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00/4 Forester S, X Auto, Auto
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318 Posts
Discussion Starter · #1 ·
Hey guys,

My wife's 04 blew the radiator on Christmas Eve, luckily no damage because it happened as she pulled in our driveway. Finally got it to the shop, new radiator, upper and lower hoses and OE thermostat & Zerex Asian Coolant. The lower hose will not warm up, it starts to get hot after a long warm up period. Pulled the t-stat and checked it in hot water and it opened. Reinstalled and same issue. What are the chances of an air pocket on a boxer engine? What have you done to get this working again?

She's missing her baby and I'm missing mine since she's driving it. LOL

HELP!!!
 

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1989 Turbo II 5spd TII
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62 Posts
Correct me if Im wrong but I believe the water travels into the engine from the lower radiator hose and exits from upper. Since the ambient temperature is cold (winter) your cooling system is at its best.

Sitting still warming up will eventually get the lower radiator hose hot but the fans take care of that (at idle) at any other point, its the air from actual driving that cools the water/antifreeze in the radiator.

As far as bubbles in the system, air pockets in the cooling will actually make you run hotter or over heat.

Hope that helps.
 

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00/4 Forester S, X Auto, Auto
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Discussion Starter · #3 ·
It does thanks! After about 15 minutes or so it does overheat. The lower hose remains cold while the temp climbs. I'm gonna err that there are air pockets. Shame they don't make a machine to force fluid around faster do burp it better than a water pump. Wonder why they didn't put air bleeders on em?
 

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1989 Turbo II 5spd TII
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After you refill and burp the system, start it up with the heater on full heat, full blast. This will allow coolant to run through the heater core. Let it cool off and check fluid once more.

I believe there is a bleeder but a pain to get to. The bleeder is on the aluminum housing on the upper radiator hose.
 

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00/4 Forester S, X Auto, Auto
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318 Posts
Discussion Starter · #5 ·
Turns out to be the weirdest thing. I've been in the parts business for almost 30 years and have never seen this.

The impeller shaft snapped in half. No damage to the rest of the engine. With the water pump dead water flow stopped. Pressure built up with the rising temp. Radiator went poof!

Got a new pump on, gonna start it back up in the AM and see what happens.
 

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2019 Crosstrek 2018 Forester XT
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14,921 Posts
Fill the system..drive it a few miles...let it cool. Then add more coolant directly to the radiator.. You may need to do this 3 times. I kinow its a PIA but it is guaranteed to work.

Water flows through the heater core all the time (as far as I know) so turning the heat up does nothing unless they changed the design.
 

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00/4 Forester S, X Auto, Auto
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318 Posts
Discussion Starter · #7 ·
Got everything buttoned up. Let her idle for almost an hour nice and normal temp. Took her out of the interstate to "blow" it out and same result. Nice and normal temp.

Again I look at the impeller shaft on the pump and it still perplexes me. Impeller missing off the pump yet no damage to the timing parts nor the engine.

Guess I'll chalk this up to major lucky!
 

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1998 Forester S 4EAT
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574 Posts
It does thanks! After about 15 minutes or so it does overheat. The lower hose remains cold while the temp climbs. I'm gonna err that there are air pockets. Shame they don't make a machine to force fluid around faster do burp it better than a water pump. Wonder why they didn't put air bleeders on em?
They do. Snap On has a cooling system vacuum tool. It will suck all of the air out of the system and hold a vacuum. To relieve the vacuum, they have a bypass hose that you submerge in your new coolant.

Viola! You are purged :cool:
I used this tool at school all the time, they work great.

That is so weird! I've never heard of that happening!
 

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00/4 Forester S, X Auto, Auto
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Discussion Starter · #11 ·
Looked too clean to be cast. I'd say stamped but not sure. It was an Aisin pump with about 20,000 on the clock. Threw it out cause it had Chief Rain Cloud written all over it. Didn't want that kinda karma hanging around the garage!
 
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