losing water

[econofan63]

I have a 250 in my econoline truck,had a problem now for a while where it will spit all the water out over a long jouurney, it has a new bigger radiator, new rad cap,new water pump and thermostat. compression is good on all cylinders so i asume the head gasket is good, also done a chemical test to see if any engine gases are leaking into the coolant and its clear. but still im dogged by this, the water will blow by the cap and out the overflow, the temp reads normal, are these engines prone to air locks? could that be the problem? the new rad cap is 16Lb is this strong enough?
today i totally flushed the system which was pretty messy (the water was red rust colour) the refilled and added coolant engine flush, run it up the drained off again and filled with coolant and it still spat the water out the overflow after idleing for a while.
any ideas??????

 

[fordconvert]

Does the overflow go to a tank or is it just a tube? If there is no tank the level in the radiator is typically down an inch or two from the top. How far does it drop after it burps? What happens if you dont refill it will it stay there? That was typically how it worked with older systems.

 

[econofan63]

the overflow is just a tube, if i go on a run the level drops well below the fins and takes quite a bit to top up,

 

[fordconvert]

Well below the fins does not sound right, on my older stuff it tends to be just above the fins.

 

[ludwig]

You need to wash/purge the system until the water runs clear. There are a couple recent strings about this topic and you can find them easily with the search function.

If you are worried that there is air trapped inside the block or somewhere, run the motor with the cap off until it heats all the way until the thermostat opens and keep running it. Watch in the radiator filler to see if bubbles or a large pulse of air comes through the radiator. Keep filling so that the fins are submerged a 1/4 or 3/8 inch. Be sure to leave a little air in the radiator. That is your cushion to keep the water from being pushed out there. If there is no air in the radiator and you have a bubble somewhere else, the water gets pushed straight into the overflow tube.

I like to push the accelerator. It pulls the water level down. Sometimes that will get an air bubble out, but mostly it makes me think I am doing something useful.

Some coolant loss is not unusual. These are not sealed systems and you were supposed to check the water level as part of the regular maintenance.

Beyond that, there are radiator water reservoirs available to catch the overflow so it doesn't fall on the ground.

 

[BIGREDRASA]

An inexpensive Coolant Recovery Kit will pay for itself in no time.

 

[ludwig]

http://fordsix.com/forum/viewtopic.php?p=404933#404933

Read this first.