Is there a reason other than room not to plumb the cooling system in a more conventional way where the outlet from the engine thermostat goes to the expansion tank then from the tank to the radiator rather than teeing off a smaller line to the expansion tank? Do you get better flow or less of a possibility of air being introduced going directly to the radiator?
Cooling System Plumbing
- Thread starter Paul Thon
- Start date
Howard Jones
Supporter
The inlet from the expansion tank, AN8 or 10, MUST come from the lowest practicable pressure and coolant temp location. This is normally right at the water pump input/face of the pump impeller. At that point, the coolant has traveled from the hottest point in the system, the top of the intake manifold/thermostat to the radiator, been cooled, and returned back to the rear of the car to be pumped through the engine again to absorb heat.
The bleed system MUST deliver the air from the highest points in the system where the air will collect, the top of the radiator tanks, the top of the intake manifold, and the rear of the heads at the intake manifold where the heads water ports are exposed, back to the expansion tank. BUT the size of the lines in the bleed system must not cause a bypass effect so they should not be larger than AN-4. Big enough to bleed air out but not big enough to interfere with the correct coolant flow throughout the engine.
I have placed a bleed line from the very top of the thermostat housing to the expansion tank, the rear of the heads, and both sides of the radiator tops. This system works so well that if I drain the system to take the engine out of the car for example I simply fill the system back up from the radiator cap and let the bleed system bleed all the air out without any other additional procedures/ Works perfectly every time.
You can try anything you want to but the above is the most effective way. LS engines and 4-valve fords have sightly different internal plumbing but the basics of how this all works remain the same.
The purpose of the expansion tank is to allow for the coolant to increase in pressure and have a place to act as an accumulator for any air to be separated from the coolant in the system. This is why it needs to be higher than the coolant volume and located as high up in the chassis as possible. Flowing coolant through the expansion tank as you suggest will mix the air in the top of the expansion tank with the coolant volume, Exactly what you do not want to do.
The bleed system MUST deliver the air from the highest points in the system where the air will collect, the top of the radiator tanks, the top of the intake manifold, and the rear of the heads at the intake manifold where the heads water ports are exposed, back to the expansion tank. BUT the size of the lines in the bleed system must not cause a bypass effect so they should not be larger than AN-4. Big enough to bleed air out but not big enough to interfere with the correct coolant flow throughout the engine.
I have placed a bleed line from the very top of the thermostat housing to the expansion tank, the rear of the heads, and both sides of the radiator tops. This system works so well that if I drain the system to take the engine out of the car for example I simply fill the system back up from the radiator cap and let the bleed system bleed all the air out without any other additional procedures/ Works perfectly every time.
You can try anything you want to but the above is the most effective way. LS engines and 4-valve fords have sightly different internal plumbing but the basics of how this all works remain the same.
The purpose of the expansion tank is to allow for the coolant to increase in pressure and have a place to act as an accumulator for any air to be separated from the coolant in the system. This is why it needs to be higher than the coolant volume and located as high up in the chassis as possible. Flowing coolant through the expansion tank as you suggest will mix the air in the top of the expansion tank with the coolant volume, Exactly what you do not want to do.
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Thanks, makes sense. Wondered as the Cobras ran the coolant thru the expansion tank, less plumbing but I see now where separate bleeds would help get the air out since the radiator is so low and far away. Time to plumb away...
Howard,
This is the most clear and concise description of how a cooling system should work, backed up by experience. Thanks for taking the time to post!
Kind regards,
Julian
Looks like the magnetic plug/drain from a Honeywell 36-150 APU
Neil
Supporter
Thanks, I wondered where it may have come from. It is a real jewel.
Davidmgbv8
Supporter
JEGS 51108: Air Bleed Valve 1/8" NPT - JEGS
air bleed valve, air relief valve, coolant air bleeder, coolant bleed valve, radiator bleed valve
www.jegs.com
Neil
Supporter
Those would work nicely. I paid about $1 for mine.JEGS 51108: Air Bleed Valve 1/8" NPT - JEGS
air bleed valve, air relief valve, coolant air bleeder, coolant bleed valve, radiator bleed valve
Howard Jones
Supporter
The system I describe above does not require a manual bleed/burp valve. If all the air accumulation points are permanently vented via the bleed lines to the expansion tank and if the tank is located at the highest point possible in the car as it should be, then any air in the system MUST all end up in the open volume at the top of the expansion tank. Right where it should be, under the radiator cap or blown out to a separate catch tank with any overfill volume of coolant. Catch tanks normally are vented to the atmosphere. I mount mine low and behind the rear wheels with an overflow line directed down at the road should it fill. I drain my overflow tank as necessary and keep it empty.
Davidmgbv8
Supporter
True, I will just put a 2’ flex hose with a plug to vent my radiator. I will do something similar for my clutch bleed. Making a remote bleeder where you can lift up the hose and quickly and easily bleed vs trying to get your hands under the exhaust.
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