This overflow line ?

[73Polara360]

Just curious if anyone has any more info on this line. I'm just curious about it. We determined it's some kind of expansion or overflow venting line. I haven't had time to consult my chassis manual sorry. I saw a small pool under the car after some normal driving in good conditions and traced it to this line. No broken nipples or anything it literally just terminates here. Overall car runs well, it appears to be exactly what the title says, but I'm just curious why it vents to atmosphere and not some evaporator can or secondary tank or something where it's not just pissing onto the ground. Good old 70s technology?

And under what conditions does it vent, because again, yesterday wasn't terribly hot and it wasn't spirited driving or anything rough.

Thank you

 

[RemCharger]

The factory literature dictates how to operate the vehicle, which was once common knowledge. Coolant expands when it's hot. Therefore if there is no where else to go, it will purge the excess. The good news is those old fellars easily figured it out, the upper tank is in fact the expansion tank. The level should be about an inch down from the top too to allow for said expansion. Once the system quits pissing out, it will be at the optimal level with no further action required.

 

[Big_John]

It's just the radiator overflow. When the coolant gets hot, it expands, and if there's not enough room in the radiator, pressure builds up, the radiator cap releases some pressure and it vents out to the ground.

If you open the radiator cap when cold (don't open hot unless you like to get burnt) the level shouldn't be right at the top. It should be down an inch or so from the top.

So, this really doesn't hurt anything, but the antifreeze is toxic and sweet to the taste, and pets may lick it up.

 

[CBODY67]

On many 1972 and later C-bodies, they did get a Coolant Overflow Tank near the a/c line to the receiver/drier. Which is where the coolant level was checked rather than at the radiator cap. The coolant recovery caps had a different seal to the radiator filler neck and as the hotter coolant would go to the jug, as the engine cooled, it would draw the coolant back into the radiator (hence the better seal than just "spring-copper.steel"). With the reservoirs, the old "1 inch below the bottom of the filler neck" level recommendation was superseded by "Check the coolant level in the coolant recovery reservoir". A visual check.

You car never had one of the reservoirs OEM. The displayed rubber overflow hose is typical of all cars which did not get a reservoir tank from the factory. In times all the way back to the earlier years before pressurized cooling systems.

Other than the aftermarket radiator cap, your car is "as designed".

As time progressed, the fibre gasket under the normal radiator cap seal seemed to be deleted. Possibly not needed. Existing caps would allow for coolant flow out and in.

CBODY67

 

[Lefty71]

Other than the aftermarket radiator cap, your car is "as designed".

Along those lines, wasnt it typical to see a slightly higher pressure rating on caps prior to the overflow bottle era??

 

[CBODY67]

They were all 15psi or 16psi, one way or another, as I recall.

 

[1970FuryConv]

Just curious if anyone has any more info on this line. I'm just curious about it. We determined it's some kind of expansion or overflow venting line. I haven't had time to consult my chassis manual sorry. I saw a small pool under the car after some normal driving in good conditions and traced it to this line. No broken nipples or anything it literally just terminates here. Overall car runs well, it appears to be exactly what the title says, but I'm just curious why it vents to atmosphere and not some evaporator can or secondary tank or something where it's not just pissing onto the ground. Good old 70s technology?

And under what conditions does it vent, because again, yesterday wasn't terribly hot and it wasn't spirited driving or anything rough.

Thank you

View attachment 733641

View attachment 733642

A cooling system overflow reservoir is an easy fix. Something like this can be purchased at an auto parts store.
1973 Monaco