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First, not a mechanic. Cars baffle and intimidate me, but I'd rather learn something than pay lots of money for someone else to do it... perhaps not a good thing... Looked (researched?) all over the internet. Finally decided to start my own post...


Overheating issues - seems to happen mostly when going uphill, but it's been hot lately and has also overheated after a few minutes on the road. Just started maybe a week ago, and progressed quite quickly. Not it'll do it every time.


150k miles

(No idea as to the history of the car, but I'm sure the guy who sold it to me was kinda shady, after multiple issues (electrical), I noted that the CEL light should be on... when I looked closer there was some black electrical tape covering the damn thing! Yikes!)


T-Stat - Replaced thermostat w OEM from the dealer

Radiator Cap - Replaced Radiator Cap with a Cheap-O, but as coolant seems to rise and fall in reservoir, I don't think this would be the issue.

Head Gasket - Used a NAPA block test kit, seems okay (liquid stayed blue). No visual signs of leaking head gasket under the engine, that I can tell.

Air - I think I've bled the air out properly after t-stat replacement, well enough, I hope.

Water Pump - Not sure, I think it's working. If I run it without the radiator cap on, the coolant level rises until the fans cool it back down. The temp  seems to cycle normally, if I rev it up to about 2000+ rpm, the lower hose collapses... I'd assume the pump is causing this to vacuum... both upper and lower hose are tight with the cap installed.


At idle, fans turn on at 203 F (read live via ECM), cool to about 190 F, and then cycle as such. This will continue if I hold it at about 2500 rpm as well. If I hold it at 3700 (high, I know, well, I think... sounds high), she'll overheat. I hit the red mark at about 235 F... so I stopped at about 225 F


Coolant seems to pulsate up and down, as far as flow goes, can't really see it moving in this radiator design...


I'm thinking the radiator possibly? Is there something I can do at home that will verify a clogged radiator? Oh ya, just to note, there was only water in it before I replaced the thermo.


Thanks for any tips you might have, and for your time as well.

Edited by beamsbox
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good research and testing already, well done, you don't give yourself enough credit. 



a clogged radiator generally has very specific symtpoms - not random.  So it'll overheat uphill or only in the day and not at night - it's notably cooling load depending.


the only test i've done is to pull the radiator and run hose water through it - it will flow notably less than a non-clogged one.  but without another radiator around to compare it too that may be an abmiguous thing to determine.


look for bubbles in the overflow tank - even right after you turn the car off, check it multiple times - is there a slow source of bubbles in the plastic overflow tank?


original headgaskets on that engine usually fail externally - they start seeping and progressively get worse externally.  internal failure of OEM original headgasket is very rare.

but of course prior overheating if significant enough can cause any symptom if it's bad enough.


you did the proper check - the block tester will tell if exhaust gases are pushing into the coolant.  usually only a symptom of older 90's subaru engines or non-OEM headgaskets or frequent overheats of the kind of engine in your car.


That it had only water in it suggests something more ominous or maybe that's common there where it never gets below freezing?


that engine also requires a bottle of Subaru Coolant Conditioner.  with only water it may not have the conditioner and i dont' know if the conditioner "requires" coolant to work properly...probably not?

either way - if you get it fixed be sure to add a bottle, $2.50 at the dealer (well everything is more expensive in Hawaii so maybe a bit more).

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thanks GrossGary,

No bubbles in the overflow tank. No milky oil.


Symptoms don't seem random at all. It'll overheat under load, but not at idle. I could probably drive around all day in town. Hills get me. At about the same point every time.


As for water in the radiator being a norm here, everyone says just take out the thermostat... that's their fix, I guess. But I did replace the water with 5050...


Do I need to pull the radiator to see the flow? Maybe I could just check it in place? But even then, I don't have a good one to compare it to. I've read somewhere that like 13-18 (?) gal. per minute could be considered normal. Which is really fast in my opinion... so if it's a bit sluggish that could be the cause...


And yup, everything is more expensive here, lol. Everything. ;(


Should both radiator hoses be Hot HOT? As it's running hot? I'd think there'd be a difference. But my fingers can't really tell.

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it's normal for the A/C to shut off when engine temps get too hot.  they all do that.


i'm uncertain of hose temps.


the one clogged radiator did the same thing for me - over heated on hills. 

it also only overheated during the day when ti was hot and not at all at night when it was cool.  does yours have that distinction?


you could try and test it in place, it just got water every where for me and i wanted to directly compare with another one lying on the ground.

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I'd say yes, when the temperature is above say 80 (which is all/everyday right now) it doesn't overheat. After the first time it overheated, I made it over the pass multiple times with no issue, at night perhaps 9 or so. Wonder how much a flow test would be. Do you know if they remove the radiator for the test? Cause if so, I'd rather do that part myself and just take it to them, lol.


thanks Gary.

Edited by beamsbox
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My scanner says no codes to display.

Is it normal for the driver side of the radiator to be much hotter than the driver side? Just drove it up 'the hill.' Got hot. Pulled over and let it cool a bit. Noticed the temperature assymetry. Started it and let it idle. One side is much hotter than the other.

Edited by beamsbox
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sound suspicious.  i wasn't able to clearly pinpoint the clogged radiator like that.  mine had so much heat everywhere and blowing around from the fans my infrared temp gun was useless and the hand method wasn't telling me anything either for some reason.  maybe the bad spots just weren't accessible or something.


but if you're seeing a notable difference that's fairly suspicious!


Subaru radiators on the main land are routinely around $100 and can be ordered online where you enter TRT41 in the discount code of Advance Auto parts and get $40 off $100 - so they're $60 bucks.  A legacy one just two weeks ago was $99 so with a jug of windshield washer fluid just to hit that $100 mark.  So $60 for radiator.


i don't remember any hills on Oahu?  are you hitting the kava before posting?! ha ha

Edited by grossgary
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I'm from Alaska, so it's definitely not a mountain... perhaps the foothills would be a better term, lol. up on Tantalus, nice lookouts over Honolulu, where the house prices jump from 600k to 4 mil. Phew!

As for the radiator, I just felt both sides a bit. My wrist noticed that with the AC on, the high side of the AC system passes by the right side of the radiator. Hot! So, I turned off the AC, let it cool down a bit, and felt it again. As it was reheating, the driver side (at least where I could reach with my fingers) was much hotter. Using my calibrated fingertips, I noted that the passenger side took a few seconds to burn, whereas the driver side burnt me real quick! Haha! So, I guess that's the method, at least in my case.

As for Kava, nope. The neighbor who made that stuff and sold it to me for cheap just moved back to Micronesia. Not like I drank it much though, that stuff wears out my stomach lining or something...


John, I'm hoping that's the case... well, kind of.

I noticed that there's some silver-metallic particles which seem to be immersed in a thick gray substance (It's built up on the reservoir cap), and after I put coolant in, I noticed the particles floating around in the coolant, tiny little guys. It did cross my mind that these could be what stop-leak might contain. Do you know if there's anything like that? I'd say the reservoir cap has something that looks kinda like a watered down copper anti-seize,,, but the particles are silver instead, suggesting that they're not corrosion from inside the radiator itself... hmmm...


As for the problem (and before I forget):

This evening, I drained out all the coolant and removed the thermostat (dipped it in boiling water to test it out - good). I used the neighbors hose to flush out the heater core, the engine, and the radiator. With the radiator I flushed it from the radiator cap, the upper hose port, the lower hose port, and from the drain valve... Note: (because others here in Hawaii have told me just to remove the thermostat) this Subaru drains quickly out the thermostat housing when no gasket is in place. I replaced everything but the thermostat and ran it (adding water every 30 sec or so) for about 5 minutes. Then I drained it all back out (dark by now at 8 PM) and filled it per the manual. (Slowly!) Can't say if any of that helped... cause its cooling down now, will update tomorrow after I top it off.


One thing I did notice though after all this (I've been touching and feeling and smelling and listening to this thing all week): Before flushing everything, the upper hose AND the lower hose were quite stiff (when pushed or squeezed), but after the flush, and after letting it heat up, the upper hose is about the same stiffness as before while the lower hose is quite noticeably softer to squeeze, and a bit cooler. Not sure if that's a thermostat opening now whereas it wasn't before, a proper fill with no air bubbles, or a radiator causing less restriction to the system... but I'm gonna be optimistic on this one (I tend to be naiively optimistic at times.). Tomorrow I'll top it off and let you know.


Thanks again for all the input.

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very thorough work, good job.


sorry to ask a dumb question but you're checking the radiator and not the a/c condenser right?  it also looks like a radiator, so just checking.


did you try running the hose in one side and note how fast it came out the other?  did it seem clogged or flowed well?

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If you decide you need a new radiator check prices at K. Ifuku Radiator--Waiakamilo Road, just makai of King St., Ewa side.  They've been quite reasonable when I needed radiators.  The mainland "Radiator Barn" type places will probably charge an arm and a leg to ship out here.  Good luck! 

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I have read stories of water pumps breaking down, with pieces of their pump fins breaking off, or what ever. Result is poor water pump performance, with resultant over heating. It may be worth your time to pull the water pump to check out its condition. It may be worth it, to just replace the water pump, as they are not that expensive.


When you drained the radiator, did you see any rusty looking water, or crud drain from the radiator? If so, that would have been a strong indicator that your radiator is plugged up. If not, then I would think the radiator may not be your problem.

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Ya... Thinking not the radiator. Does seem really hot tho, then again not moving really fast.


Never gone that deep into a Suby. Closest I've been is to replace the valve cover gaskets. Manual says you need a ST Blah blah tool to remove the cam sprocket in order to get the toming belt cover off... Besides a torque wrench, any particular (special) tools I might need to replace the water pump, or even delve into the heads myself?

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So, as to the shadiness of the guy who I bought it from... I took the car to a local Subaru guy who works on them out of his house yesterday. HE RECOGNIZED THE CAR! Haha! He said his buddy moved to town and bought the car two years ago and brought it over to him to check it out. He looked inside the hood and told him to take it back right away! Haha! So ya, I guess the guy was as shady as I had anticipated.


So basically the car's been pieced together... perhaps salvaged from an auction, quick head gasket job, new radiator, and sold... to my lucky butt.


The guy said that, since it's not really worth much, putting into it the cost of a head gasket job is kinda dumb. To get some cheap use out of it I could try the BlueDevil Head Gasket Sealant...

So, I drained it, flushed it and added the BlueDevil crap (I know..), I even cored out the old thermostat and installed it with basically just the gasket so that coolant would flow easily... 


And... No love! Still idles like a charm, and overheats with any attempt to put it under load...


Hmmm.... any new ideas?


Is it normal for the fans to kick off when you open the throttle a bit? Seemed oddly backward to me earlier when I was burping it.

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