I have a 95 ford lightning I just got the motor back from being rebuilt and when I first fired up the engine for the first time coolant shot up out of the radiator fill opening. If the motor is run for very long with the cap on the pressure built up on the upper radiator hose is pretty extreme it is not enough to bypass the cap but as soon as you let the pressure off of the cap it blows antifreeze into the overflow tank I have tried un hooking the water pump to see if there was any issues with it such as being the wrong rotation and that test yields the same results. I guess my next step it to do a leak down test on each individual cylinder and see if it is a head gasket issue. There is no coolant in the motor oil also. I just wanted to see if anyone else has run into this issue and had any tips.

Thanks

 

Pressure is normal in the cooling system. It's what raises the boiling point of the antifreeze to keep it from, well, boiling while it's inside your engine. It's normal that when you loosen the RADIATOR PRESSURE CAP that coolant will flow into overflow tank. The pressure cap is what regulates the pressure in the cooling system, meaning if it gets too high, it will allow coolant to flow into the overflow tank. When the pressure becomes too low, often related to low coolant levels, the coolant in the overflow tank is siphoned back into the system via vacuum that's created inside the radiator due to the low pressure.

Unless I'm misunderstanding something, you don't have any problems with your cooling system.

 

I have to make a correction to my previous statement after further testing and it seems like it is getting worse the pressure is excessive enough to bypass the radiator pressure cap, this is occuring with the motor cold and after running about 20 seconds. Also it seemed like I could smell an odor of raw fuel in the cooling system after opening the radiator cap?

 

Sounds as if you may have cylinder compression leaking into your cooling system and pressurizing it. That could also lead to the "raw fuel" smell you've noticed.

 

Is this a sign of a leaking head gasket or cracked or warped head?

 

Your guess is about as good as mine until you pull the affected head off and check it out.

 

Ah, yes, well in that case, I definitely misunderstood.

I'd recommend a compression test to start, then a cylinder leak down test. If one of the cylinders is leaking in the manner BigBlock describes, that will give you a definite answer to to which cylinder(s) it is.

 

I'd recommend taking it right back to the builder before anymore time elapses.
I also recommend finding a new builder because if they were any good they would have caught that before sending it home to you.

 

I agree, you should go back to them ASAP. The more time that goes by, the less helpful they'll be. Also, if they didn't do a good job the first time, you should find another shop.