One more radiator question

[Jonah D'Avella]

If my radiator is clogged up, is that what causes an overflow? Does the lack of flow through the radiator make it to a builds up in the top tank and over flows through the overflow tube?

[Ruxstel24]

If my radiator is clogged up, is that what causes an overflow? Does the lack of flow through the radiator make it to a builds up in the top tank and over flows through the overflow tube?

Actually it’s expanding from the heat building up.
And or air from boiling.

[ModelTWoods]

Jonah, its not the clog itself that causes the overflow. The clog causes the water to flow through the radiator in a volume NOT sufficient to cool the water below the boiling point. Boiling water, expands and as the water expands, it has to go somewhere, and that somewhere is out the overflow tube. If your overflow tube was clogged, the pressure built up inside would force the water to find someway to get out, either at the cap or some weak spot ot soldered joint in the radiator.

[DanTreace]

If the coolant comes out the overflow tube, when you have just filled the radiator or topped it off, sometimes that is just excess coolant.

The top tank will normally hold what is necessary, that tank is also the ‘expansion’ space needed for the thermo-syphon to work.

The normal level is about midline at the Ford Script on the shell, just over the baffle plate. Too much coolant will spill out the overflow tube until balance is made. Too little coolant will develop to steam as the volume of coolant is unsatisfactory, so steam will exit the overflow tube.

[DickC]

I have a "barn find" that I went through prior to driving. It had been in a barn for about 20 years and needed a bendix, new ball cap bearing, and rear brakes. Changed oil, installed new bands and tested driving it on several local trips. Took it on a recent club tour. No problem until we had a rest/catch up stop. Came out of the rest room and several people were waving at me to get to my car. Opened the hood and a steady stream of anti freeze was spewing from a corner of the radiator. Opened the filler slowly and released the pressure. Found that "dirt daubers" had blocked the overflow tube and allowed pressure to build up and find a weak spot in the radiator. Ran a wire into the over flow tube and cleared the problem. No problem since.

[RichardG]

JONAH, TO ANSWER YOUR QUESTION WILL MY RADIATOR BUILD UP AND LIT COOLANT RUN OUT THE OVERFLOW, YES--IF THE COOLANT CANNOT RETURN TO THE BOTTOM FAST ENOUGH IT NEEDS TO GO SOMEWHERE, THE OVER FLO IS DOING ITS JOB, SOUNDS TO ME LIKE YOUR RADIATOR NEEDS WHAT IS CALLED A RODDING OUT, THAT'S WHERE THEY REMOVE THE TANKS AND PUSH A ROD THROUGH THE TUBES, CLEARING THE BUILD UP IN THE TUBES THAT RESTRICTS THE CIRCULATION OF THE HEATED WATER BACK TO THE BOTTOM BACK TO THE BOTTOM OF THE RADIATOR, RADIATOR SHOPS ARE GETTING HARD TO FIND AS RADIATORS ARE BEING MADE OF ALUMINUM AND HAVE PLASTIC TANKS-AND ARE TOSSED AND REPLACED--GOOD LUCK===

[Scott_Conger]

Jonah

one of the very hottest tours I ever ran on was a National Tour in Minnesota. It was 105F and 90% humidity. At several stops I saw a T driven by an elderly gentleman, with several equally seasoned ladies riding with him. At EVERY stop, he topped off his radiator and said "My Lord, I've never driven in such heat!". I advised him to QUIT FILLING the radiator and just let it run out as it wanted to and only fill it if it dropped to the bottom of the "FORD" embossment on the front. That evening he looked me up and told me that in 35 years of ownership of the car, he had obviously never known where the coolant level should be and since the car had never been taxed in such heat, he'd never experienced overflowing. Both he and the ladies were petrified that they'd be stranded. He finished the tour without having to add another drop of coolant and thanked me profusely at the end. You're never too old (or young) to learn something new.

This may not be your case, but like a few others have cautioned or opined, it is something to consider.

[Jonah D'Avella]

Ok, when I fill it to the top, it lowers until I can see the tubes in about 10 miles.

[Michael Peternell]

Ok, when I fill it to the top, it lowers until I can see the tubes in about 10 miles.

Yup Jonah that's a problem. In your situation young man I'd give the vinegar thing a whirl. Can't hurt a thing and who knows you might get lucky.
I'm in the recore/new side on this but I so appreciate your intense interest in the hobby! I'm about as new to it as you are and love it also.

[Kerry]

Sounds more like a leaking head gasket, fill with water, start and see if you are getting bubbles.

[Steve Jelf]

Ok, when I fill it to the top, it lowers until I can see the tubes in about 10 miles.

I don't like that. When you overfill like that, the car should just barf out the extra coolant it doesn't need. The level shouldn't get all the way down to the tubes.That suggests to me that unless you have an undiscovered leak* somewhere, you have coolant boiling out. Better go back and study some of the suggestions of what to do for overheating.

An undiscovered leak could be a leaking head gasket, as Frank says.

[Ruxstel24]

Sounds more like a leaking head gasket, fill with water, start and see if you are getting bubbles.

Yep !! That’s cheaper than a radiator.
If you see bubbles on a cold start within a minute or two....head gasket is probable.

[Pep C Strebeck]

Ok, when I fill it to the top, it lowers until I can see the tubes in about 10 miles.

At what point on this illustration do you fill it up to? What point do you consider to be the top?

[Duey_C]

I shouldn't. The upper water level to me is at the overflow tube.
I'm with Mike and some else that suggested a vinegar wash or a baking soda wash out just to see.
New radiators truly are magical yet there are a few out there doing their work as intended a hundred years ago without much issue.
I got lucky 20 some years ago with a scaled up swap meet rad.
A baking soda wash out my certainly not work. Like the old Dyke's book says: One method....

[DHort]

Jonah

In my new Berg's radiator there is a metal plate on top of the tubes. I do not know the purpose of this plate, nor do I know how high it is placed above the tubes. Maybe it is just a baffle to settle the fluid down. If I fill the radiator with 1 inch of antifreeze above this plate, I know there is too much in there. I check this with a wooden dowel or just a stick I pick up off the ground. After driving there is usually 1/2 inch of antifreeze above that baffle. So that is where my radiator likes to be. Others may be different. I am sure if you called Gerry at Berg's he would be happy to explain what you should see and how to do it. Very nice guy.