Water from radiator cap cold

KMeredith87

KMeredith87

Senior Member
So my engine is a fresh rebuild, about 300 miles on it. I find this odd and have no explanation for it...when my tuck is relatively cold, running for 5-10 min maybe it has had a recent issue of throwing water out of the radiator cap. Tends to be a little foamy also. However, once it's been running for a while I have zero issues. I can run it up tp 65 mph (no overdrive or special ******) and have no issues and no water out of the cap. Thoughts or explanations?
 
If you are filling radiator to the top cold, it is over-full when heated up and blows the excess out the overflow. This is normal for cars with open systems/no overflow return tank system.
If it establishes a stable level down some from the cap and above the core and stays there through several runs, all is fine. If it continues to drop then worry about trouble shooting.
 
I've retorted the head twice since I built the engine so not sure that is the problem but I will definitely do it again anyway. However, I am aware of the radiator finding it's own level, no issue there as I know where it likes to be. Only issue I have is the water blowing out and don't know why and it makes no sense to me that it would happen when the engine is colder and turning slower. Seems that it would be more likely to happen hot and at high speed...
 
KMeredith87 said:
I've retorted the head twice since I built the engine so not sure that is the problem but I will definitely do it again anyway. However, I am aware of the radiator finding it's own level, no issue there as I know where it likes to be. Only issue I have is the water blowing out and don't know why and it makes no sense to me that it would happen when the engine is colder and turning slower. Seems that it would be more likely to happen hot and at high speed...
Click to expand...

You said you were getting foam. That means air is getting in the water. Most of the time that means head gasket or crack in block.
 
Good to know, didn't know that bit of info, thanks! I had the block magnafluxed and check for cracks prior to building it so hopefully the block is good. However, now that I think about it I have noticed some white substance that dries and gets crusty at the head seam on the drivers side of the block. Head gasket? No water in the oil...
 
i agree with georges responses
are you running a t-stat????
you say it throws the water out the cap is the cap seal bad?
or is it coming out the over flow?

i would keep rechecking the head torque cold...
 
The cap seal looks good, I did check that first, though it is a motorcycle meter cap. No t-shirt, just standard cooling system which I flushed and cleaned recently. Seems to work fine and cool just confused about the random dumps of water. Definitely from the cap though not the overflow. I'll retorque the head and again see what happens. I do have a modern style head gasket on it at the moment as its a sender 6.0-1 head...
 
i have found many retorques are required on the moderns.. do you have a stat???
if the cap is sealing properly it should not come out of it but would come out the overflow..

as a last resort you can always do a leak down and hydrocarbon check with dye...
 
Sorry, t-shirt was supposed to be t-stat. No t-stat in it. The only time that I see foam is when it comes out of the cap. When I check the water after a drive it's just water in the top tank, no foam.
 
I found that my foaming was due to the water pump moving water fast enough to churn it up in the top tank of the radiator.

I took a different route to get rid of the problem and eliminate the daily check the radiator level task.

I bought the $10 overflow kit from AutoZone, hung it with removal wire ties from the radiator support rod on the drivers side and ran the hose down to the bottom of the overflow tube. Put a solid sealing o-ring in the radiator cap, filled the radiator all the way up and have not added water all summer. (I did it this way to shut the "others" up about not being the way Henry designed it.....It is not permanently mounted and requires no tools to remove.)

With the upper tank full I do not get the foaming on water (with wetter) or with antifreeze. And, every time it cools down it sucks the water back into the radiator. I looked in the radiator yesterday and the water was all the way up in the neck, at the top of the overflow tube.
 
I think the coolant problem has been covered, but I'm concerned about the 65 MPH on a fresh engine, and especially with no overdrive.:eek:
 
Tom, I'm not completely nuts, it's a fully inserted engine and I was only there for a few seconds to stretch her legs. I built the engine to look at stock as possible but be as modern as possible inside. (I went a little over board I won't lie)I could be completely wrong here but I am not overly concerned being that it is inserts and the rings seem to be completely seated as I have no smoke and no oil consumption. But then again, I am still a dumb kid! :)
 
65 with 300 miles and no pressure oiling is asking for a spun main, and a scored piston on 3or 4.

You said you are getting foam when cold but not when hot. That kinda levies out the water pump. It would be the same hot or cold. Those new gaskets take many torquing s before they hold.
 
This is exactly why I come and ask you guys questions as you set me straight. I will keep my foot out of it until I hit the 5-600 mark. I guess I am too used to modern cars and jets. That and being impatient and too excited to have to truck running again.

I will keep torquing my head after a run and total cool down and see if my problem goes away. Thanks for the help!
 
If you're still leaking at the cap, "might" be where the neck is soldered to the top tank. It's an EASY, "on the car" repair.
Bill W.
 
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