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Hey all, sorry for the bump! I just replaced my radiator with a Koyo Rad, and changed my timing belt, water pump, thermostat, etc.

I am about to fill the radiator with coolant. In this video:

How To Change A Subaru DOHC EJ20 EJ25 Timing Belt - YouTube

He fills the coolant from the filler tank, and opens the radiator cap on top of the radiator as he's pouring. You can see some huge air bubbles come out. Will this help the whole process of burping? Also, if you fill coolant from the filler tank, does the coolant reach into as many parts as it can without the car circulating the coolant, meaning if I fill from the filler tank, does the radiator itself get filled, along with all the other components minus the plastic reservoir/over flow bottle?

This is a great thread and been very helpful!

Last question, if I use to spill free funnel to burp, I can leave that on the filler tank while I do the warm up/cool down process? Will it bleed the whole system or will I need to do the same thing for the radiator cap on top of the radiator?
Yes, so that upper coolant resevoir is the best place to fill. What I did when I did my rad flush... was that I prefilled the radiator, placed the cap back on for a tight seal. Then I put poured coolant in the upper resevoir. The upper res is the highest point in the cooling system, so as air pockets try to escape, they have no where else to travel but up. If you have that yellow cooling funnel it helps modestly because it will overflow.

The car has to run through fan cycles and that lets you know that the thermostant had probably already opened so you'll notice the coolant level getting sucked in--- away from the yellow funnel, don't ever let that run dry or you'll risk air pockets. As that happens, it starts to burp... blast the heater to make sure that you have coolant running through the core, should only take about 15-20 some odd minutes. Then in the morning, you can check your plastic overflow and fill it accordingly. Best done on a flat surface obviously.

If your heater is not blowing warm air yet, you have not cleared some air out of the system. Especially if it's intermittent cool/hot air... hope that helps... anyone else care to chime in would be great!

EDIT/ADD - By the way, morning after and through the week is essential to check your plastic overflow, I have a line that runs from the radiator to the plastic overflow on my 04STI, and sometimes I see it bubble/burp on like the 2nd or 3rd day, which is fine, then the next morning that plastic overflow level has gone down a moderate amount. If you notice that the plastic overflow looks fuller when the engine is warm, that is normal because of the pressure. 20,000 miles later, no overheating or leaks.
 

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I realize this thread is a bit old but I’m hoping someone will see this! I just have a question about the filling process.

So, after draining the coolant from the radiator (with the filler tank cap and radiator cap off), I screwed the pet cock back onto the radiator and began pouring my fresh coolant mix into the FIlLER tank and nowhere else. I was only able to get just over a gallon into the filler tank before it reached the neck and wouldn’t go down anymore.

My question is: should I also fill up the radiator before I start my car? Or will the radiator fill itself once my car is running, and I add the remaining coolant to the filler tank?

thanks a lot for the write up and everyone else’s contributions. I’m just a little stumped as it’s my first time and I’m not sure whether to fill the radiator or not. Some people have said they filled their radiator but that they filled the radiator first and then the filler tank. I’ve already put a gallon or so into my filler tank.
 

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Always fill the radiator and the Top filler ends up into the radiator so your fine, burp the car of bubbles whichever method your familiar with. I use the coolant funnel kit to purge the air.


Sent from my iPhone using Tapatalk
 

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Always fill the radiator and the Top filler ends up into the radiator so your fine, burp the car of bubbles whichever method your familiar with. I use the coolant funnel kit to purge the air.


Sent from my iPhone using Tapatalk
Since I’ve already poured a gallon into the top filler, is it too late for me to fill up the radiator as well?

Thanks for the help, I’ll look into the funnel kit too
 

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You should fill the radiator to the top as well as the top filler as they're the same system. Give your overflow some as well (to the cold line) and it's always best to use the kit linked above unless you like spilling fluid all over your engine bay. If you keep your overflow bottle filled appropriately, the system will add/remove what it needs once all the air is bled.
 

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You should fill the radiator to the top as well as the top filler as they're the same system. Give your overflow some as well (to the cold line) and it's always best to use the kit linked above unless you like spilling fluid all over your engine bay. If you keep your overflow bottle filled appropriately, the system will add/remove what it needs once all the air is bled.
Appreciate the answer, thanks!
 
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