Coolant push out of the radiator?

[pickupman96]

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.

[Desert1957]

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

[MilkyJoe]

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.

[Littletony]

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.