Blowing water out of radiator cap

[BillLee/Chandler, TX]

Given that the cooling system on a Model A is non-pressurized and that there is an overflow tube from just under the cap, why do we occasionally hear and see of coolant being expelled from the radiator from the radiator cap?

On my A, the only time I ever had that problem was when the overflow was plugged. With the overflow clear, if I fill the radiator a bit too high, it will blow a bit out of the overflow tube until the level gets to a "proper" level, but certainly not from the cap.

[Kurt in NJ]

Bad cap gaskets, poor fitting reproduction parts, damaged radiator necks from overtightening motormeter bases.cracked brass in rad neck.

With my car if I can see the coolant above the baffle it is too full, when it spits out the excess the level is just below the baffle --there it stays.

[Jack '29 Sport Coupe]

If I see water in the radiator on mine, it's too full. The way I test to see if I have enough water is to stick a battery filler in the radiator and move it to the side. If
I can suck water with the tester, I know it has enough. I used to stick a flashlight down to see the water. Using this method I sometimes had to shake the car to try and see water sloshing around, lol. The battery filler is much easier. If it doesn't draw water, I add water in small increments until it does. JMHO

Jack

[bluesman31]

I had this problem today on my first long 20 mile run, doing 45-50 mph up and down moderate hills.. the car spit a small amount of coolant and the thermo quail went from 20% red to 50% red.

So is the correct level to fill the radiator just to the baffle you can see when you look inside the radiator? For my radiator this is about 3 or 4 inches down from the top of the radiator.

Does the fact that water is doing out of the cap and not out the overflow tube indicate that I need to replace the 2 radiator cap gaskets?

[Bruce Adams]

Quail Incontenance !

Actually, the water pump pushes more water than the radiator will flow at high engine/water pump speeds, so there is a back up at the top tank which forces its way out the cap.

[bluesman31]

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Do I need to replace the radiator cap gaskets or will the cap overflow even if the gaskets are perfect? I thought the overflow tube would handle any excess water issues?

[eagle]

Your car will figure out where the correct level is. Fill it up and take it for a good hot run, it will find its own level. On mine I add a quart every 6 months, it dumps water for a few miles and then all is well. I use 50/50 antifreeze.

[kp]

Common sense,the radiator is clogged ,not allowing the water to flow through fast enough.My over flow tube was clear ,drive about 5 minutes at 40 mph and blow off radiator cap,new core and all is well.

[TinCup]

My father who is 92 and drove his first Model A when he was 12 laughs when I tell him I drive my car 45-50 mph. He says that the road conditions of the day were such that if you could drive 30-35 mph on a road you were doing good. Yes they could drive the cars 40-45 but with narrow gravel and partialy paved roads it just wasn't safe. Only when they went to town on the weekends would they ever encounter roads good enough for higher speeds. I got this story when I was fighting my own overheating issue. His advice was just slow down and you will be fine. I think at higher speeds if the radiator is partialy clogged it will back up and cause your radiator to force water out the overflow or wherever it can.

[FL&WVMIKE]

Billlee/Chandler,Tx. .....................
Kurt in NJ stated the bad gasket or cracked radiator neck. Any other reason would be stopped by a good gasket. You should not have any way for water to come out of the radiator cap.
You could, now, have a gas cap for a radiator cap. That would surely leak.
MIKE

[Purdy Swoft]

Quail caps have two gaskets and can be twice as hard to stop the leaks because of this. These caps are known for ruining the radiator necks. Fifty fifty antifreeze is much much more likely to leak at places that pure water or water with waterpump lubricant won't leak. Fifty fifty antifreeze doesn't cause a model A to run cooler in the summer, just the opposite. When I used the coupe as an every day driver, it was necessary to run antifreeze in the winter. The winter temperature is not as severe in AL. as it is in MN.. I only used one gallon of antifreeze per two gallons of water. It was a real pain in the winter haveing to run a one to two mix because I constantly had to check and add more antifreeze. Antifreeze doesn't work well on unpressurized systems in hot temps.

I've never owned a new old stock model A radiator . Most originals won't flow like they did over eighty years ago, NO matter what. Though they cool good for me, it has been said that the repro radiators don't flow as well as a new original because of difference in tube size.

The unmodified water pump pushes more water than any radiator that I've used in the past 52 years can flow, If the cap isn't sealing properly, you will see droplets on the windshield and hood, especially under acceleration. If the cap actually seals, rare in many cases, the excess will go out the overflow pipe. Remember coolant expands when hot and with the super action of the water pump,If the coolant can't flow through the tubes of the radiator fast enough, its got to go somewhere.

Ford wanted to be sure that his cars ran cool. I don't have documentation in front of me at this time but I have read that the first pumps had five vanes instead of three like the pumps now have. The early pumps pushed way more water and was changed to slow the overflow. Snyders use to recommend in their catalog to grind some material off the impeller of the water pump to reduce the action. Too bad that nobody offers an impeller that needs no mods. I've been grinding the tips off my impellers for at least 40 years with good results. Some of the so called experts will frown on this practice, That is the kind of garbage that I just ignore. Some like to say bandaid fix. If it helps the problem and still cools, it just makes common sense. Some use thermostats to calm the flow. I don't use thermostats in my model A's because they can stick closed and ruin an engine. With the corn fuel that many of us are forced to use, a thermostat may help cause the engine to run hotter so it will burn the weak unstable fuel. A good working ,inside temperature gauge would be of benefit if you run a thermostat. I allways remember what a hellish job it is to remove a stuck thermostat from a hot engine, side of the road in the hot summer and still don't use them in any of my model A cars.

[BillLee/Chandler, TX]

Originally Posted by FL&WVMIKE

Billlee/Chandler,Tx. .....................
Kurt in NJ stated the bad gasket or cracked radiator neck. Any other reason would be stopped by a good gasket. You should not have any way for water to come out of the radiator cap.
You could, now, have a gas cap for a radiator cap. That would surely leak.
MIKE

Everyone: please check the date of the original post, it was almost two years ago.

But to answer my own question, and to chime in here: Every Model A radiator has a built-in gigantic leak. It's called "the overflow tube". It is a tube 3/8"OD that has a hole in the middle FAR LARGER than any leak could be with a faulty gasket . IMHO, KP's "common sense" is the answer: a clogged radiator and possibly coupled with a clogged overflow tube. There just isn't any way that a gasket leak could overcome the built-in leak of the overflow tube.

From my personal experience: when I got my car, it would spit water from under the Quail. Found out a month or so later that the overflow was totally plugged, probably a mud dauber nest. After cleaning the overflow, no more spit from the Quail. Fill the radiator, drive it, let it find its own level by dumping excess out the overflow, and all is cool (pun intended!).

[bluesman31]

The car cools just fine, and only overflowed a bit and then stopped. I will stop over filling the radiator, verify other overflow tube is clear, and replace the worn out quail gaskets. Thanks for the tips.

[Vern]

Try replacing the quail gasket with an "O" ring. That stopped my repop cap with the motometer spitting.

[CarlG]

I put a couple of the brass washers intended for the gas gauge, glued them in with some gray silicone sealant with the washer on top of that.

Didn't think about the O-ring, but that would work as wlll as long as the cross section was large enough to get a good seal.

[bluesman31]

How do you replace the gaskets on the Quail? I have replacements for the red fiber one on top and also a softer one that goes below it?. There are 2 screws , hex heads I think?

[Purdy Swoft]

I used the high temp orange colored silicone to hold the gaskets in place on the thermo quail on my daughters 31 coupe. It no longer spits out droplets on the hood and windshield. Its been holding for several years but was a real pain beforehand!!! Ive never wanted another accessory type radiator cap. She loves it though.

[bluesman31]

So do you just scrape it off and install the new one?

[sconnors]

Originally Posted by Vern

Try replacing the quail gasket with an "O" ring. That stopped my repop cap with the motometer spitting.

Where did you get the "O" ring? I ordered a gasket from Snyder's but it's too big, and my pickup has a motometer too.

[Purdy Swoft]

Originally Posted by bluesman31

So do you just scrape it off and install the new one?

Its been a few years but i'm sure that I cleaned it up to give the new gaskets and sealer the best chance oif working. It seems like I remember that improoved tabs came out sometimes in the ninties for the quail caps. Thats when I did mine. my daughter now has it.

I see a repair kit in Snyders catalog that has the gaskets tabs and screws. Look on page A-174 The part number is A-18360-BRK The price is only $7.35 . If you don't have their catalog but you are interested in this kit , you can call them toll free at 888-262-5712