25 replies to this topic

[Dylan]

Hi guys, I've had the misfortune of getting a blocked / leaking heater core in my Suby. Heater worked great, bloody great infact - but the inside of the cabin heats up and cools down and various intervals, and the BIGGEST giveaway that this is leaking / blocked is that my passenger side footwell (carpets) are WET! I've done some research and removed the heater core from the coolant system (by putting a loop hose from the coolant outlet on the engine, back to the inlet). I will get some photos of this when I put on a correctly fitted hose (one currently is a bit kinked - will reduce flow). Now, what I am after is some advice: Is this flow of coolant crucial to the cooling system on a Subaru engine or not? I.e. if the outlet and inlet on the engine are completely blocked off will coolant still flow correctly or will I risk overheating? The reason I am asking this is, will the kinked hose cause major dramas or will it be OK (Providing it does not burst)? I am trying to find a coolant diagram for the WRX engines as we speak, if I have any luck I will share with all - but if my above concerns could be addressed that would be great. Thanks, Dylan

[XXB4XX]

To be honest Dyl you did what I would have told you to do, but will suck in winter mornings.. Coolant flow actually increases when you do this as most v8 owners will tell you, as the waterpump doesn't have to push the water through the heater cores.. If anything a kink will be a positive!

[Evil_VZ-T]

connect the Two lines on the engine block, This will divert the coolant and still keep it to be able to flow around the engine like normal. without having a restriction there.. If coolant pools up and doesnt flow in some area's the temprature of the coolant will increase drematically and possible cause overheating.. (think Ford 6 cylinder heads, when the coolant and the rear pools up, due to lack of coolant flow in the area = headgasket blown. All Head Services reconditioned Heads fix this with their bypass hose mod) Best way to cool and engine down is to turn on the heater normally.. as it gives the coolant more surface to travel along and lose its heat

[Dylan]

Nice! Yeah, I only plan on leaving the heater core out of the loop for another month or two MAX, Alex suggested I try get my hands on one from a wrecker and get that one reco'd so that I can just take my dash out, and swap the cores over in quick succession.

Taking the dash out is a MASSIVE PITA.

I only did it a couple of months ago to replace a relay as well

connect the Two lines on the engine block, This will divert the coolant and still keep it to be able to flow around the engine like normal.

Best way to cool and engine down is to turn on the heater normally.. as it gives the coolant more surface to travel along and lose its heat

Well I'll be damned ! Thanks mate.

Proving quite hard trying to find a diagram of where the coolant flows on these ej's though.

[RX25SE]

Mmmmm.... Depends if the system is designed with a heater tap to turn off the heater or a flap to send air around the heater core. If it uses a tap (from memory Subies do'nt) then a kink is not a problem. I would bypass the heater in a kinkless manner, given that Subaru cooling systems tend to be a little, shall we say, fragile. Is it dash out to replace? I hate doing heater cores!!!

[Evil_VZ-T]

i got a diagram at work in one of the Suby Manuels, will try and scan it tomorrow if i get time. but take Alex's advice and recon a 2nd handy... do the job once = WIN

[Dylan]

Mmmmm....
Depends if the system is designed with a heater tap to turn off the heater or a flap to send air around the heater core.
If it uses a tap (from memory Subies do'nt) then a kink is not a problem.
I would bypass the heater in a kinkless manner, given that Subaru cooling systems tend to be a little, shall we say, fragile.

Is it dash out to replace?

I hate doing heater cores!!!

Yep. After having a chat to a mate tonight though, it seems the Suby may be a tiny weeny bit EASIER to do than a VS (I think is that model). The heater core in his mrs car is blocked, and he said you've got to take the radio and pedal assembly out to be able to get a new core in there, or remove the dash that's not entirely meant to come out. Interesting.

Jason, I feel uneasy about having a kink in the hose too - unfortunately I need the Suby tomorrow and I've got to be somewhere in the morning - so don't have any time before hand to fit a new hose unfortunately.

The bloody water pump is leaking on the Astra as well - just after the alternator has been replaced. Grr. CARS!

i got a diagram at work in one of the Suby Manuels, will try and scan it tomorrow if i get time.

but take Alex's advice and recon a 2nd handy... do the job once = WIN

Cheers mate, if you can grab that info that'd be awesome.

Off the top of my head it won't be in my Haynes manual - although I have to find that and then have a squiz.

[CodeBurn3r]

im pretty sure its not a good to block those coolant pipes off. when i was at subabits if we were to test an engine out of a car the boss was always sure to use a special hose that had a u in it for the pipes. one time i just got a piece and it was kinked because of the way it is and he was not happy, i think needs to flow through there, use a loop sure but dont block it off or limit it at all.

[Aaron.W]

dylan i should have a heater core lying around here somewere if i find it ill give u a buzz

[RX25SE]

Yep. After having a chat to a mate tonight though, it seems the Suby may be a tiny weeny bit EASIER to do than a VS (I think is that model).

Cool.

A VS takes about 20mins so you should do it in 15.

[CRUISN]

Mine did this on my 2.2 a few months after i bought it. In winter. 5am morning surfs in 8 deg with no heater after. That sucked.

[Soop]

Stab it. Then spit on it. Then call it nasty names.... Works for me.

[Xon]

Cool.

A VS takes about 20mins so you should do it in 15.

Haha not unless you're an asian midget with an electric ratchet. Dash out is a PITA of a job!
Dylan I still don't think that a bit of a kink will cause a huge amount of problem, there's plenty of pressure in there. As long as it's not split, and the hose is held on firmly...
Mind you... keep the mobile charged just in case?

[Alex]

Make sure you don't kink the lines.

This is imperatively crucial.

Subarus rely on the fact that there's always water flowing through the heater core.

Block it off, and you'll have cooling dramas. Guaranteed.

Borrowed off RSLC. (thanks mitcho)

So your cars been over-heating, We'll after discussion with Xeon hes come up with a fix.

Sam, (xeon) concluded that it was his heater core that was blocked, as was mine. So he bypassed the heater core with a 180* bit of hose. And blocked off the heater hoses that come out of the firewall to prevent coolant from pissing everywhere.

This is the commodore spec heater bypass hose



Then you chop it



This is what its like when stock and heater will work



And this is after the little Bypass mod



I did this today and now my temps are brilliant at about 76* to 84*.

Hoe this helps some people as it helped me and sam with the headfu(k of overheating all the time.

[RX25SE]

100% Alex Rep point coming your way.

[Dylan]

Cheers Alex. Going to try and get my hands on one of those hoses tomorrow I think. Aaron - thanks mate let me know. I've got a V4 STi core here, not sure if it's the same though ??

[alexGT]

i doubt they will be the same. impreza has a different dash and all.. if it were a blocked core you could try and undo both hoses and flush it out with a garden hose. btw you won't believe it i chucked a gen2 heater core out a month or so ago....

[RX25SE]

if it were a blocked core you could try and undo both hoses and flush it out with a garden hose.

I have done this with varying degrees of success.
What usually happens is they leak not long after.
The crud is preventing it from leaking.
Best to keep the coolant in perfect condition (flush and replace every 1.5-2 years) to prevent that rusty cruddy buildup.


If you are pulling the dash, fit a new/reco heater core.

[Alex]

Alexxx. Dylan has stated that he has wet carpet.

Flushing the core is clearly a dumb idea in this instance...

As discussed, it's simple.

1) Bypass with hose as posted above.
2) Source new/reconditioned/second hand core. If s/h, get it reconditioned.
3) Swapsies.

[alexGT]

i doubt they will be the same. impreza has a different dash and all..

if it were a blocked core you could try and undo both hoses and flush it out with a garden hose.

btw you won't believe it i chucked a gen2 heater core out a month or so ago....

Alexxx. Dylan has stated that he has wet carpet.

Flushing the core is clearly a dumb idea in this instance...

hence the IF