radiator splashing

German guy

German guy

Senior Member
When I am lugging the engine on a hill...for example...unable to down shift to 2nd gear without slowing down a lot, double clutching, and grinding gears only to end up lugging in 2nd because the gear change took so long... sometimes I get anti-freeze splashing out of my radiator cap. The car is not over-heating at that point. What causes that burst of pressure that is expelling anti-freeze? I have found that I need to keep the fluid level so low that I can not see or even feel it when I stick my finger in the radiator. That reduces it...but it still happens when I hit the right situation. I have thoroughly flushed the system and the car does not seem to be over-heating.


Any suggestions?
 
I use an extra thick O ring on my radiator cap to seal it and keep the coolant from splashing out. The water pump impeller can push extra coolant when you rev the motor to down shift. Or, as Canton said, you could have a blown head gasket. You can grind the corners off the water pump impeller to reduce it pumping ability. The best time to downshift is before you need to. Try to anticipate the need.
 
The normal water level is below the baffle. So it sounds like part of your problem is overfilling. I stand inside the bumper and rock the car sideways, to check my level. You can usually just barely see it sloshing.
 
Rule out a head gasket leak by testing for combustion gasses in the cooling system.

An auto parts store should have a test kit or drop by your local mechanic and have them test it.

Have you checked the torque on your head nuts?

Regardless of what is causing this you shouldn't have coolant coming out from around your radiator cap. You have a bad gasket on the cap.
 
From your description of the problem, I'm guessing you have a fancy split Flying Quail or Moto-Meter radiator cap. These caps are attractive, but are notorious for allowing hot coolant to surge out under power demands, such as you describe. I'm also guessing your radiator doesn't have the all-important baffle in the upper tank. Without that baffle to re-direct boiling water back down through the radiator, the coolant follows the path of least resistance and heads for the radiator filler neck. The result is a messy overflow onto your hood and windshield. You know all about THAT, don't you?!?
Yes, one way to help curb this problem is to keep the coolant level a little lower than usual, yet not enough to compromise cooling efficiency. Do not fill the radiator to just below the filler neck. That's too much coolant. The level should be just above the top of the core inside the top tank, which is considerably lower than if the top tank were filled. As the water heats up, it expands and will exit wherever it can. Too much water/coolant exacerbates the problem. Once the water starts flowing out of the radiator filler neck, people often think the engine is overheating. Well, it WILL overheat if enough coolant is lost. What happens when the coolant in the radiator heats up and begins flowing out of the split radiator cap, is it becomes a self-perpetuating puking action that will only cease when the car is stopped for a while or if you can coast downhill for quite a distance. Try putting on a regular factory-style flat cap in place of your fancy two-piece radiator cap and see if the problem persists with water rushing out of the overfill tube. If it does, then there are other issues to contend with, such as a weak radiator core (especially if it is only a two-tube core sold by J.C. Whitney) or a blown head gasket, as has already been suggested. I should think if the head gasket were blown, however, you'd notice a drop in performance and perhaps misfiring. Any of that going on with your car?
Marshall
 
old31 -
Thanks for the thumbs-up! 'Been there many times in the past during my Model A learning curve. I speak from painful (and messy) experience. :( There's almost nothing better an owner can do for his Model A and his own mental health than to ensure his car has a good radiator with the baffle in place. The poster's problem with a splashing radiator has come up here time and time again and the cause can almost always be traced to a poor or clogged radiator without a baffle to re-direct the surging water. Money spent on a three-tube radiator with baffle is about the best money that can be spent on our old cars to ensure happy motoring experiences. A number of pesky problems instantly go away with such a radiator - after one gets over the sticker shock of paying for the radiator. :)
Marshall
 
One of the things I love about the internet is chances are, if you're asking a question, someone else is wondering the same thing.

My car (31 Victoria) was doing the same thing. When the engine was under load, antifreeze would foam and spew out from the radiator cap. I was troubled by this, particularly since I just replaced the radiator with a brand new Brassworks "extreme touring" one, and while everything was opened up, flushed the cooling system out. (I changed out the cylinder head, water pump and head gasket with a Best brand one last year, so all of those were good to go.)

Anyway, I figured I'd try out changing the cool Motormeter radiator cap with the "stock" Model A one. Kind of boring, but I doubled up the gasket and put it on. It was tight, but that's the key.

Long story short...no issues with foaming. I filled the radiator up with coolant, just above the baffle, and had a couple of drips come out of the drainage tube (as it's supposed to) after driving. Otherwise...it didn't look as cool, but the stock radiator cap with doubled up gaskets worked great.
 
I pulled the fancy 'quail' and discovered that the mouth of the radiator is very bent ...threads for the stock cap all bent out of shape. I am trying to get it into a flat surface to mate with the washer under the 'quail' which seems to have a good tight fit otherwise. I that fails it may be that the 'quail' has to take flight. Also..it is the original radiator and has no baffle at the top to direct ant-freeze to the over-flow tube. Over-heating is not a common problem here in Germany. Seems that little things make a big difference in these cars.
 
I have the original radiator in our ‘30 coupe. It is sitting at 69,413 original miles and I drive it 2-4 times a week. The mention of a baffle has me baffled… since it is original and 94 years on the road, was it built with a baffle?
Baffled, but so far not buffaloed. Thanks in advance for the input.
 
SHEC said:
I have the original radiator in our ‘30 coupe. It is sitting at 69,413 original miles and I drive it 2-4 times a week. The mention of a baffle has me baffled… since it is original and 94 years on the road, was it built with a baffle?
Baffled, but so far not buffaloed. Thanks in advance for the input.
Click to expand...

Yes, it had a baffle. When in place, you can't see the tubes in the top tank, they are under the baffle.

And Ford said to gently bend the overflow tub back toward the back of the filler neck. I insert a round Phillips screwdriver in the overflow tube and lift a bit, take the screwdriver out a little, lift a bit more, repeat until the overflow is curved toward the back.
 

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I am assuming you know the cooling system is non-pressurized so the only way coolant can come out of the cap is because of a poor seal. It is also possible the overflow tube is too short. It should be above the baffle and almost near the bottom of the fill neck. The normal operating level of the coolant in most Model A's is usually at or slightly below the baffle. If the overflow tube has been shortened enough the coolant can escape while driving causing the engine to run hot or overheat. This becomes very obvious when climbing a hill at low speed.
 
rackops said:
Anyway, I figured I'd try out changing the cool Motormeter radiator cap with the "stock" Model A one. Kind of boring, but I doubled up the gasket and put it on. It was tight, but that's the key.

Long story short...no issues with foaming. I filled the radiator up with coolant, just above the baffle, and had a couple of drips come out of the drainage tube (as it's supposed to) after driving. Otherwise...it didn't look as cool, but the stock radiator cap with doubled up gaskets worked great.
Click to expand...

I had issues with the 'locking' radiator cap also but liked the looks of the Moto-Meter so I installed a Moto-Meter in a repro stock cap. I use a ⅛" thick cork gasket that I cut. The cork gasket seals much better than the hard fiber replacement gasket the vendors sell. Best of both worlds.

542111
 

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