Vacuum tool to fill cooling system

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I have a vacuum tool that can fill the cooling system and eliminate air pockets. What is the procedure if the cooling system is full but you suspect air pockets? (Did not use the vacuum tool). Drain most of the coolant and refill using the vacuum tool?
 
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The procedure is to drive the vehicle. Don't exactly know what vehicle your referencing, but most modern cooling systems operate in a similar manner. This section is from one of my Mopar FSMs:

COOLING SYSTEM DE-AERATION

Air can only be removed from the system by gathering under the pressure cap. On the next heat up it will be pushed past the pressure cap into the coolant recovery bottle by thermal expansion of the coolant. It then escapes to the atmosphere in the coolant recovery bottle and is replaced with coolant on cool down. To effectively deaerate the system, multiple thermal cycles of the system may be required.

NOTE: De-aeration does not occur at engine idle, higher engine speeds are required. Normal driving will deaerate cooling system.
 
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I have a vacuum tool that can fill the cooling system and eliminate air pockets. What is the procedure if the cooling system is full but you suspect air pockets? (Did not use the vacuum tool). Drain most of the coolant and refill using the vacuum tool?

You can vacuum as long as you don't pull coolant out. The vacuum makes the air pockets bigger and allows them to escape. Driving and heating does the same, but won't work if the pockets are totally stopping flow.
 

Donald

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Basically if there is a fully filled area of coolant between the tool and the air pockets then the tool will suck coolant. So need to drain enough coolant so that is not the case.
 
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Basically if there is a fully filled area of coolant between the tool and the air pockets then the tool will suck coolant. So need to drain enough coolant so that is not the case.
Vacuum fillers only work with a mostly empty system. Your best option is to drain the coolant into a clean container and use the vacuum filler to fill it back into the system.
 
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Vacuum fillers only work with a mostly empty system. Your best option is to drain the coolant into a clean container and use the vacuum filler to fill it back into the system.
I agree with this. It's also very satisfying to refill with the vacuum tool.
I assume you suspect an air pocket because of intermittent overheating or warnings, but there is also a chance there is something else wrong.
 
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My worry always is that an air pocket will allow local overheating... especially of the cylinder head... and the ensuing potential damage. In past I've used a big funnel and I've (fully-) taped a circular piece of sheet metal into the bottom, with said piece having a small hole in it. Coolant then goes-in at a very slow rate. Also, jiggle valve (on T-stat) has to be at 12o'clock...
 
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I agree with this. It's also very satisfying to refill with the vacuum tool.
I assume you suspect an air pocket because of intermittent overheating or warnings, but there is also a chance there is something else wrong.
Also, always pressure test a cooling system after vacuum filling. Vacuum filling will not find all leaks.
 

Donald

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My worry always is that an air pocket will allow local overheating... especially of the cylinder head... and the ensuing potential damage. In past I've used a big funnel and I've (fully-) taped a circular piece of sheet metal into the bottom, with said piece having a small hole in it. Coolant then goes-in at a very slow rate. Also, jiggle valve (on T-stat) has to be at 12o'clock...
In my case it's a boat engine and the engine is not overheating but the water cooled exhausts are. I have other posts in the boating forum. The exhaust manifold riser up so they are higher than the top of the cylinder head. Attached is a picture and you can see black exhaust manifolds at top and bottom of the picture. (V8).
 

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I've used pretty much all the aforementioned approaches. My fav is the drop and refill because it's thorough.

I have a combined pressure test / vacuum fill kit.

Putting the system under maximum pressure will shrink the bubbles significantly so even at idle they'll often make their way to the expansion tank.

Slowly pulling a vacuum will expand the bubbles so they'll push their way out of wherever they're stuck, then when you drop the pressure back the remaining bits having been shrunk will often make their way back to the tank. Do pay attention using this method because not paying attention and allowing the coolant to burp up into the vacuum rig sees it exit the venturi at speed and makes a huge mess. I'd like to say I learned from it, but then I did it again.

On my current ride there's a quick disconnect at the bottom of the fuel cooler and I can get > 9 of the 11L out from there, faster under pressure. Pulling it back in under vacuum makes for a thorough fill.
 
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