The simple solution

[tcspeer]

The simple solution and why it works. I know many people here have trouble getting the coolant full and taking air traps out of their Subaru's, they have been many people post about how to solve this problem and most work well. But why remove heater hoses or radiator hoses or loosen vent caps what ever they are. All that needs to be done is remove radiator cap, start the engine when it is cold and turn heater on. The open cap will let the air out just as well as removing hoses. As the coolant circulates you can add more each time it is sucked down. This has worked many times on my Subaru's and I have had two different ones.

[nipper]

The simple solution and why it works. I know many people here have trouble getting the coolant full and taking air traps out of their Subaru's, they have been many people post about how to solve this problem and most work well. But why remove heater hoses or radiator hoses or loosen vent caps what ever they are. All that needs to be done is remove radiator cap, start the engine when it is cold and turn heater on. The open cap will let the air out just as well as removing hoses. As the coolant circulates you can add more each time it is sucked down. This has worked many times on my Subaru's and I have had two different ones.

 

Thats I was taught to do it by my father (whos knowledge dates back to shooting at Fuji equipment), in highschool shop, and in engineeering school.

 

nipper

[svxpert]

that might work when you need to replace a small amount of coolant but that method won't work when some people mistakenly take out the radiator when doing a timing belt job.

when there is no coolant in the engine block, you must fill through the engine block first, then fill the radiator. i have posted on this many times before.

 

 

 

The simple solution and why it works. I know many people here have trouble getting the coolant full and taking air traps out of their Subaru's, they have been many people post about how to solve this problem and most work well. But why remove heater hoses or radiator hoses or loosen vent caps what ever they are. All that needs to be done is remove radiator cap, start the engine when it is cold and turn heater on. The open cap will let the air out just as well as removing hoses. As the coolant circulates you can add more each time it is sucked down. This has worked many times on my Subaru's and I have had two different ones.

[tcspeer]

It has always worked for me, even when taking the radiator out. Which I always do when going into the front of the engine. If you prefer to remove your hoses and fill yours that way then that's fine. I was just offering an easily way then some have been doing it. Please explain how you get more coolant into block by taking hose loose rather then letting it run into the block from the hose that is connected to the radiator.

that might work when you need to replace a small amount of coolant but that method won't work when some people mistakenly take out the radiator when doing a timing belt job.

when there is no coolant in the engine block, you must fill through the engine block first, then fill the radiator. i have posted on this many times before.

[avk]

To me the most important thing seems to fill it up slowly. Some air does get trapped but it purges out eventually. What reaches the radiator and gets pushed out through the overflow hose, can't go back in. Takes a cup or two of coolant mix to finally correct the level. More on a minivan with a second heater core in the rear. Try to purge that.

[Setright]

Well, as my long winded explanation - abundant on these pages - states in bold, leaving the cap off and waiting for the fan to switch on is the sure-fire way to be certain that the thermostat has opended and airbubbles pumped out.

 

Removing the upper rad hose, to fill an empty engine isn't strictly necessary, as you say tcspeer. However, it does make for far less air trapped inside the block, and for some us that gives peace of mind when warming up an engine. It means that more coolant is present inside the engine block, and that means a more even distribution of cooling effect.

 

Filling via the rad neck means that coolant must seep through that tiny hole with a plug in it on the thermostat. Effectively, the radiator fills quite quickly and once near the brim, coolant spills over through the top rad hose and that's when the slow rising flow from the thermostat housing is "confronted" with the flow from above. That means a large air pocket inside the block. Sure, it will be purged if you leave the cap off and heat the engine fully, but it seems a less elegant method to me.

 

Filling via the top hose is a smidgen more complicated, but worth it for sticklers like me

[86BRATMAN]

First gen legacy radiators have a plastic screw type fitting on the passengers side top of the radiators that were put there for air bleeding such as this. At least all the non turbo's I've seen have had it.

[tcspeer]

Growing up with the old ford and chev's from the past with the thermostat near the top of the engine has spoiled me, I have never had trouble filling any car I have owned with coolant until I came across Subura. I think the reason is because the thermostat is near the bottom of engine, but I dont know that for a fact. I think we all find our ways of getting this job done, I just dont like the ideal of removing hoses to put coolant in.

Well, as my long winded explanation - abundant on these pages - states in bold, leaving the cap off and waiting for the fan to switch on is the sure-fire way to be certain that the thermostat has opended and airbubbles pumped out.

 

Removing the upper rad hose, to fill an empty engine isn't strictly necessary, as you say tcspeer. However, it does make for far less air trapped inside the block, and for some us that gives peace of mind when warming up an engine. It means that more coolant is present inside the engine block, and that means a more even distribution of cooling effect.

 

Filling via the rad neck means that coolant must seep through that tiny hole with a plug in it on the thermostat. Effectively, the radiator fills quite quickly and once near the brim, coolant spills over through the top rad hose and that's when the slow rising flow from the thermostat housing is "confronted" with the flow from above. That means a large air pocket inside the block. Sure, it will be purged if you leave the cap off and heat the engine fully, but it seems a less elegant method to me.

 

Filling via the top hose is a smidgen more complicated, but worth it for sticklers like me

[tcspeer]

After rereading your post that is a very good explaination of why the air trap happens, and it is easy to see why your way also would work well, I just never figured out why the trap was happening. I was sure it had something to do with the thermostat on the bottom but did not relate it to the little seep holes.

Well, as my long winded explanation - abundant on these pages - states in bold, leaving the cap off and waiting for the fan to switch on is the sure-fire way to be certain that the thermostat has opended and airbubbles pumped out.

 

Removing the upper rad hose, to fill an empty engine isn't strictly necessary, as you say tcspeer. However, it does make for far less air trapped inside the block, and for some us that gives peace of mind when warming up an engine. It means that more coolant is present inside the engine block, and that means a more even distribution of cooling effect.

 

Filling via the rad neck means that coolant must seep through that tiny hole with a plug in it on the thermostat. Effectively, the radiator fills quite quickly and once near the brim, coolant spills over through the top rad hose and that's when the slow rising flow from the thermostat housing is "confronted" with the flow from above. That means a large air pocket inside the block. Sure, it will be purged if you leave the cap off and heat the engine fully, but it seems a less elegant method to me.

 

Filling via the top hose is a smidgen more complicated, but worth it for sticklers like me

[porcupine73]

How's about refilling the cooling system under vacuum? It's mentioned in an EndWrench article and it seems like a neat idea, i.e. if there's little air in the cooling system it can't really get trapped. Mityvac and others sell kits to do this, but of course they're $$. I've assembled but not yet tested a poor man's version using harbor freight and mcmaster.com components.

[tcspeer]

I have not seen this, maybe for a shop this might be worthwhile, being time is money and the ways most of us have found to get the job done is time consuming. I think you need to try the one you have assembled and if it works you could share the ideal with the rest of us.

How's about refilling the cooling system under vacuum? It's mentioned in an EndWrench article and it seems like a neat idea, i.e. if there's little air in the cooling system it can't really get trapped. Mityvac and others sell kits to do this, but of course they're $$. I've assembled but not yet tested a poor man's version using harbor freight and mcmaster.com components.