1950s 57 Radiator Issue

[FabCad]

My 57 Eldorado started spewing coolant from the overflow line on the radiator. This happens when the car is warm and driving (not just idling). The car is not overheating and the coolant level is not overly full. What would cause this?

Thanks,
Fab

[Big Fins]

Have you recently changed or added coolant? Is there an overflow bottle being used? The level of the coolant in the radiator should be approximately 1 1/2" below the flange in which the seal of the radiator cap rests.

It's also bee excessively hot lately and the coolant level may be looking for it's own level. An overflow bottle may not be factory, but it sure does help in the maintaining the proper level in the system.

[FabCad]

I have not added any coolant lately, other than to replace what has leaked out. Yes, the coolant was filled 1-1/2" below the flange, give or take. It is leaking out to the point where there's no longer any coolant visible inside the top of the radiator.

No overflow reservoir.

I drove it yesterday in the morning when it was still cool out, so I don't think it was the heat.

Could it be a bad thermostat?
 

[Big Fins]

Loss of coolant means a leak, a split seam, bad cap or heaven forbid, freeze plugs.

Better look into that a little deeper.

[Clewisiii]

I put a large sheet of brown paper under my car while running to help me find the drips. I had a lower hose that had an intermittent leak at the clamp.

[Cadillac Jack 82]

Could be the water pump too.  I was having issues with overflow in the 59 before the pump failed. 

[Jon S]

OP says it is coming out the overflow. I suspect the radiator needs a good cleaning.

[FabCad]

So today I replaced the radiator cap  and drove it. No leakage. Not sure if that truly resolved the issue or what. But I'd be a bit surprised if it was that easy of a fix.

[Big Fins]

Why? The rubber seals go bad and the springs get weak over time. Kinda like us if you think about it. 

Monitor it. It's nice to thrown a bone now and then.

[FabCad]

Makes sense!

Do you happen to know what is the correct cap for a 57 Cadillac? (vented vs non-vented, psi)

[Cadillac Jack 82]

RC-6 and 13#

[Cadillac Jack 82]

https://www.caddydaddy.com/1949-1950-1951-1952-1953-1954-1955-1956-1957-1958-1959-1960-cadillac-see-details-radiator-filler-cap-nos-free-shipping-in-the-usa.html

[FabCad]

Thank you!!

[Big Fins]

No sir. Looks like you got a satisfactory answer.

[dn010]

If you are not going for originality and don't want to pay nearly $100 for a cap, I have been using the cap below since 2020 on my 57 when I suffered the same issue as you did with a leaky cap. No issues whatsoever.

https://www.amazon.com/Gates-31511-Safety-Vent-Cap/dp/B000C2WEV4

[Cadillac Jack 82]

Dan those latch type caps are a recipe for issues.  Stant makes a similar 13# one that works as well.

[FabCad]

I ended up buying one of these on Amazon. Hopefully it does the trick.

https://www.amazon.com/ACDelco-RC6-Professional-P-S-I-Radiator/dp/B000C9TZOQ/

[TJ Hopland]

That link looks spooky.....  not that the name really matters since those are easy to spoof.

If you have a tractor supply farm and fleet sort of place near you old tractors used lower pressure caps like that and those places often stock them.  I'm sure just about every parts store stocks them too but they can't look it up so its up to you to figure out their part number and then walk in and ask for it by part number.

One of my cars had a AC cap on it.  Stood for Allis Chalmers but I'm sure most people if they even noticed assumed that was AC Delco....  what does the AC in Delco stand for anyway?

[FabCad]

Link updated above

[Big Fins]

what does the AC in Delco stand for anyway?

Of course AC spark plugs were used in GM's concept cars: AC (ACDelco) was a division of GM. But did you know that AC were the initials of Albert Champion, who gave his name to that eponymous spark plug company.