C2 Cooling System

[Ken K.]

I just got done detailing a 1967 327 engine compartment. I had the radiator and hoses out of the car. After installing, I refilled the system, (50/50) by poring it into the expansion tank. I started the car and let it run for 10-15 mins. waiting for the thermostat to open, so I can "top off" the system. It never happened. The coolant in the expansion tank never dropped. The radiator was still cold. I remove the top hose to check the thermostat, it WAS open. So what going on? If the thermostat is open, why isn't the fuild being pumped through the radiator? Do I have a "air pocket" or is something wrong with the water pump?
Thanks Ken

[jordan grant]

Re: C2 Cooling System

Hi Ken,Scroll down farther on this page,I remember last week or so someone addressed this very problem in detail.

[Duke W.]

Re: C2 Cooling System

Yes, you might have a big air pocket. The system should be filled SLOWLY.

The route from the expansion tank to the block is through the heater return hose to the water pump inlet and air in the block has to vent through the heater hose on the manifold through the core and back to the tank. The radiator vents through the vapor vent at the top of the radiator to the top of the expansion tank.

The trick is to just poor a little at a time and let it drain from the expansion tank so the air in the block can vent back through the tank.

There will always be some air bubble, but as long as the level is sufficient to cover the pump inlet, the pump should be able to pump coolant through the bypass circuit, and when the thermostat opens, the air will vent to the radiator, and then to the expansion tank via the radiator vent line.

Duke

[Ken K.]

Re: C2 Cooling System

So should I drain the system by using the pitcock on the radiator then start over? Is there a better way to drain the system too help get the air bubble out? Ken

[Michael W.]

Re: C2 Cooling System

Just remove the thermostat housing and fill the block from there. Replace, top up the expansion tank and that should do it.

[Duke W.]

Re: C2 Cooling System

Or you could drain coolant from the radiator until the expansion tank is empty, Then SLOWLY add coolant a little at a time and wait for the tank to empty as it flows into the engine and radiator. Once the tank won't empty, fill it about halfway, then start the engine. When the thermostat opens the tank should empty. Slowly add coolant until it won't take anymore and is about half full. Bring up the revs to about 4000 to see if the pump will pull anymore coolant from the tank and add if possible.

After it cools to ambient temp, check the tank and fill it to about half full. Keep checking it after it cools from the next couple of heat cycles until the level stabilizes.

Duke

[John H.]

Re: C2 Cooling System

I've done this countless times, with no problems - the recipe is to fill the engine through the thermostat opening in the intake until the coolant level comes up to the top, then install the thermostat, gasket and housing/upper hose, and continue filling through the expansion tank until the tank shows half-full. Leave the cap off, fire it up and run it until the thermostat opens (upper hose gets hot right away), let it run for five minutes, and shut it down. When it cools, top up the tank to half-full, cap it, and you're done.

The air in the block has to have a place to vent as it's displaced by coolant when you fill; if there's no place for it to go (or the path is difficult), you wind up with a short-fill and air pockets.