[Tech] Explain the difference to me.
Thread Starter
Le Mans Master
Joined: Sep 2000
Posts: 9,078
Likes: 7
From: DFW TX
Cruise-In VII Veteran
St. Jude Donor '07
[Tech] Explain the difference to me.
Between using an closed and open clooing system with an overflow. Currently I just have a tube hanging down with no overflow tank, the cap is a pop off type. 
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Ok, here's my attempt....
Water expands when hot so you need more space for it when the engine is up to temp. Old cars just didn't fill the radiator all the way and left a big airpocket for the water to expand into. Drawback was that this big sirpocket could move into the engine forming an airpocket that led to overheating. Note that the gauge would not tell you since it would be in water that was ok, yet where the airpocket was the temps would skyrocket.
Another problem was that corrosion needs air, and air was in there = corrosion.
Later systems used an expansion tank. It was a pressurized tank with enough air in for the coolant to expand into. Still had the corrosion issue. Airpockets were mostly fixed due to the design of the expansion tank would keep air out of the engine.
Finally, modern systems push the extra coolant past a pressure valve (the cap) into an unpressurized overflow tank and then suck it back in when cooling off. This is by far the best system as there is no air in the pressurized system plus it is real easy to check the coolant level.
Water expands when hot so you need more space for it when the engine is up to temp. Old cars just didn't fill the radiator all the way and left a big airpocket for the water to expand into. Drawback was that this big sirpocket could move into the engine forming an airpocket that led to overheating. Note that the gauge would not tell you since it would be in water that was ok, yet where the airpocket was the temps would skyrocket.
Another problem was that corrosion needs air, and air was in there = corrosion.
Later systems used an expansion tank. It was a pressurized tank with enough air in for the coolant to expand into. Still had the corrosion issue. Airpockets were mostly fixed due to the design of the expansion tank would keep air out of the engine.
Finally, modern systems push the extra coolant past a pressure valve (the cap) into an unpressurized overflow tank and then suck it back in when cooling off. This is by far the best system as there is no air in the pressurized system plus it is real easy to check the coolant level.
Thread Starter
Le Mans Master
Joined: Sep 2000
Posts: 9,078
Likes: 7
From: DFW TX
Cruise-In VII Veteran
St. Jude Donor '07
Thanks, Markus
I guess for a daily driver, I will go with the unpressurized overflow tank. Since the conversion, I need the space for the PCM and now need to convert back to something. Somewhere down the road someone changed the cap and converted it to a pop off type. Probably because the tank cracked. I changed out the tank, but never got around to changing the cap. Off to the Jegs catalog for a tank.
I guess for a daily driver, I will go with the unpressurized overflow tank. Since the conversion, I need the space for the PCM and now need to convert back to something. Somewhere down the road someone changed the cap and converted it to a pop off type. Probably because the tank cracked. I changed out the tank, but never got around to changing the cap. Off to the Jegs catalog for a tank.
