Working on a 02 legacy gt. my coolant will not flow from the tank back into the radiator when it cools. I'm confident it's not the head gasket they are fairly new and I have also replaced the radiator cap still no fix. Any ideas on what to try next? Can overflow tanks go bad and cause for a loss of vacuum at the cap? Or if the hose connecting the two aren't completely a snug fit could that cause my issue. The car runs fine other than not draining so I have to empty it out manually after a long drive and top the system off. Any one else ever run into this problem? Any ideas? Could a radiator going bad cause this issue? I just flushed my system out and that didn't help but water didn't flow through it great, seemed like it could have run through a bit better. Thanks guys and gals!

As long as the hose from the radiator to the overflow tank is not full of holes, one end is securely attached to the radiator nipple, and the other end is in coolant in the tank it is "vacuum tight" (ie. would normally draw coolant back in). The overflow tank itself is not air tight, and doesn't need to be.

 

Could you clarify why you mean by: "The car runs fine other than not draining so I have to empty it out manually after a long drive and top the system off."

 

I'm a bit confused. Is the overflow tank filled with coolant between the markings? I usually check when it's hot - upper line.

Edited July 31, 201312 yr by nickb21

It's running fine as far as the coolant temp staying steady. No residue in the antifreeze and no smoke out the exhaust. Thanks

When I refilled the system I filled the radiator and filled the tank to to cold mark, ran the engine for a bit and then pushes the air out and topped it of again. When it's cold now it is at the hot full mark

make sure the hose going into the over flow bottle is not pressed against the bottom of the bottle.

in other words, pull the hose up, out, of the bottle about 1/2 inch.

see if that makes a difference.

 

other things that will cause your problem have been mentioned.

but maybe a bad cap could hold pressure in one direction but not in another.

 

or possibly a low pressure leak somewhere that seals at high pressure.

this sound really lame, but who knows?

One post I read, a replacement radiator needed to have the nipple that the o'flow hose fits on drilled out!
 
confirm that nipple isn't clogged or cracked, that the hose isn't split or have a hole, that the radiator cap is good, etc.

 

Do you ever see the upper or lower rad hose collapse?

Most people feel a Subaru cap is best. Certainly, the cooling system's thermosat MUST be OEM or OEM style.

 

Edited July 31, 201312 yr by 1 Lucky Texan

Even with a small leak the system should still pull most of the coolant back in when it cools.

 

The hose going into the overflow must reach to about 1/2" from the bottom of the bottle, if its cracked or cut just a few inches into the bottle it can't suck up any coolant below that point.

Thanks you guys, I'm going to replace the hose and see if that works and make sure it's not hitting the bottom. I had a bad thermostat that was sticking open and shut while driving so I replaced that but it was an aftermarket from napa. Fixed the issue that caused but I was hoping it would help this one also. This is one of those pain in the rump roast things that you can throw part after part at it to figure out what's causing it. Then at the end you find out its a 2 dollar easy fix.

If you just had the system open you could just have too little coolant in the system. A large amount of air stuck in the system will prevent the coolant in the reservoir from being pulled back in.

Open the radiator cap and let the engine run up to normal operating temp. Top off coolant level in the radiator as necessary. Be sure to open the bleeder valve on the opposite side of the radiator if it has it.

i am not the most experienced so i do not know everything .

but, i have NEVER seen a subaru T-stat go bad.

 

i have heard of them being replaced as a preventative,

and i have heard of them being replaced for overheating,

and i have heard of issues related to after market replacements,

 

but usually in a situation like yours,

the t-stat is blamed for a problem caused by something else.

it gets replaced with an after market item and still the problem.

a subaru unit is installed, and still the problem.

 

i hope the subaru t-stat fixes it.

 

be sure to add the ''coolant conditioner''.

$2.50 from subaru.

this is very important.

i would add 2 bottles.

Edited August 1, 201312 yr by johnceggleston