Tips for purging air from the cooling system

superheat6k

superheat6k

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Following several weeks with plain fresh water in my cooling system following the engine repair to make sure the engone was leak tight, this morning I added the antifreeze. I also have successfully repaired the broken spout on the expansion bottle.

But I am having trouble getting the air out - as the engine warms it is pushing considerable volumes of the coolant into the expansion tank, which it thens sucks back soon after shut down as it cools. I'm not losing coolant so I know it isn't going into the exhaust manifold and the spill over isn't severe enough to suggest exhaust is coming the other way (there is a hidden joint on the exhaust manifold to turbo charger connection).

So I suspect this is simply trapped air pockets which will considerably expand with temperature, whereas the liquid expansion is minimal.

So any tips for getting the trapped air to move into the header tank. There are a couple of vent valves but these are simply producing coolant flow without bubbles.

Thanks.
 
Do you have a calorifier? If so, there's a good chance that you have air in that. To get rid of it, loosen the top hose at the calorifier and if you have air in it, you will hear it escaping.
 
Provided that the engine is not overheating and you're not actually losing any coolant, I wouldn't worry about it. If all the valves are open, the air will eventually be pushed out, particularly when running at highish revs for a decent period. When the cold coolant level in the expansion tank starts to drop, you will know it's coming out.

Richard
 
Trev.

Make sure of 2 things.

First check that the vent pipe on top of the turbo snail to header tank is clear. But also make sure the bore size is minimal. Otherwise flow that should be going through the manifold will go straight to header tank.

Second check all the fittings, elbows, hoses etc at the back of the block into the turbo snail and the one from front of the manifold down to the intake elbow on the block.

Both of the above will reduce flow through the manifold which results in localised boiling

The manifold cooling is marginal. There's an SBMAR article about it.
 
burgundyben said:
Trev.

Make sure of 2 things.

First check that the vent pipe on top of the turbo snail to header tank is clear. But also make sure the bore size is minimal. Otherwise flow that should be going through the manifold will go straight to header tank.

Second check all the fittings, elbows, hoses etc at the back of the block into the turbo snail and the one from front of the manifold down to the intake elbow on the block.

Both of the above will reduce flow through the manifold which results in localised boiling

The manifold cooling is marginal. There's an SBMAR article about it.
Click to expand...
Ben That's interesting because I replaced the small vent pipe from the top of the manifold to the header tank as the old one was very rusty and weeping. I wonder if the new one has a larger bore. I can easily make a small orifice fitting to restrict flow. I think the ID was ~ 4mm, so I will reduce it to ~2mm.

But there is no pipe from the top of the turbo, just the drain / feed pipe to the lower rear.

I will also try removing the calorifier take off to vent that.
 
superheat6k said:
Ben That's interesting because I replaced the small vent pipe from the top of the manifold to the header tank as the old one was very rusty and weeping. I wonder if the new one has a larger bore. I can easily make a small orifice fitting to restrict flow. I think the ID was ~ 4mm, so I will reduce it to ~2mm.

But there is no pipe from the top of the turbo, just the drain / feed pipe to the lower rear.

I will also try removing the calorifier take off to vent that.
Click to expand...

Flow through exhaust manifold is critical.

Bed time reading Cummins B-Series Coolant Plumbing
 
superheat6k said:
Following several weeks with plain fresh water in my cooling system following the engine repair to make sure the engone was leak tight, this morning I added the antifreeze. I also have successfully repaired the broken spout on the expansion bottle.

But I am having trouble getting the air out - as the engine warms it is pushing considerable volumes of the coolant into the expansion tank, which it thens sucks back soon after shut down as it cools. I'm not losing coolant so I know it isn't going into the exhaust manifold and the spill over isn't severe enough to suggest exhaust is coming the other way (there is a hidden joint on the exhaust manifold to turbo charger connection).

So I suspect this is simply trapped air pockets which will considerably expand with temperature, whereas the liquid expansion is minimal.

So any tips for getting the trapped air to move into the header tank. There are a couple of vent valves but these are simply producing coolant flow without bubbles.

Thanks.
Click to expand...
It seems you have a significant volume of air in there.
Can you work out where the air is likely to be?
What are the high points in the circuit which will not naturally pass the air to the pressure cap?
Sometimes you can crack a join somewhere high in the circuit and squeeze the lowest hose to lose the air.
Sometimes you can mostly fill the system 'from the top'.

Be afraid, if you have a big air bubble which finds its way to the cylinder head, it will do damage!

Once the bubble is small enough to be carried along by the water flow, it will sort itself out.

Are you getting flow through the cylinder head? Is the hose out of the head convincingly warm?
Soemtimes it will all sort itself out when the thermostat opens, but you need to be sure the heat is getting from the head to the thermostat.
 
I was shagging around and found a meter of clear hose would jam into where removed the pressure cap, about 40-50mm hose. So filled with water, ran motor,a big burp, water everwhere, and think she got rid of the air.
 
It does, but today I resolved the school boy error of not tightening the pressure cap on the expansion bottle !

I attached two lengths of clear tube to the high point vents and used the soft return pipe from the cooler to agitate the coolant, which resulted in about at least a litre of air being removed (measured by the extra I had to top up with).

Anyway the expansion tank is now sitting more or less level, and no more air is rising from the vent tube.
 
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