Coolant push out of the radiator?
 

On 89 gmc 1 ton keeps pushing all the coolant out. I will fill it up, put the cap back on and it will push all the coolant out of the system in a couple of days. Not just some, it will blow it all out. With the cap off and it running it will suck it down 3-4 inches and then spit it back out the neck. Im going to go put a new t-stat and rad cap on it right now but what else could it be and why. Thanks in advance for the help.

Re: Coolant push out of the radiator?
 

If its not overheating , possible Air Lock in the engine. Try disconnecting a heater hose off the intake manifold when you refill the radiator, might help to purge air out of the engine block, If No air comes out change the Thermostat.

Desert

Re: Coolant push out of the radiator?
 

mine did this, it was a combination of a bad thermostat, gummed up lines, and a lil air. I 'burped' it every other day, as I was going through coolant every other day.

Finally blew a head gaskt but the truck sat for 12 years before I started using it as a DD.

Put new head gaskets on, new collant lines, thermostat and radiator, truck cools perfectly now and hasn't used a drop

Hope this helps, remember K I S S. do the little stuff before it turns into a biggie like mine.

Re: Coolant push out of the radiator?
 

How old is the cap and is it the right cap for the truck? Mine was doing this two until I replaced the radiator cap. That was a little over two years ago and I have not had a problem since.