'06 Outback LL Bean H6 runs hot at higher speeds

[jonjonbear]

Hello all,

New guy here. I've been hanging out at the Outback forums since buying this car so this post will be redundant for the guys over there.

We bought this car in Houston, TX. Drove 175 miles from our town to buy it. When we drove it around Houston everything was fine. Very hot day, and the temp gauge was dead center.  We buy the car and get on the road coming home.  After a while (driving about 80mph, and it was about 103 degrees that day) the gauge began to rise. It went as high as about 1/8" below the top of the white "normal" scale. When we changed highways to a lower speed road, the temp then dropped down to just above center.  It can idle all day long, or drive around town and the gauge stays dead center.  I then put my Ultragauge in the car to monitor the actual temps. 

What we have done so far:

Changed the thermostat-factory stat, and in the correct position

Flushed the cooling system and added new coolant. Took the overflow bottle out and washed it out. Had a Tiny bit of sediment in it but not bad.

Changed the plugs, changed the oil (Mobil One 5w30 w/factory filter.

Additives: Royal Purple purple ice in the cooling system and Liquimoly Cera Tec friction reducer in the oil.

Used the fancy funnel and made sure all the air came out. Was quite difficult but got it done with the front wheels up on ramps. No bubbles in the radiator.

Seems there are a few H6 Outback owners who have cars doing this, and nobody has found a solution. One guy has changed everything including his radiator and cooling fan computer. Here is what my temps are doing:

In the morning, it's about 75 degrees. The car quickly warms up to about 195 and stays there for about ten miles. If I climb a hill, the temp goes up a bit. If I stop at a light, the temp remains the same until I accelerate, then it goes up to about 203. After it goes up that high, it usually won't go back down below 200.  In the afternoon when it is hot out 90+ degrees, it will go as high as 218 degrees and the gauge just starts to go up.  When the temps were in the low 100s, it would sometimes go up to about 225. As soon as you take your foot off the gas, coasting to a traffic light, the temp goes down.

One suggestion I made, given this was my first Subaru, that maybe this was normal? I came into this car from a Toyota Camry that you could probably drive into the sun and the temp gauge would never move.  I have no idea what "normal range" is for this car but any time a temp gauge goes up that far, it worries me. Plus the car is so hot you can't put your hand on the hood. The guy with the same car who has done everything said the guy he bought the car from, bought it new and sold it to him because nobody could fix it, so that rules out "normal" I guess. I have not changed the radiator, but when we cleaned it I looked inside and the tubes were squeaky clean. Looking down between the condenser and radiator, the radiator looks clean and the fans operate as they should. 

So I have spent weeks searching the internet and found a site from NZ, where this guy found that a blocked or partially blocked heater core could cause this. What he did, he put a cross over between the heater hoses hoses. Basically a tee in both hoses with a piece of heater hose between (see attached photo). This insures good flow, and also still allows the heater to work...A couple of the guys did it and it fixed their problem too. This process I've not seen done anywhere else so wanted to see if anybody here might have any ideas, or think that perhaps I should try the heater hose bypass?  Seems almost as if someone would make a heavy duty radiator for this car, that would fix it but maybe it is a bypass flow problem.  It's never boiled over, never lost coolant or have not had to add any, but yesterday I did notice a small bit of coolant smell from the grill area. Looked over everything and didn't find any wet spots or leaks, and system is still full and the overflow tank level is normal (I also cut the hose at an angle).   Sorry this is long, but I know there are a lot of questions that would be asked that are probably answered here.

Cheers,  John in Bastrop, TX

Edited September 19, 2018 by jonjonbear

[GeneralDisorder]

Change the radiator. If that doesn't help try that bypass trick. If it still does it, then you need new HG's. Sorry. 

GD

[jonjonbear]

Thanks GD for your reply. Question, and you seem to be the professional so I respect your opinion. From what I have read, if I had head gaskets leaking, I would have bubbles in the coolant, the coolant would be pushed out of the radiator into the reservoir, and I would have to add. Is this not the case? I've never had to add any coolant and after the initial "burp" we had zero bubbles in the funnel.  That said, is their any difinitive test? I take it that it's best to replace the engine, than to replace the HG, correct?  Car only has 123K on it and runs perfect. I just bought this car because my last car blew it's engine. Would just be my luck to have another bad engine, and this one I have to pay for for three years!

Thanks for the help,

 

John

[GeneralDisorder]

Chances are the HG's are ok. But the radiator is over 10 years old so replace it regardless. Also check for any obstructions in the condenser fins and between the condenser and radiator. Get new hoses FROM THE DEALER. They fit the best and aren't that expensive. 

GD

[jonjonbear]

Oh one thing to add. When we got home tonight I used the laser thermometer and hit  the two heater hoses where they enter the firewall. They were 10+ degrees different.

[jonjonbear]

1 minute ago, GeneralDisorder said:

Chances are the HG's are ok. But the radiator is over 10 years old so replace it regardless. Also check for any obstructions in the condenser fins and between the condenser and radiator. Get new hoses FROM THE DEALER. They fit the best and aren't that expensive. 

GD

Would a high quality after market rad be okay, say like a Denso? I see the one from the dealer is like 300.00.

[GeneralDisorder]

Yeah Denso or Koyo is fine for the radiator. Just get the hoses from Subaru. 

[jonjonbear]

On 9/19/2018 at 8:35 PM, GeneralDisorder said:

Yeah Denso or Koyo is fine for the radiator. Just get the hoses from Subaru. 

Morning GD, well we did the bypass since we had the stuff to do it. While in there I pulled the upper radiator braces and pushed the radiator back against the engine and sure enough, along the bottom, especially on the pass side of the radiator is dirty. Almost looks oily, then dirt got in it. Buttoned it back up and ordered a Denso radiator and will put in this next weekend. Not sure if the bypass did anything or not. The weather cooled off but it will go up to about 204 when I accelerate from a traffic light but then calms back down to about 198.  74 degrees out. When we have the radiator out, I'm going to pressure wash the condenser from the back side (hose pressure nozzle, not high pressure) to make sure it's clean too.

Hoping that new radiator will help!  

[GeneralDisorder]

204 is normal - that's where the fans come on. Though when driving it shouldn't need the fans so if the system is working efficiently it will stay usually below the fan set point if you have good airflow across the radiator. 

[idosubaru]

Radiator - clean/inspect the fins/make sure nothing is blocking them, and run a hose through the radiator to see if it's restrictive.  It should flow full volume of average SFH hose bib.

HG.  Initial EZ HG's can be variable in presentation - it probably isn't HG but your symptom description by no means precludes them. 

The heater core bypass is questionable - other explanations are more plausible, or they're outliers.  wasn't burped right, hose or clamp that was problematic was repaired during the fix or the issue returned later but the poster never posted back years later when the symptoms persisted or got worse.  I've seen H6's take over 2 years to go from initial overheat to confirmed HG failure - that "I think it's fixed" thing is very common on those and EJ25D's.  seen it tons of times and it lends itself to poor follow through on internet forums. 

[jonjonbear]

3 minutes ago, idosubaru said:

Radiator - clean/inspect the fins/make sure nothing is blocking them, and run a hose through the radiator to see if it's restrictive.  It should flow full volume of average SFH hose bib.

HG.  Initial EZ HG's can be variable in presentation - it probably isn't HG but your symptom description by no means precludes them. 

 

I have to say I was a bit happy to see the crap in the bottom of the radiator fins. So hopefully this will help putting the brand new radiator in. Being original it won't hurt anyways to have a new one. As for the head gaskets, with the engine putting pressure into the cooling system, that would cause coolant to be forced out and into the recovery tank, correct?  First, i've never seen the car "boil over". the coolant in the recovery tank level varies between the two marks depending on if the car is hot or cold. Other  than when we lost coolant by removing a hose, we've never added coolant. That would be a good sign that the HG would be okay, correct?  The car seems to hold pressure well, and then draw coolant back in when it cools off.

When we burped the system, that was quite a challenge. We ended up putting the car up on ramps and put the fancy funnel on the radiator and it took quite a while to get the coolant running through the system. The temp would go up, the fans would turn on, then they would start speeding up, then the temp would go down, over and over. At one point it felt like I could feel bubbling in the lower hose, but it wasn't hot. I then shut it off for a few minutes, and then started over. Revved it up to about 3K for a couple of minutes and a bunch of bubbles burst out of the funnel. Seemed like racing the engine did the trick. The lower hose then was hot, the temp went down to 194 and the fans turned off. The bubbles slowly diminished and after about 10-15 minutes, had stopped so we buttoned it back up. Now we're going to have to do this all over again when we put the new radiator in, but at least now I know what to expect. It'll also give me the opportunity to make sure the AC condenser is clean. Maybe it's not really overheating. I'm just not used to a car who's temperature gauge moves from center. Does anyone know what the "normal' temp range is? I don't even know where to look that up. In the couple of months that we've had the car, in the hottest months in Central Texas at 100+, I don't think it's ever gone over 222-225 and that's when the gauge starts to climb. I think it's only gotten that hot once or twice.  On the factory gauge, it's never gone past that little hashmark between center and the top of the white line. (3/4 mark?) Pushing it hard will run the temp up pretty fast it seems. Just taking off from a traffic light with moderate/heavy acceleration brings it to about 205, then it goes back down once the speed levels out.

[idosubaru]

Sounds like the radiator will do it. 

You don't appear to have random overheating so that's good.  But yes - they can fail without consuming coolant in the initial stages for over a year before finally progressing to more symptoms. The few I've seen just have sporadic, random overheating - usually during times of high demand - high ambient temps, A/C on, etc....even to the point they'd had no overheating events for 6 months (all winter) then start back up again small, minor, random overheating events over the summer with no coolant loss over long periods of time.  

 

[jonjonbear]

On 9/24/2018 at 2:32 PM, idosubaru said:

Sounds like the radiator will do it. 

You don't appear to have random overheating so that's good.  But yes - they can fail without consuming coolant in the initial stages for over a year before finally progressing to more symptoms. The few I've seen just have sporadic, random overheating - usually during times of high demand - high ambient temps, A/C on, etc....even to the point they'd had no overheating events for 6 months (all winter) then start back up again small, minor, random overheating events over the summer with no coolant loss over long periods of time.  

 

So far so good! We pulled the old radiator out on Sunday. Was a lot dirtier than I thought.  Also power washed the front of the engine and the engine bay in front of the engine and plastic cover, and also the condensor. Put it all back and purged it and took it for a run. It ran noticeably cooler. This morning coming in which is a 25 mile trip, It only went over 200 a couple of times but the fans would turn on, and it would go back down to 188-194 ish. Definitely seems like it helps a lot. Will see going home this afternoon when it's warmer.  

[idosubaru]

good job!  load dependent running hot is often radiator.  i've seen them overheat during daytime driving but not nighttime for instance, or only when going up hills.