Subaru Outback Forums banner
1 - 20 of 75 Posts

·
Registered
Joined
·
86 Posts
Discussion Starter · #1 ·
Hello,

Long time reader, first time posting. I have a 2006 Outback 3.0R with 100k on the clock, which overheats after only a short stint going up steep grades. To be clear it approaches the 3/4 line, I have never let it go beyond that. I live in AZ so it is pretty much 80+ most days. I have been chasing this issue for a while as I do a lot of driving and my stress level increases every time I see a hill regardless if I am loaded or not. I have changed all radiator hoses, new Subaru thermostat, new radiator and flushed with Subaru super blue coolant + the additive. I also purchased one of the special no leak funnels to ensure I burped the system completely of air.

Although I have never pushed it into the red this does not seem normal. Immediately after the grade, the temp comes back to normal operating temp. It does seem to be doing this on less and less steep hills. I have done just about everything I can think of except the dreaded HG because I was hoping to avoid that by buying a 3.0. I know a few people have had this issue wondering if anyone could give some insight or next steps. Oh, and I have never seen bubbles in my overflow even when it is hot.
 

·
Registered
1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
Joined
·
1,224 Posts
Try replacing the rad cap with a new OEM one from Subaru. Only other thing is maybe the water pump? Not an easy task to replace IMO
 

·
On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
·
27,163 Posts
subaru oem rad cap. ? even on a aftermarket rad that comes with a cap, there is no sub for a OEM rad cap as it mesures in KPA and not PSI like the aftermarkets.

also

on EZ30 it is important to burp and burp again. park the car facing up grade, let it cool fully open the rad cap and put a funnel on the rad neck that locks / screws to it. (rad up grade,...so the funnel is higher then the heater core).

start engine and turn on the heater.

the rad fluid will rise in the funnel as the car heats and any air will burp out. run for half a hour.

turn the car off and wait for the fluid to drain down. remove funnel. replace cap. and hopefully live happily ever after.

sometimes you got to burp x2 with these. or you find after a pressure test you got porus lines. or a bad heater core. and you will be happy with those vs. head gaskets and a JDM used 250hp EZ30 engine. (the quick easy and cheap fix to head gaskets on a H6).
 

·
Registered
Joined
·
86 Posts
Discussion Starter · #6 ·
Thanks Eagleeye, I will try your burping method tomorrow. The rad cap is Subaru OEM. One thought, if my heater core was bad wouldn't it not produce hot air? it blows super hot and seems to be functioning.

Also instead of parking on a hill can I just lift the front end?
 

·
On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
·
27,163 Posts
Thanks Eagleeye, I will try your burping method tomorrow. The rad cap is Subaru OEM. One thought, if my heater core was bad wouldn't it not produce hot air? it blows super hot and seems to be functioning.

Also instead of parking on a hill can I just lift the front end?

good you are getting hot air. a sign any air bubble is not at the heater core. (one or more maybe still poking around causing trouble elsewhere).

and yeah just lift the front end,...ramps, jacks, curb. liitle grade on a driveway.

make sure your hoses are not sucking themselves closed when you are watching.
 

·
Registered
2005 OBXT Limited, VF37, STI intake, 5MT
Joined
·
1,610 Posts
start engine and turn on the heater.
I always have to chuckle at this, Subaru's don't have a heater core flow control valve (they haven't since the old EA71 chassis). This is old, blanket advice from the 70's. The heater core is a constant-flow design, the water flows thought it even if you have the AC on. Turning on the heater just makes your interior hot.

The tell-tale for bad head gaskets in the EZ30 (like the EJ-series) is look for bubbling in the overflow bottle. Bring the RPMs up to 2K and hold for 30 secs or so. Goose it a few times and check the bottle for any signs of bubbling. "Gushing" or moving water (when hot) is not necessarily bad, but bubbling/boiling is.

When it starts to get hot, if you let it idle, does the temperature start to come back down? Does the temperature climb into the red VERY quickly?

If it's slow to heat and cool, I'd look at a clogged radiator. Long intervals between fluid changes or using non-distilled water (tap, spring, and bottled are NOT acceptable replacements for distilled!), this can lead to a sediment and element-clogged radiator.

These EZ are pretty robust, so if you're experiencing overheating issues, it's usually head gaskets or a poor radiator.
 

·
Registered
2008 Outback XT 5EAT
Joined
·
14 Posts
Jungr,
I think it's worth bypassing the heater core to make sure it's not the issue - it only take about 10 minutes to do. All you need are a couple of 5/8" ID connectors, hose clamps and a piece of hose (I used the gates 18777 to avoid any kink in the bend).

I had been chasing a very similar "overheating" issue for a couple of months on my XT. Turns out my heater core was blocked just enough to prevent efficient coolant flow so the temp rises very quickly when under load; yet flowing enough to still provide plenty of heat out of the vents. Just had the core replaced on Friday, and all seems to be well.
 

·
Registered
Joined
·
86 Posts
Discussion Starter · #10 ·
Thanks for the reply! To answer your questions when it starts to get hot I can let it idle and the temp will never increase always slowly go back to normal operating temp. When I flushed the system I used filtered water (guessing maybe this is not the same as distilled water) when I was bleeding the system and would rev it up to about 3k for 5-10 seconds I would see foam like small bubbles getting pushed back up in the no-leak funnel. Is this the bubbles you are talking about? I have never seen that in the overflow certainly never been boiling or overflowed the overflow ha.

I will also try the heater core bypass thanks for the suggestions!
 

·
Registered
2008 Outback XT 5EAT
Joined
·
14 Posts
yup, I just covered the core inlet/outlet to keep crud out doing the test drive and looped the two hoses that went to the core.

I did try back flushing the core by repeatedly filling it with distilled water and blowing it out with with compressed air, which helped a little but did not restore full cooling efficiency (bottom is inlet, top is outlet, BTW). I'm currently running coolant without the "conditioner", as I'm questioning whether that contributed to the clogging.

The hose is only like $10 at the store, but since I have no use for it anymore, I'd be happy to try to throw it in the mail for you if you want to wait a few days.

All the symptoms you've mention were exactly what I was experiencing, so hopefully this solves you're issue as well.
 

·
Registered
Joined
·
86 Posts
Discussion Starter · #16 ·
@BioDoc Thank you so much for your wisdom. I was able to order one off Amazon for $7 with free shipping. Probably cheaper than what shipping would be. I will try this out and hopefully, all I need is a new heater core. I will report back after this test. Thank you for taking the time to respond.
 

·
Registered
Joined
·
19,508 Posts
yup, I just covered the core inlet/outlet to keep crud out doing the test drive and looped the two hoses that went to the core.

I did try back flushing the core by repeatedly filling it with distilled water and blowing it out with with compressed air, which helped a little but did not restore full cooling efficiency (bottom is inlet, top is outlet, BTW). I'm currently running coolant without the "conditioner", as I'm questioning whether that contributed to the clogging.

The hose is only like $10 at the store, but since I have no use for it anymore, I'd be happy to try to throw it in the mail for you if you want to wait a few days.

All the symptoms you've mention were exactly what I was experiencing, so hopefully this solves you're issue as well.
Appreciate very much this contribution. The importance of the heater core flow for proper thermostat operation has long been suspected, but your example, and perhaps @jungr 's, if it comes to that, would provide the objective evidence.

When the old core was removed, was it examined to find the cause of restriction? If not, do you still have it and would you be willing to have a look and report back? Perhaps @traildogck ?
 

·
Registered
2008 Outback XT 5EAT
Joined
·
14 Posts
The importance of the heater core flow for proper thermostat operation has long been suspected, but your example, and perhaps @jungr 's, if it comes to that, would provide the objective evidence.
?
]yeah, it was the over-cooling (to ~170, below the thermostat crack-open temperature of 176) on long downhill stretches (i.e. off throttle/no load, at speed) that first suggested a restricted heater core.[/COLOR]

I did ask for the old core back so I can dissect it to see if I can figure out what happened.[/COLOR]
It looks absolutely pristine on the outside. Trying to come up with a systematic approach of opening it up to get as much useful info as possible.
[/COLOR]
Open to suggestions...[/COLOR]
 

·
Registered
1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
Joined
·
1,224 Posts
I was thinking about the heater core myself today. Glad to see that others share their knowledge!
 
1 - 20 of 75 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top