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Discussion Starter #1
I logged my coolant temps on a drive home on an 80F degree day - they were stable at 195F - 200. One brief uphill pass (foot on the floor, flat out) and the temp spiked to 222 - and took quite a while to shed that excess.

My fans are operating; I'm assuming the radiator is sized for a normally-aspirated engine and less adequate for the turbo XT.

To help the cooling I've replaced the factory oil cooler with a sandwich take-off plate and standalone cooler mounted on the top of the bumper - so the radiator doesn't even have to deal with that extra load.

I looked at the schematic for the radiator fans and since they're ECU -driven and extra complex (2 bits instead of 1 !) - I'm considering the possibility of an ECU bug - My temps run up with the A/C on but not when off and it looks like there's quite a decision matrix when the A/C gets involved. This smells, in part, like a software issue to me.

[ I can see the priority given to keeping the A/C from swinging wildly instead of cycling both fans full-on and half-speed ...]

Otherwise, my fans seem to be working.

So. I'm considering a bigger radiator, a 3'rd fan in front of the A/C condenser, a simple coolant temp switch to run both fans flat out when the temps exceed 200F or so, water wetter ...

The water wetter goes in tomorrow, can't hurt.

Thoughts on what's worked for people? and thanks for reading this far,

-M.
 

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2005 Outback VDC limited 3.0r
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Sounds more like the radiator could be plugging up externally from dirt/bugs. The radiator is plenty fine in stock and lightly modified XTs. Also considering that with more load on the engine(AC) it creeps as well, could hint to the radiator. Whats your coolant level at both in the rad and reservoir? Any recent coolant work done? Could be an air pocket as well.
 

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Discussion Starter #3
I had the engine out recently to replace the turbo; new coolant, no obstructions that I can see.

And the temp creep precedes this work - maybe I'm being picky, but there just doesn't seem to be enough capacity/head-room for more than one burst of boost without quite a bit of cool off time. I'm just not happy with 220 degree coolant temps in the summer.

I could try a new radiator, this one is original to the car - 14+ years old.
 

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Outback 2011 3.6R Premium
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220 Is not a problem for these motors and they are much happier running hotter than colder.

I think you are overthinking it ;-)

Seagrass
 

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Discussion Starter #5
220 Is not a problem for these motors and they are much happier running hotter than colder.

I think you are overthinking it ;-)

Seagrass
Yah, I do that sometimes. What are the benefits of running 220 over, say, 200?
Thanks for the thoughts.
 

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Yah, I do that sometimes. What are the benefits of running 220 over, say, 200?
Thanks for the thoughts.
@cardoc is probably better able to explain this but it has to do with the efficient burning of fuel and therefore overall engine efficiency and performance.

220 Farenheit is just over the boiling point of unpressurised water and with coolant and pressure the boiling point is much higher. 15 PSI of pressure raises the boiling point to around 255 without coolant and around 270 with 50/50 coolant.

Seagrass
 

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Discussion Starter #7
Ok, I get that; my concern is for the apparent lack of head-room or capacity in the system. It's the water version of the argument for a larger oil sump.

That and the fan turn on/off temps in the service manual are in the 93 - 96 degree C range (iirc, I don't have that pdf in front of me) - lower than the temps being observed with the AC on, even without throwing hard driving at it.

As far as the overthinking goes, it's an occupational hazard as I'm a retired firmware engineer ... Take that with my view of Subaru's history of engineering curiosities, complexities and bad ideas and I'm left second-guessing the system design.

If I felt strongly enough about it I'd log the 2 fan control lines from the ecu ... I'd almost bet with the AC on only the secondary fan signal is activated - which switches both fans on - wired in series, each running at half speed.

... That without an apparent ECU over-ride when the coolant temp spikes. Turning the AC off brings the temps back down.

it would be easier just to add a stand-alone coolant temp switch to pull a relay to tie both fans to ground, running them at full speed.

thanks again,
Mark
 

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2001 VDC/SC One of a Kind
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@traildogck can also chime in.

As long as the temp doesn't run up to 235 your safe. The increase when you're under higher boost is due to a few factors. First is the increased combustion temperature. This is brought about by the higher intake air temperature created by pressurized air and the fuel addition to compensate for the air mass/volume. If it's an automatic XT then the RPM is up, if your downshifting, same.

The thermostat starts opening at about 170 and is full open at 196. This DOES NOT mean the engine will operate at these temperatures. The full open temp allows for maximum coolant flow while maintaining engine temps sufficient for assisting in combustion efficiency. The type of thermostat in boxers is a HUGE factor. One 170 thermostat is not like the other. The stats port sizes will be different. A Motorad thermostat will not allow the same volume of coolant through as the OEM stat or one of the 3 equivalent. So coolant flow is a factor.
The radiator efficiency is dependent on the fins being free of debris, no restrictions in coils and the volume of air going through to dissipate heat. With AC on and the heat from the condenser being pulled past the coolant radiator the efficiency rate is altered. Efficiency drops in relation to the temperature of the air flowing across it and the air is being heated by the condenser with the AC on before it travels through the radiator.

Then the fans. The fan speed is regulated based on engine temp and AC operation and pressures. Since the fans are electric the computer phases the fan operation to manage electrical load in the system. The fans will phase dependent on AC pressure running slow with low high side pressure and increase in speed when pressure rises. The fans also slow down when you're moving. This helps with alternator operation and battery life. Reducing the electrical load also reduces the engine load. It is unnecessary to run the fans at full speed when a lower speed can manage temperature efficiency. Keeping the fans on a higher speed would move more air across the radiator, but in this case it would achieve very little while increasing alt and engine loads. You may see a slight engine temp variance.

Wiring in a separate relay and sensors for the fans may cause a MIL. I'll have to look and see if this gen monitors fan operation.

Installing a larger volume radiator will not affect temperatures much. The cooling system will continue to move a specific volume of coolant in relation to the degree of thermostat opening. The coolant volume in the radiator and the volume able to remain in the radiator longer for heat dissipation increases and brings the radiator temperature down but temp variance would have the thermostat opening and closing at a higher rate. The movement of the lower temp coolant will be restricted by a closing thermostat. At the same time the engine would run in the same manner as it does during a warm up. Constant swings in engine temp will affect combustion and fueling. This will ultimately affect the overall efficiency of the catalytic converter.

There may be other factors going on with engine performance that you aren't aware of yet. The temperature under boost could be due to detonation events and the computer trying to manage it. You could have fueling issues that have the engine running too lean under boost. Spark plugs make a difference. (This engine has a 30k miles interval.) Then there's the condition of the timing belt. Off a tooth on either side, or any cam, puts the engine out if balance. (This engine has a 60k belt interval.)

My suggestion to you is log engine data from the car and insure proper operation under all conditions. Fuel, air, fire; what's occuring and how it's being managed. If you want a lower engine operating temperature, or be able to maintain temp around 200 even under high boost, then install a FMIC and replumb your charge piping. A FMIC will reduce your IAT, most times closer to ambient, and bring down the combustion temperatures.

Next would be a retune of the ROM. Change the OL and CL fueling and ignition to manage combustion temp and power output more efficiently than the stock tune designed for emissions management. But doing this only works if the engine is running properly; no issues. This goes back to data logging.

Rom Raider is an effective tool. You can record and post data for us to analyze and help you have a better running XT. The software is free, the cable (Vag-COM) is low cost. ECU Flash will let you read, manipulate and write to the ECM. You'll need a Tactrix cable for this one.
 

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2001 VDC/SC One of a Kind
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On a side note, my SC VDC temps go up under boost above 5 psi (it tops at 12 psi), it's a high compression engine (10.7:1) and I'm running a WTA intercooler, E85 and a modified ROM. My temps can climb to 225 depending on how long I maintain boost over 5 psi. As long as EVERYTHING is working the way it's supposed to, I'm not concerned with it.
 

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Discussion Starter #10
Thanks for the detailed reply.

The timing belt and plugs are new, replaced recently with the new turbo and the t-stat is new and OE, timing is correct.

I'm picking 200 - 210F as a point above the 'action temps' you mentioned ... At that temp the thermostat will be fully open, and that's also above the temps the ecu seems to care about, per the service docs I have. I.e. I don't think I'll be repeatedly walking over & back any of these temperatures, certainly not the warmup threshold.

As far as managing alternator wear, I'll just have to disagree with Subaru on this one; I'd rather cycle an addl 10 or 20 amp load to run cooler (1 or 2 fans) - chosing to wear the alt over the engine. As you mentioned in your 2nd post, you're ok as long as everything works right. I'm looking for more safety margin under heavy throttle and/or high summer temps - I just don't want to stress even synthetic oil that much.

I'll look at logging software so I have a better idea of what's really happening to the whole system - thanks for the specifics on software and cable.
 

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Did you pull your radiator when you pulled the engine? Did you look at the face of it if you did?


485372
485373


This was a 2010 Outback. The car overheated and blew headgaskets 3 times before I got my mitts on it. Even Subaru missed the above... twice.

Grab a 10mm (is it a 12? It's been a while for me..) and a flash light. Pull the two upper radiator supports and push the radiator forward to look down in there. Visually inspecting the exterior of the radiator, imo, is the first place to start.
 
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2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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You mentioned that you have an oil cooler. I think you mentioned you pulled the factory oil cooler and are currently running an air type heat exchanger. I run one of those also, however, I kept the factory coolant-fed oil cooler in addition to my air-to-oil cooler. If your oil temps are high, you coolant will also be higher.

Just a thought.
 

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Discussion Starter #15
Did you pull your radiator when you pulled the engine? Did you look at the face of it if you did?
yes and yes - but I'm taking another swipe at my oil cooler sandwich plate and will pull the rad for for more room. I'll shine a light thru all of it - that's a great method!
 

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Discussion Starter #16 (Edited)
You mentioned that you have an oil cooler. I think you mentioned you pulled the factory oil cooler and are currently running an air type heat exchanger. I run one of those also, however, I kept the factory coolant-fed oil cooler in addition to my air-to-oil cooler. If your oil temps are high, you coolant will also be higher.

Just a thought.
I removed the factory oil to water cooler for that reason. I looked at my radiator (can't remember if I looked thru) when I had the engine out and it was very clean but I'm going to make sure.

I don't think I have a cooling issue per-se, more of an ECU-controlling-the-fans quirk with the AC on -- w/ the AC off I haven't seen the temp gauge budge from the usual 9 o'clock tick.

If I don't have a blocked rad I'm going to try driving the main fan with a 200F thermoswitch and a double-throw relay:
un-energized relay ---> connect the factory fan harness wire to the fan at whatever voltage it's at;
energized relay ---> connect the fan to +12V, disconnecting the factory harness from the fan.

aside of locating and wiring the thermoswitch and relay, it's a 1-wire splice at the main rad fan.

mmmv,
-M.
 

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Discussion Starter #17
AlllllRighty-then.

Before I made any changes I wanted to educate myself on the coolant flow in the ej25 - and one of the first things the googl showed me was this:

486120


- from a vemstuning product listing to mitigate cylinder 4 running hotter than the rest due to a space around #4 which has less coolant passing by it. Some good supporting documentation accompanied the product listing.

The short explanation is cyl3 doesn't suffer the corresponding issue as coolant is diverted thru to cool the turbo - but there is no diversion for #4. Their kit is simply a tube with a T into the of the heater hoses and some fittings to tap into a bung on the head. This provides a coolant exit path for #4 back into the rest of the system.

Their product location is shown by the red arrow.

This picture brings up a couple of points - the coolant temp sensors for dash and ECU live on the crossover pipe between #1 and #2 (yell at me if this is wrong) - downstream from the water pump, just above the 'water pump' lettering in the pic above.

So any significant temp spike at #4 won't be picked up by the temp sensors - the only indication of distress will be increased knock counts for #4.

And, the sensors may be under-reporting the overall amount of heat in the system - the ECU won't be kicking the fans up until the engine is hotter than it should be.

I bought the kit which is on its way to me now. It's the epitome of 'expensive for what you get': some -AN fittings, rubber hose and a stainless Tee ... But the ability/knowledge to closely balance the temperatures in the engine is nearly priceless. Worth 'way more than the $90 kit price.

I could have well chased my tail wondering why performance was down - even with the cooling fixes planned - had I not known about this. There are several versions of this kit out there - I went with this one as it should be easier screwing just the -AN coupler into the block (and connecting to the Tee assembly once that part is connected) - than wrestling the others' 1-piece solutions into place.

So. That's going in late this week.

As I deleted my oil--->water cooler I'll also be plumbing into its (replacement) coolant bypass line a manifold with a 210F thermoswitch for later installation of a 3'rd radiator fan. I really only want to drain all the coolant once.

This:
486121


in an earlier post I'd thought of splicing into the main rad fan to force it on when things got to 210F -- but looking again at the schematics I realized I'd be breaking the low-speed drive to the 2'nd fan. This seems the simpler path and the new 3'rd fan will be placed to pull some air thru the outboard oil cooler.

mmmv,
M.
 

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Discussion Starter #18 (Edited)
The vems cooling bypass line and water thermoswitch are in - and for like the 3'rd time I gave myself a bath in coolant after forgetting that my oil cooler bypass line is lower than the radiator drain ...

That aside, the vems line wasn't a bad job once I found the plug to unscrew on the back of the left (USDM driver's) head. Word was that it's put on with some serious threadlocker at the factory, probably the same stuff they use on the cam gear/pulley bolts.

getting to it is a bit of a faf but the right combination of extensions and wobbles got me there - The breaker bar had some room to move maybe 10" - 11" back from the plug and it cracked on the first hard pull. Much easier than cam pulley bolts.

Getting the 6AN adapter fitting into the hole was pretty easy.

I had some question as to which heater hose to tap into - it's the top of the 2 @ the firewall, with the triangle/arrow pointing forward -- the return to the water pump. There's a 4" section that parallels the firewall which is the suggested place to insert the tee. Cut in the middle with a hose cutter (it's a bit tight), the tee went on with silicone and some effort; 2 clamps and it was done.

Tightening the 6AN fittings together was a challenge as there was only room for a small crescent wrench. I suspect a short 11/16th wrench would have done; 17mm was a touch too small.

Just realized I didn't post a pic of the bypass line ...
487185


Good components and they made a great case for its use.

The thermoswitch showed in the prev post also went in. I'd used 7/16" line and so the fit on the hose barbs was tight but it went on and so far no leaks.

I'd started to McGyver a fan mount but saw what Spal had to offer and ordered 4 mounting strap-things to slot into the fan. Ordered those last of course and so the fan install waits.

I'll do the wiring to/from the thermoswitch while waiting for the fan mounts - as well as insulation from the heat of the crossover pipe (!) - don't want it confusing things.
 

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Discussion Starter #19
Everything is in and almost done - I'm not happy with sensing the water temp off of the oil cooler bypass line: for some reason the temp changes pretty quickly there.

I took fan power directly from a fuse added to the battery. That is switched with a relay which runs on accessory power - I found a line in the under-hood relay box to splice into. I added a separate 5amp fuse for that. The relay mounts just in front of the fuel lines, onto a mounting screw into the intake manifole, already holding a bracket.

ACC power goes to the relay and its ground is switched thru the thermoswitch.

In-progress and final pictures - nothing on the underhood wiring as it's tucked away and the visible stuff doesn't look like much anyway.

Fan location:

487708



2 upper mounts: left goes into an existing 6mm threaded hole, right into a clip-nut. love clip-nuts.

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And tidied up:

487710



I picked the passenger side to help out the oil cooler -- which brings me to moving the thermoswitch.

It's going to move to the lower radiator hose - the inlet for the water pump. I want the 10" Spal pusher fan running if the radiator water is too warm. My assumption is there's no point in monitoring it at the upper hose as the return water from the engine will always be hot - it's the temp of the water going into the engine that matters.

And the extra fan will pull heat from the oil cooler and put some of it right back into the A/C and radiator. the amount of oil cooler area covered by the fan is quite a bit less than radiator area covered and so I thing it'll still be a win.

And I want some more air thru the oil cooler if the water is too warm -- the oil probably is too.

One more bit of work to splice a tapped 1/8in NPT adapter into the lower radiator line, and re-do the factory oil cooler coolant bypass line.

And another rad drain/fill. And probably another coolant shower.
 
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