Radiator Foaming Under the Cap

Smitty

Smitty

Well-known member
I have been experiencing radiator foaming and throwing coolant all over the car when I climb hills.

Details:
* Not the head gasket - already checked the decks and replaced the gasket.
* Not overheating 140-deg.

* Not over filled with coolant.

What the heck is going on, this was a new radiator in 07. The car did not always do this....

Thanks, Steve
 
had you put radiator flush in recently and not flushed out entirely? run it with the cap off look for air bubbles,did you do anything recently that could of caused this problem.
 
I will fill in for Bill W, "drop a loosely fitting nail with a large head in to the over flow tube, it will stop the water from splashing out and won't preasureize it"
 
Have you done any cleaning or changed to a different type antifreeze? How is the gasket in the cap? Did you change the water pump? How not over filled is the water level?
 
What's different is always where I start. Did I just flush the radiator? Have I changed antifreeze or water? If you climbing hills your rpms are up and the waterpump could be cavitating and causing the foaming. The nail trick works. Unlike my buddy who put a golf tee in his overflow and it swelled up and sealed off the overflow which gave him a pressurized radiator. When it overheated he was in for a big surprise when he opened up the radiator. Good luck.
 
John Duden said:
I will fill in for Bill W, "drop a loosely fitting nail with a large head in to the over flow tube, it will stop the water from splashing out and won't preasureize it"
Click to expand...

John
Thankyou Bill # 2 ( lol ) ! Bill will get a laugh out of this one ! But you know what, it really works !
Wayne
 
Foaming under load (uphill, high cylinder pressure) is almost always some type of gas entrainment in the coolant, whipped by the pump. Combustion gas is likely still getting into the coolant despite your deck/head flatness check and a new gasket. You could have a small block or head crack somewhere, not visible to the eye.

Try using a coolant combustion gas tester. This one is NAPA pn# 700-1006 and comes with a hand-pump vacuum bulb to draw radiator air into the tube. There are others available, some require an engine vac connection.
fluid.jpg

Failed! Yellow indicates presence of carbon monoxide (a combustion leak).
 
If the radiator is gushing out from under the cap it should not be as a result of the overflow tube?? Could it be air trapped in the system? Does it with coolant and also with plain water.
Am I correct in the nail would only improve on loss through the overflow tube? Or is it pulling air through the overflow?

Steve
 
I actually have that NAPA kit, tested the system a while back. Perhaps time to test again.
 
No matter what, water or bubbles should not leak from your radiator cap. You nedd a better radiator cap gasket.
It should seal well enough to send anything out the overflow.
That might be your only problem, if it is not overheating.
MIKE :) (mikeburch)
 
I had wondered about whether the cap could be at fault. I am a bit confused on that one. I have been told that the radiator cap is not a tight seal and thus not the problem.
This is a reproduction cap, a fairly good one I think. I have purchased a new gasket (not yet installed) but it seems rather stiff...
Should the cap want to fit the filler rather snug? It has baffled me as to why the coolant is not running out the overflow tube rather than blowing out from under the cap.
Steve
 
The cap should seal on the radiator neck and any overflow should go down the pipe and not on the hood.
I had a foaming problem and it turned out to be all of the old grease in the radiator. I couldn't get all of it out until I took it to the radiator shop. Works fine now.
 
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I chased a similar problem with an NON Ford. Spewed every hill or when I accelerated. It was the gasket on the cap.
 
Both my 33 and 34 Ford do this. I bought a chunk of red plummers rubber from the hardware store and it is a lot thicker then the radiator cap gasket they come with. Regardless, it will still spew a little foam out from under them (I have the 3lb pressure fitting supplied by Skip on both the overflow tubes, so the cooling system will build slight pressure).
I always wondered why it was foamy. My Dad's 34 and 36 Ford also get foamy. None have over heating problems.
 
Also remember that some brands of antifreeze foam more than others. I have read that Prestone is bad but Sierra works. I don't have personal experience comparing the two. When Prestone blew all over my windshield I changed to water pump lubricant. One of the good things about living in Southern California is that you don't have to worry about antifreeze.

Charlie Stephens
 
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