this. This will increase the exchange area and increase the capacity.

 

I did this to my 308 years ago, works great and catches all the overflow that would have normally spilled on the ground/track.
john
78 308 GTS euro
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Again, from my first post;

To add a similar tank (header type) with circulation you would have to tap into your heater core supply line BEFORE the temp control valve and again on the heater return line or the main radiator return line.

In addition, if possible you may be able to tap into the water pump bypass if it has one.

 

Could you answer a question for me then,

How does adding a circulating header tank and extra coolant make a difference?. It seems to me that circulating coolant through a tank is just that, circulating coolant through a tank. It may cool somewhat but ?

Take no offense, just trying to figure out what you are trying to accomplish. Exchange of ideas etc............

 

Spasso,

i have a feeling he wants to do as i am going to do shortly. Basically, when things get REALLY hot on the track, the rear coolant tank can spew out a bit of fluids. On a track you can be flagged for this and away you go

This extra tank will catch the "extra" fluids and also hold them. i have heard that, at times, some fluid MAY go back from the extra tank to the stock one, yet have ZERO personal experience about this. As the pics above show, just add another tank to catch/hold said fluids. This is on my list of mods to the 308 here.

 

Steve,
What you are describing is called a SURGE tank not a HEADER tank and I have one installed on my 308 presently. It prevents coolant from pissing on the ground when the engine reaches max temps and draws the coolant back into the HEADER tank when things cool off a bit , changing an open system to a closed system.

Billet Specialties has a real nice aluminum one about 18" long by 2" in diameter. I'll post a picture of it when I get home if anyone is interested.

 

Actually, this is specifically what he is NOT trying to do...he said he is trying to add coolant capacity to his system, by way of an expansion tank. He also believes this might add cooling capability to the system, which DJ believes is not correct...or at least not the best method to do so. We are waiting for further details from 308GTS....

Dave

 

Well, in that case, the easiest way is to leave it in the box and throw it in the truck where it will do the least harm. Without more info, that is the only place it belongs.

Adding volume to a cooling system increases it's heat storage capacity, not the cooling capacity....so it will still overheat, just not quite as soon. It helps at the drag strip. Is That what you are trying to do?

Anyway, The easyest way to have coolant flow through a tank, for whatever reason, is to mount it as a bypass in the heating system. So "T" the heater lines, the feed to the top on the tank, the return out the bottom of the tank, be sure you do it before they get to the heater control valve. Yuo will have a flow throw tank, but your heater won't work as well if at all. The other option is to make a "T" you can slice into the hoses going and coming from the radiator

 

You are indeed correct. i guess if he wanted better cooling capabilities he would be better off with a new/better radiator. Have been debating doing this for the 308 here, yet temps are always very good so there has been little incentive to do so.

 

The chrome cylinder to the right of the header tank is my surge tank. The top unscrews for cleaning and inspection. It fills through the bottom from the neck of the header tank when the pressure cap opens. It has a stand pipe inside that acts as an overflow if the system is over filled. It has a 16 oz capacity that works okay for the street but I would recommend the 20 oz for extreme usage.
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