Hi everyone.  Two weeks ago I purchased a rust free 1985 Subaru DL.  When I picked up the car, the heat worked great but after driving it home (200 miles) I began to hear really odd noises coming from the heater core and my heat when the car was warmed up was dismal.  It sounds like water is going to explode out of the heater core onto the floor boards, however there is no leaks.  Coolant level remains steady.  This week I found that the radiator cap was old and quite loose so of course I put a new one on.  I burped the system and a bunch of air came out.  The heat is now working much better than it did BUT I still hear crazy water rushing and air noises from the heater core area.  It is almost as if there is air in the heater core.  When I go around a turn and/or rev up the motor and the water pump gets thing flowing the rushing water noise in the heater core sounds incredibly bad.  Sometimes I have to look down at my feet to make sure nothing is exploding on to my feet.

 

My question is even though I bled/burped the system, could a lot of air still be trapped in the heater core?  If so, why in the heater core?  Is my heater core on its way out or is there a way to get all of the air out?? I do know the car sat in a barn for over 2 years without ever being started.  Would a complete flush of the system and refill help things?  I'm really weirded out about this.  Please help!!! 

It sounds like air in the system, try jacking up the front end turn the heater on full blast and reburp the system

It sounds like air in the system, try jacking up the front end turn the heater on full blast and reburp the system

 

i will try that!  However I am about to do timing belt water pump and oil pump seals in a few weeks.  I may just wait to do a total flush since I have to drain the fluid anyways.  Any other reason for so much air in the system?  Radiator cap is now sealed.

These cars are notoriously hard to get all the air out of, as long as the coolant level doesn't go down I'd say its probably fine.

If you get a hose for a washing machine, and cut it in half, you can flush the system right at the heater with full water pressure and full catchment. Then flush the core in both directions for a good cleaning . You can leave the system all together by pinching off the supply to the motor before you pull the hoses at the firewall. The washing machine hose should fit right on unless its some fancy braided one or something weird.

Thanks everyone!  I will try this today.

These cars are notoriously hard to get all the air out of, as long as the coolant level doesn't go down I'd say its probably fine.

 

What is the reason these cars are notorious for holding on to trapped air?  I thought my '98 GTI VR6 was finicky with coolant and air bubbles, but this car takes the cake.  I've never heard a heater core make the noises that this DL does.  My girlfriend swears water is going to come out on her feet.  

 

What is the reason these cars are notorious for holding on to trapped air? I thought my '98 GTI VR6 was finicky with coolant and air bubbles, but this car takes the cake. I've never heard a heater core make the noises that this DL does. My girlfriend swears water is going to come out on her feet.

I don't know why there so hard to burp out, I think its because of the desighn of the cooling system, esecialy the height of the heat core compared to the rad cap. That's why you need to get the front end up

IMHO any restriction in the heater core (example, it is 20% plugged up with crap) makes it almost impossible to bleed the air out. Any amount of flushing these things in the car at reasonable pressures usually leads to a come-back due to noise. Replacing the heater core, while not always the most attractive solution, is uually what is required to eliminate 100% of the gurgling noise inside your dash board and restore proper toasty winter heat output. 

 

This assumes that the impeller on the back of your water pump is attached and spinning and that the thermostat is working, radiator not restricted also, etc.

Edited November 25, 201411 yr by Crazyeights

Heater cores on these aren't too difficult, the hard part was finding the right core!  Oreillýs, Baxter, Carquest, and Autozone all have incorrect part # listed.  I used Murray # 94792, one of the tubes was incorrect.  I had the radiator shop sweat the old tube from my old core off and install it in place of the wrong tube on the new core.  Cost me a total of $115.00 in parts / service.  Aside from all of that, I agree with raising the front end.  Has been the only way to get it done right on the last few Legacys and Imprezas  I've done.

Edited November 25, 201411 yr by Beladona_13

IMHO any restriction in the heater core (example, it is 20% plugged up with crap) makes it almost impossible to bleed the air out. Any amount of flushing these things in the car at reasonable pressures usually leads to a come-back due to noise. Replacing the heater core, while not always the most attractive solution, is uually what is required to eliminate 100% of the gurgling noise inside your dash board and restore proper toasty winter heat output. 

 

This assumes that the impeller on the back of your water pump is attached and spinning and that the thermostat is working, radiator not restricted also, etc.

 

Replacing the heater core sounds very unattractive.  Does the entire dash have to be removed or is there a trick to get her out without doing all that?

Replacing the heater core sounds very unattractive. Does the entire dash have to be removed or is there a trick to get her out without doing all that?

There is a trick to pulling the core without pulling the dash, some searching and you'll find it.

I believe they use a soldering iron to cut the box around the core

There is a trick to pulling the core without pulling the dash, some searching and you'll find it.

I believe they use a soldering iron to cut the box around the core

 

No way............you'd never get the pipes out of the firewall.

 

There is no way to pull the heater core without removeing the dash.  Pulling the dash is not that hard. A few bolts, Lots of connectors, 2 cables, one vac line.

 

Before pulling dash......remove both heater hoses and use a garden hose to flush out the core both directions.....they get clogged, restricted flow, causes the weird cavitation and accompanying sounds.

No way............you'd never get the pipes out of the firewall.

 

There is no way to pull the heater core without removeing the dash. Pulling the dash is not that hard. A few bolts, Lots of connectors, 2 cables, one vac line.

 

Before pulling dash......remove both heater hoses and use a garden hose to flush out the core both directions.....they get clogged, restricted flow, causes the weird cavitation and accompanying sounds.

I have seen on this forum a way to pull the core without pulling the dash. I don't remember the details though

Well I went out this afternoon and jacked the front up nice and high.  Low and behold lots of air bubbles came out!  THe heater is making a lot less gurgling noises and blowing nice toasty air!

 

Watch the bubbles:

 

http://www.youtube.com/watch?v=4TJXVdzvniw

I have seen on this forum a way to pull the core without pulling the dash. I don't remember the details though

 

Perhaps on an EA81 car were you can remove the hoses from the core near the valve.....inside the cab.

 

EA82 cars the brass tubes run a few inches through the wall.....so unless you can pull the HVAC unit away from the wall there is no way to get the core out.