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Where to tap in expansion tank

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blkcorvair

Jedi Knight
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I must admit I am not so cooling system savy. It would help I suppose if I could find a flow chart for the Midg 1500 water pump, Never the less here is my question. the 1975 Midg expoansion system was recalled (As I found out just as I was looking to use some parts off my donor car) So rather than try and scavange misc parts from here or there I decided to go all performance. Mainly this car will only see the track anyways. So I have a Moroso Exp. Tank in which the directions state to tap the oulet hose into the inlet fitting of the water pump. I have the tank higher than the water neck and was planning to find a later model water neck (which has a tee fitting already) to attach this too. My thought would be this would keep the system full and do a good job of collecting unwanted air (As the tank is now the highest point) So I am getting impaiteint (I wont have my hands on a later water neck til after Xmas. and was wondering if I could just tee this outlet hose into my heater core bypass tube, if that would indeed give the same affect? My other reason I was thinking I could tap into the water neck originally is because I could in theory use the expansion tank as a fill point as well. (Much more ideal than waiting for the tiny water neck to fill one teaspoon at a time.) If the water neck is the best choice does anyone on here have a 1976-1979 Midget 1500 neck they'd like to part with?
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Hi Scott, Generally the radiator neck contains a spigot that is fitted with a hose and routed off up under the car. Fitting an expansion tank can be accomplished by routing this hose to the expansion tank. Thermal expansion of the coolant pushes the water into the tank via the radiator cap's pressure valve. Whe the coolant cool and contracts it creates a vacuum which sucks the coolant bac in to the radiator. The tank can be located at any convenient point in the engine compartment. ---Fwiw--Keoke
 
Keoke said:
Hi Scott, Generally the radiator neck contains a spigot that is fitted with a hose and routed off up under the car.
Click to expand...

Correct

Keoke said:
Thermal expansion of the coolant pushes the water into the tank via the radiator cap's pressure valve.
Click to expand...

Correct

Keoke said:
When the coolant cools and contracts it creates a vacuum which sucks the coolant back in to the radiator.
Click to expand...

Not if you have left the radiator cap unmolested!
The spring/rubber seal in the cap lets air/water out to the overflow tube but doesn't let it back in, you need to change the cap so that it does not seal at the bottom of the radiator filler (take the rubber seal off) but does seal at the top where the lid of the cap touches the top of the radiator filler so that the rad can breathe in and out of the expansion tank.
 
I have wondered about using the expansion tank on the bugeye and the explaination above is good. Looking int rads is something of an art few really want to discuss. BE have a 1" neck, would a 3/4" neck one work.
 
racingenglishcars said:
I suggest against a heater bypass tube. Originally the heater could be blocked off by the heater valve, or when the valve was open, the heater provided a bit of cooling for the engine. With just a bypass tube, hot water is directed directly back to the engine without cooling.
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I forgot many of these were outfitted with Shut off Valves. So Ideally I can simply plug the Heater outlet/inlet all together w/o hurting anything. FYI. The 1975 Radiator has no cap or neck. This was built into the expansion tank and filling is done threw the thermostat water neck. It lacked an overflow tube althogether. (One rason I think this system was factory recalled.) The new expan. tank I have is setup up with a cap and overflow to achieve this.
 
I would suspect the reason for recalling those was for the reason they were a bear to refill. And if not done properly the car would overheat causing the owner unnecessay expense.

Header tanks work great, but you should do it like the VW golf. About a 1" diameter hose from the bottom of the header tank to a T fitting on the lower radiator hose, and a very small bleeder hose from high in the engine / radiator up to high on the header tank.
 
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