Radiator issues

[steve welder]

My CJ has a recently rebuilt engine and also a new radiator, whats going on is the cap is not sealing on the rad neck. The bigger issue is with coolant about an inch below the top of the neck coolant is being pushed out of the radiator and continues to do so until right below the top of the top of tubes. The coolant is full of bubbles and when reving the engine will come out of top of radiator
There is no white or blue smoke coming from exhaust, engine oil has no water in it, spark plugs look good, engine runs good, compression is 130 in all cylinders
I cannot get my radiator tester using the adapter to seal so I cant pump up system. Im at the point im going to drain coolant remove rad and hook up something to pressurise the block and see if will maintain some pressure
Im thinking the head has a crack or the head gasket in one cylinder is leaking compression into cooling chamber
Any thoughts/ advise are greatly appreciated as im bummed out of this

[bmorgil]

Steve, when you say bubbles what are you seeing? Large burps or small and many? If you are leaking water into the motor or out of the motor you will eventually see it show up in the oil, exhaust or floor. The radiator does not fill to the top. It should be about an inch down. You need room in the radiator for the water to expand when it heats up.

What head gaskets did you use? Did you re-torque the studs after a heat cycle?

I agree with your approach. Find a way to pressurize it, or see if you can fix the pressure checker and find out for sure.

[steve welder]

Small and many bubbles, so much so I cant see the coolant
The head was already on when I got the engine back as I had the rebuilder assemble the engine
Im going to check all the head bolts asap. I have to put some air pressure into block, years back I had my 383 ready to be dropped in the car and started. Before I put the engine in I rigged something up and put some lower pressure air into cooling system. To my surprise it wouldn't hold anything, than I noticed a hissing noise, one of the heads was cracked
Either way I will get to the bottom of the issue, Thanks for advise

[bmorgil]

It is concerning that it wants a lot more room and is pushing the water that hard. If it was full of air, it will push the water out until the air is cleared from the motor and hoses.

I think it is much easier to find the leak and to pressure check the system if it is full of water. The pressure will come up much quicker and the water will get pushed out wherever it is leaking.

It should have studs not bolts. Bolts will crack the block.

[steve welder]

Thanks B, I managed to get some pressure in cooling system, anti freeze is in #3 cylinder, so im hoping head gasket or a head, as long as block is good im a happy person
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It kind of makes sense there was no white smoke from exhaust, as the rad cap is not sealing. so the cooling system wasnt building up pressure. Time to pull the head and hope for only a bad head gasket or head