Subaru Outback Forums banner

1 - 20 of 41 Posts

·
Registered
2006 Outback LLBean Edition
Joined
·
9 Posts
Discussion Starter #1
Hi All,

2006 Outback LL Bean with 125K, and I am a bit overdue for my 120k service.

Please forgive the wall of text that is about to occur...

A few weeks ago I was driving from Pittsburgh to Central PA (lots of mountains on this drive). It was the first hot and muggy stretch of weather we had so I was running the AC kinda hard. About halfway through the drive I noticed the temp gauge was rising pretty high (not red-lining). Stop at a gas station and they had no coolant, so I wait it out. 45 minutes later the temp gauge is below operating temp, so I figure I would be good to go since I'm only about 40miles from my destination (I know, not the best decision).

As soon as I began driving, the temp immediately starts to climb but drops back down to operating temps on the highway. It does spike while climbing hills, but goes back down on the descent. Eventually get to my hotel and figure I'll deal with it in the morning. There ended up being a leak in the driver side upper radiator hose. I was able to replace the hose, fill the car with coolant, and drive home without incident.

Current Issue
Over the past week I have been having an issue with the temp rising while I'm idling for too long while running the AC (stuck in traffic, slow drive-thru lane, etc). I cut the AC, turn on the heat, and after about a minute it will drop back to operating temp. It got particularly bad yesterday and I ended up topping off the coolant in the radiator this morning, but before I topping off, I noticed that the overflow tank was completely full. After topping off today, the issue occurred but it was less frequent.

Other info...
- Changed the oil about 1000 miles ago and it is still looking pretty good.
- The radiator does seem to be holding pressure
- Used a block tester and the liquid stayed blue (yay?)

The block tester gives me hope that it might not be a head gasket issue, but I'm not ruling it out completely. I'm hoping to get the car in to the shop early next week, but was wondering what others might think the issue might be?

Thanks!
 

·
Registered
2005 Legacy GT wagon 5MT Limited
Joined
·
320 Posts
If I understand correctly, you're saying the cooling system is not pulling coolant from the reservoir. In that case, I would
- check the reservoir hose and pipes
- burp the air out, with a no-spill funnel if necessary
- replace the radiator cap (OEM only!)
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
Discontinue AC use until you get this one solved. Running hot invites trouble, particularly with head gaskets.

Meaning: you may have a really simple fan, hose or radiator issue now but continued overheats are going to turn that into a failed head gasket quickly.

Overheated motor oil doesn't count as motor oil anymore.
 

·
Registered
2006 Outback LLBean Edition
Joined
·
9 Posts
Discussion Starter #4
Thanks everyone!

One thing I forgot to mention is that all the fans appear to be working. However when it begins to overheat, it sounds like there is another fan kicking on? Unfortunately I'm always driving it when it occurs so I can never pop the hood and take a look.

I'm, of course, going to be mentioning the issue to my mechanic when I bring it in for my 120K. In the meantime I'll try burping again (and probably picking up a no-spill funnel for it) and switching out the reservoir hose. The cap seems fine, but I may as well switch it out too. I'll be cutting the AC use as well.

One person at the auto parts store said that it might possibly be a thermostat issue as well. Could there be any truth to that?
 

·
Registered
03 H6 OBW & 06 WRX Sportwagon
Joined
·
17,711 Posts
If you decide to also replace the thermostat, avoid some typical aftermarket - it must be OEM or perhaps the OEM-style made by Stant.

after losing or draining coolant, it can be tricky removing all the air from Subaru cooling systems. One trick is to cycle to operating temp and then allow to cool for hours with the nose of the caar elevated. Perhaps do that twice if possible. You must maintain a level of coolant in the overflow tank so coolant can be pulled back in.

Until you're confident the issue is resolved, be vigilant about the temp gauge and check coolant in the radiator, don't trust the level in the o'flow tank to reflect the system's actual coolant volume.

On my cars, I put a couple of small zip-ties to act as a clamp on the small hose going to the o'flow tank. Put them on at the rad's neck to ensure an air tight connection.

Some folks have reported intermittent fan operation. Also, clean any dead bug carcasses/debris from in between the condenser and radiator.
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
You can try slicing the end of the recovery hose to prevent it from vacuuming itself to the recovery tank floor.

My 2006 Outback is on its second radiator now- the seam split on the top tank, a common failure point on these. It tends to create a slow leak, but because the system can't hold pressure it loses a lot of cooling efficiency. Look for a green salt crust near the seam. You may need to move the foam air gasket to see it.

The vehicle has two fans. Over the years the logic for these fans has been altered, so I'm not 100% certain which ones should be running at which times, though I do know that when AC is active both should be operating.

These fans can fail electrically, running under-speed, intermittently failing to start altogether, or completely failing.

You can verify basic fan operation by putting the car in relay test mode with the green connectors under the dash, then go up front and make sure they cycle on and off.

The heater core can clog up- you'd notice more heat on the left side vents than the right. When this happens, the thermostat can be "starved" of hot water, causing it to close and leading to overheat.

The radiator can clog up- either bugs and leaves on the outside, or mineral salt on the inside. When either happens you lose a lot of efficiency, and these are hard to clean vs. ~$100 for a new aftermarket radiator. Outback cooling systems have very little reserve capacity, so any efficiency loss shows up prominently.
 

·
Registered
'06 Outback 3.0R, '91 Justy, '93 Loyale, '15 Crosstrek, '04STi (RIP)
Joined
·
25 Posts
I have the exact same issue with my 2006 3.0R base model.
I just got the car this winter with 200k km on it and the issue just started to appear with the summer temperatures. The temperature runs normal if it is below 25*C outside with the AC on. Anything above that and the coolant temp rises to about 2/3rds on the gauge. Turn the AC off and it goes back to normal.
I couldn't find any signs of leaks in the coolant system so I ordered a new radiator from Rockauto and am waiting to find the time to install it.
I'll report back if it solves the problem.
 

·
Registered
06 Outback 2.5i, 06 BMW 325xi wagon, 02 2.5rs, 82 CB750, Polaris XC SP 500, and a single speed bike.
Joined
·
869 Posts
Radiator is clogged. Here's the thought behind it (and spoken from experience on my 03 after moving to south Texas for six months in the middle of summer):


The A/C condenser is in front of the radiator. When the A/C isn't running, the air in the condenser is the same temperature as ambient. When you turn the A/C on, you're introducing hot air into the condenser which raises the temperature of the air flowing through the radiator. Typically, this isn't a problem but if you have restricted flow through the radiator the system isn't able to deal with the added heat and the coolant can't cool down enough before returning to the motor, hence... running hot and eventually overheating.


I would check for debris between the condenser and the radiator, and if there's a bunch clean it out. If there's just some crap down at the bottom don't worry about it -- that's not your root problem. If you clean the debris out and it continues to run hot with the A/C on you'll need to replace your radiator.
 
  • Like
Reactions: je513412

·
Registered
2009 Subaru Outback 3.0R Limited
Joined
·
104 Posts
Just to add to this, I have an 09 3.0R and just took a trip where I drove about 2500 miles and there were a lot of mountain passes. I noticed on just about every mountain pass that the temp gauge would creep up. It only ticked up about 1.5-2 notches on the gauge, but it was a big enough change to make me nervous. I know these cars are sensitive to this. I also know that cooling is one of the bigger limitations of these cars because of their design, but I just figure it should be able to climb a 6% grade for a bit without the temperature ticking up too much. I was running the A/C on these climbs until I saw the gauge start ticking up and then I would shut it off and it wouldn't climb anymore, but didn't return to normal very quickly. As soon as I got to the downhill side it would drop right back to normal. I was down in Mexico and I had a similar issue as the OP where I was idling at the border waiting to have our passports checked and I saw the temp gauge creeping up slightly, so again I turned off the A/C and it settled back down. It never overheated, per the gauge. It never got closer than about 3 ticks down from 3/4.

I mean, it's a 10 year old car, so I assume a new radiator would help immensely, like @CSFiend said, right? Or should I be worried about bigger issues?
 

·
Registered
2008 Outback 2.5
Joined
·
959 Posts
Try this:
When at a stop light, if you see the temperature rise, put the car in neutral and gently give it a bit of throttle. If the temperature goes down, the system is cooling due to higher RPM and higher pump speeds similar to driving at highway speeds. You may have either insufficient coolant in your system or as the others are saying, insufficient cooling from the radiator due to clogs, debris on the outside or something else.

Check the coolant level under the radiator cap each morning for a few days. It should be right at the very top.

You could try to burp the system by getting a Lisle spill free funnel (about $30). You attach it to the filler neck of the radiator, put some coolant in the funnel and run the engine until it gets to operating temperature and the thermostat opens. You might get a constant tiny stream of bubbles coming up through the funnel. That's OK. A big burp once is OK. Constant big bubbles out of radiator is not good (likely a blown head gasket or boiling within the engine cooing passages).

PS Reading your OP again, if you are noticing that the radiator level keeps going down and you are topping it off without removing any coolant from the reservoir, and after several top-offs your reservoir is completely full, it means that coolant is getting pushed out of the radiator and not getting completely sucked back into the engine when it cools off.

Theoretically, even with a little air in the cooling system, when the coolant expands, it will eventually blow the air out the pressure cap and when the engine cools, it will suck coolant back in from the reservoir. Over several cycles, you should end up with no air in the cooling system and the liquid at the very top of the radiator neck.

When I open the radiator cap on my OBW, I see that the coolant is at the very top of the neck with no air pocket at all below the pressure piston.
 

·
Registered
'06 Outback 3.0R, '91 Justy, '93 Loyale, '15 Crosstrek, '04STi (RIP)
Joined
·
25 Posts
Swapped out the rad this evening before a week of 30*C temperatures. The outside of the old one was pretty plugged up, a cleaning might have fixed it but for the price of a new one I'd rather not do the swap twice. I'll add pictures tomorrow once I'm at a computer.
 

·
Registered
'06 Outback 3.0R, '91 Justy, '93 Loyale, '15 Crosstrek, '04STi (RIP)
Joined
·
25 Posts
Well it was +28*C yesterday on my 65km commute home and the temperature gauge was rock solid in the middle with the AC on the whole way so it looks like the new radiator fixed my problem.
Hopefully it's the same easy fix for the OP!
 

·
Registered
Joined
·
18,299 Posts
Well it was +28*C yesterday on my 65km commute home and the temperature gauge was rock solid in the middle with the AC on the whole way so it looks like the new radiator fixed my problem.
Hopefully it's the same easy fix for the OP!
Been following.

That's great.

Understand the outside of the rad was blocked (still can't view the photos). But it also has me wondering if there was clogging of the radiator tubes.

What are you doing with the old one? If it's just a hunk of metal for recycling, any interest in removing the end tanks and having a closer look at the tubes? I ask because there's been at least two, if not more, cases here recently of blockage in the cabin heater core -- jelly-like material filling much of an end tank, restricting flow and probably also blocking the tube.
 

·
Registered
'06 Outback 3.0R, '91 Justy, '93 Loyale, '15 Crosstrek, '04STi (RIP)
Joined
·
25 Posts
Yes, it was the outside that was blocked.
I was just going to recycle the old one.
How hard is it to remove the endtanks?
 

·
Registered
Joined
·
18,299 Posts
Yes, it was the outside that was blocked.
I was just going to recycle the old one.
How hard is it to remove the endtanks?
If your's is the same as the one on my 07, I believe the top and bottom tanks (they're actually half tanks) are held to the core by a band all around with "tabs". I'd probably just cut off the band to remove it, and I think the top and bottom pieces should come off (maybe with a bit of help -- there might be some original sealant, or a rubber seal that both parts are sticking to.)

Nothing to lose if it's headed to metal recycling in any event.
 

·
Registered
2008 Outback 2.5
Joined
·
959 Posts
I couldn't get a good close up of the old radiator. Is the blockage due to debris or are the thin aluminum fins bent?

If it's clogged with debris, couldn't you simply spray water from a garden hose in the reverse direction to unblock the radiator? I do that once in a while with my cars. Lots of bugs, leaves and other junk come right off and I have a clear air path again.
 

·
Registered
2006 Outback LLBean Edition
Joined
·
9 Posts
Discussion Starter #18
Wanted to give an update...

Replaced the Rad Cap and the issue still persisted a bit, even after buying a no spill funnel and trying to burp the system.

Finally had the 120k service performed at my local shop over the weekend (though it was a few thousand miles late). They did say that there was air in the system which was causing the overheating and that they bled it out.

Drove it a bit yesterday (Monday), but drove it quite substantially today. It is in the 90's and muggy, so I have been running the AC. Sure enough the problem began again. I popped the hood just to make sure there weren't any leaks or anything and it looks like they put in Red coolant instead of the Green that the car had previously had.

Is this something that I should take back and have changed immediately?
 

·
Registered
03 H6 OBW & 06 WRX Sportwagon
Joined
·
17,711 Posts
I think you'd do just as well to continue with the investigation - the shop probably used a perfectly fine coolant like Zerex asian red or similar.

wouldn't hurt to call them with your concern.
 

·
Registered
2006 OutBean, 2005 LGTW
Joined
·
1,443 Posts
I'm having a similar problem with our h6 outback as well.

We bought the car knowing it overheated (3/4 mark on the gauge) going uphill on a hot day with the AC on. The previous owner, prior to selling us the car had the radiator replaced, but the issue persisted.

After I bought the car, I pulled the thermostat and tested it. Seemed to work okay so I stuffed it back in. I also water hammered the heater core which yielded nothing. Water flowed through it just fine and the heater works great. (Personally, I don't believe the heater core can clog enough to prevent flow though it as Subaru seems to have included a built in bypass that even if the heater core area was clogged, the bypass would allow coolant to simply flow around it.) Winter set in though, and the car showed no signs of issues so I haven't been able to replicate the "fault." With the onset of summer, however, the overheating has returned. This finally opened up the opportunity to diagnose the issue. On a hot day (~100f) I drove it up the steepest hill we have around here. She pushed out a portion of her coolant and the ECT gauge made it to the 3/4 mark. I pressure tested the cooling system and it held pressure overnight. Even though the previous owner had the radiator replaced, the mechanics used the original radiator cap and when I compared it to a new one, it was obvious it was worn. Slapped the new radiator cap on (OEM of course) and took it up the hill again on another 100 degree day. This solved the engine pushing coolant out through the reservoir but did not solve the overheating (3/4 mark on the gauge) condition. Correlation, but not causation.

Perusing the FSM (CO(H6DO)-7), I noted the fan diagnostics/inspections were pretty specific in regards to voltage to the fans from the fan control unit. I have a Legacy 2.5GT as well so when I plugged in the test leads under the dash on my LGT and compared the test leads being plugged in on the H6 Outback, I was amazed at the difference in sound made by the fans. The LGT fans come absolutely unglued compared to the H6. Aha I thought. Going through the diagnostic tree in the FSM--the last step is to test the "waveform" or voltage output of the RFCU (radiator fan control unit) with the test mode connectors plugged in. The FSM specifically states if the voltage waveform output goes from 5v to 0v, replace the RFCU. I don't have an oscilloscope but the leads coming out of the original RFCU were exposed so I just put my volt meter on it. Unfortunately, my digital voltmeter wasn't really fast enough to get the drop off to get an accurate read but it seemed to me that the fan was turning on and then turning off and the voltmeter read ~5v and seemed to drop off to lower than 2v before the computer kicked the voltage back up to 5v. This sort of made sense as I compared it to my LGT which seemed to alternate between high and low fan speeds--the H6 was low speed and off. The FSM indicated the waveform I was seeing was faulty and the RFCU needed to be replaced.

I hate throwing parts at cars. I like faults to be definitive. In my head, the fan not kicking up to high speed made sense to why the car would overheat. On a hot day, with AC running, going up a steep hill--the fan not kicking up to high speed is what's preventing the engine from cooling down. I took a chance and ordered the $250 RFCU which unfortunately is coupled with the fan and unavailable separately. A week later, I had it installed in the car. Plugging the test mode connectors back in under the dash, I got a definitive alternation of voltage from 5v to 2.5v and back. I thought the computer would kick from 5v to 12v like the LGT but it seems the H6 has 3 speeds the fans run at, depending on conditions, and the LGT may only have two. Regardless, the next trip up the hill resulted in the same overheating condition. I was able to confirm however that the fan does in fact run at a higher speed--something I had never heard it do before. Didn't fix the issue though.

Yesterday, I decided to tear into it. I swapped out the old thermostat for a new one since I had it on the shelf. I blew compressed air through the oil cooler lines and the line leading up to the heater core--neither of which seemed blocked. I inspected several of the lines while I was there and nothing seems to be faulty. I used an inspection mirror to see the back side of the water pump which seemed to be intact. I did not attempt to try to physically turn the back side of the water pump to see if it was a solid connection to the gear on the front but I intend to do that today when I tear the car back apart. The engine was still hot AF lol.

What else could be left? If the water pump has lost efficiency or is cavitating, that could explain the overheating issue as it's just not moving water through the system fast enough. Is there any way to test the flow of the water pump? The pump does have 203k miles on it after all. I've found no instance in which any of the records I got with the car indicated it had been changed. I was a bit peeved to see when the previous owner had the timing chain tensioners changed when the motor jumped time they opted not to include a water pump. It's a cheap part comparatively.. just do it while you're there, you know?

I'm inclined to want to trust the temperature sensor but I suppose it could be faulty or off a bit.
I don't trust the efficiency of the water pump. Subaru gives a specification of 84.5 gallons per minute at 5500 rpms. How could I even test that?
Thermostat, radiator and cap are all new. Since I didn't swap out the radiator personally I suppose it could still be a problem but it looks new inside (from what I can see) and out. The AC condenser is not clogged and the fans seem to be able to draw air through both it and the radiator without a problem.
Heater core is not clogged and flows freely. Heater temperature (as measured by the dash vent) is within a couple of degrees of ECT. The heater also has the ability to pull the ECT down when in use.
Hoses seem clear and unobstructed as does the oil cooler unit.
I don't suspect head gasket as there's no bubbles or other tail-tell signs.
The cooling system has been properly bled and best I can tell there's no air pockets left to purge out.

I'm truly stumped...
 
1 - 20 of 41 Posts
Top