[Ben]

Such a strange issue.

What causes the overflow to get sucked back into the system once the car has cool down?

I assume it’s when the coolant cools down the pressure creates a vacuum effect and sucks it from the overflow?

[Ben]

I am not sure how to check if its a blend door issue or not – the cabin filter appeared fine the last time I checked it. Not clogged up with debris.

In the past I have had the passenger side full heat and the drivers with no heat.

[Ben]

I have previously flushed the heatercore – ran the hose through it and it seemed to run through fine..

Its strange because the drivers side is boiling heat and the passenger side is luke warm at best.

[Ben]

[quote=”nightflyr” post=196950]I can only assume it ends up there from combustion….
A combustion gas test on the radiator will either prove or disprove this.
If positive, then you know what needs to be done.
If negative, then your likely dealing with air entrapment.
As I said, might remove the T-stat and see what results you get.[/quote]

I have this head gasket test kit – https://www.ebay.com.au/itm/BLOWN-HEAD-GASKET-TEST-KIT-LIQUID-INTELLIGENCE/181472806823?hash=item2a409f47a7%3Ag%3AAEMAAMXQUmFSis9W%3Asc%3AAU_Regular%212000%21AU%21-1&_sacat=0&_nkw=head+gasket+tests&_from=R40&rt=nc&_trksid=m570.l1313

Have used it in the past and its come up with a negative result, I will try using it again though.

I drove the car again today, I checked my overflow bottle prior to starting the car and noticed it was down to the low mark (was previously full).

Pressurized the cooling system again and found a very small weep coming out of the turbo coolant hose, nipped up the hose clamp, also tightened the bottom radiator hose clamp too.

Wet everything down with clean water to help remove any coolant residue to keep it easy to see leaks – then drove the car.

Temps seemed alright, got a max of about 95-96c.
I took notice of the heat while doing up and down hills, it didn’t change heat but I now noticed that only the drivers side is getting hot and the passenger side is cold/luke warm.

When moving the temperature dial from hot to cold the passenger side is freezing and the drivers side is a luke warm – I want to say it would be very unlikely for my heatercore to be “half” hot? But maybe this is the cause for my strange temperatures?

[Ben]

Both hoses are getting warm at the moment.

Interesting theory re the air/heatercore. Makes sense, but shouldn’t it just slowly work itself out during my normal driving ie going up and down hills and varying rpm you would think it would get dislodged and come good. When I pulled over to inspect everything I noticed some small bubbles coming through my overflow – assuming this is just air being removed from the system.

Maybe tomorrow when I drive the car it will need some topping up due to said bubble and ill be good to go?

Otherwise, if i keep getting air in my cooling system I can only assume it ends up there from combustion….(Hope this is not the case!)

[Ben]

[quote=”Tods213″ post=196920]Oddly enough, I just finished reading a forum where a guy had the exact same problem on his Subi. Even tried bleeding it on stands as well.
https://mechanics.stackexchange.com/questions/22000/blocked-water-flow-in-engine
Just offering this as a theory but perhaps your radiator is the culprit. I’ve had it happen only a few times; at higher rpms your radiator hose can actually suck shut. Its not because of too much restriction in the system, but because of too little restriction.
Glad your leak down test went ok, best of luck.[/quote]

So I ended up putting in a replacement used radiator from the parts car I have (same car but auto). This radiator was a genuine style one.

Temps are down a little bit, it seems to be cooling better then the eBay spec one.

I am getting about 90c just normal driving, but the odd thing was, that when I was going down hill the temps would start to drop quite a bit, down to 80-82c.
Now any normal car will drop temp during a down hill, no/minimal load and the rpms are up for engine breaking. I thought i would try shifting in netural to take the rpm’s otu of the equation and the cars temp still went down.

I tried it while coasting on a 100km/h stretch of road, sadly it did not do the same thing, it seems to be related to the angle of the car. Up hill the cars temps would go up, with 97c being the most I saw going up hill. Mind you these are still light throttle/load applications.

The temps did not spike down 10c after hard acceleration with this radiator installed and the bottom radiator hose is now hot.

Ideally in the 80c range would be where I want the temps to be during normal freeway type driving.

I am a little confused bout the down hill driving and how it would cause the temperatures to come down quite quickly – perhaps there is a flow issue somewhere?

[Ben]

Hmmm, The radiator is new – but it is a cheap eBay spec alloy radiator.

Not sure if its worth purchasing a new one yet or not.

[Ben]

Thanks Nightflyr,

I ended up draining the coolant, removing the thermostat and testing it in some boiling water. I had a thermometer on it and it began to open at 78c and was fully opened by 85c-90c, can’t remember the exact figure but I believe its working no issues.

While it was apart, I ran some water through the two hoses that get to the thermostat (the bypass), one went through no problems, one was a little slow but still flowed down.

This was the turbo side.

Everything else seemed ok, put it all back together, bled it out with the funnel and after quite sometime the bottom hose got hot! Awesome…so I thought.

The temps never got over 95c-96c while doing this.

Took it for a drive and unfortunately it is the same issue. I will be doing 100km/h and the car will be operating at about 95c-96c, pulled over and felt the bottom hose was cold again – what the F#$%?!

I noticed while giving the car a decent wack of throttle the temp would spike by about 15c, I saw it drop down to 82c (which is where it should be), but then within less a minute it was back up to the mid 90’s.

I am thinking one of the hoses that heats up thermostat might have some kind of restriction or kink somewhere to have such low flow….then when the RPM’s/Load increases the waterpump pumps harder and forces the coolant through, in turn opening the thermostat.

Just a theory anyway.

[Ben]

There is pressure in the hoses when the caps are on.

I will admit it is a cheap eBay style radiator, but It flows no issues the last time I ran the hose through it.

[Ben]

Yep thats with the car at operating temperature, Have pulled over multiple times to check while driving and even let it warm up stationary and the bottom hose never got hot.

The radiator is less then a year old and is a alloy style radiator.

I have let the car get right up to operating temperature with the radiator cap off with a spill free funnel on the expansion tank – squeezed both upper and lower hoses to no avail. Bottom hose still cold.

[Ben]

Here are the results from the leak down and pictures of the spark plugs.

Drivers side rear, 2% leakage. 90 psi in 88 psi out
Drivers Front, 90 psi in 87.5psi out
Passanger rear – 90 psi in, 90 psi out
Passanger Front – 90psi in, 90psi out

So looks pretty good to me – No bubbles could be seen in expansion tank during the leak down, fingers crossed I am in the clear.

While I was under the car, i noticed a small dab of coolant on my sub frame…

Upfron further inspection I found a leak! (Actually found three) – Just to confirm they were indeed leaks and not just spilt coolant, I wiped everything up and pressurised the system. Sure enough they started to drip.

So I have tightened up the clamps on the leak points and so far so good, pumped it up to about 17 psi and left it for about 25 minutes. It dropped half a psi of pressure, I assume this is pretty normal amount of pressure loss?

Now I believe I have another issue – the car seems to be running a tad on the warm side. I have a gauge reading the obd2 coolant temp, from my general reading (especially in our current weather – winter) mid to low 80c is normal during high way drive (100km/h) but my car is reading about 94c.

The temp drops radically during higher rpm driving (hard acceleration) but during normal cruise rpm the temp creeps up to about 94c.

Keep in mind the fans turn on at 97c, having a car driving at 100km/h with the fans on is not right.

My bottom radiator hose is cold and not warm at all, as is my thermostat area.

Any ideas on what could be causing this?

Some pictures 🙂

Subaru Diagnostics, Coolant Leaks and spark plugs

[Ben]

Alrighty fellas, you have give me some motivation to get back into it.

Currently have the car back on the lift, have removed a spark plug, got it on TDC and put my leak down tester on it.

So far so good, 2~% leakage, 90psi in and 88psi out on one cylinder.

Three to go!

Spark plug looked normal, will post up some photos of each plug though.

For reference, the rad caps are fairly new (within 6 months old) as I replaced them initially when I started loosing coolant.

[Ben]

There is some smoke out the tailpipe during startup (looks like water vapor), but it is our winter time here so it could be condensation, hard to tell. It does clear up once the car is up to operating temperature though. So it is not there all the time.

[Ben]

The turbo is water cooled, but I have tried another turbo and it did not make a difference…

Would it be possible to determine the cause for consumption without removing the engine again?

[Ben]

Also the car is a manual, so no coolant going through the gearbox.

Is it possible I can have coolant loss if my cylinder heads and head gasket are ok ?

I don’t believe turbo chargers can consume coolant?
Bad short block?

[Author]

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