Turbo 2.5 L Subaru Loosing Coolant, but no visible leaks? Fresh rebuild.

[Ben]

Hey all,

I have a MY09 Subaru Forester XT, and I am about at my wits end.

Long story short;

The car over heated due to a air lock from replacing turbo’s.

Engine was pulled out, heads were sent off to be reco’d

Purchased a brand new shortblock and put on the reco heads

same thing – still loosing coolant and now smoking

Took the engine back out – got the heads checked over again, machine shop found a crack that said was near a oil gallery and exhaust valve (they did not pressure test the heads during the reco), so could be my issue for smoking. but were not confident it would cause coolant loss.

Sourced another set of heads, they were pressure tested, tested ok, then everything was reco’d again.

Fresh gasket kit, used the same shortblock.

Same thing – Still loosing coolant.

Current setup;

2nd set of Reconditioned heads

Brand new STI Shortblock EJ257, would be 2.5 tanks of fuel old now.

Silicone Turbo Inlet

PCV valve Deleted, crankcase and valve covers venting to atmo till can sort this issue.

VF52 Turbo (have put the stock TD04 on as well, same stuff)

ARP Head Studs, toruqed down in three steps to 90 ftlbs as per instructions, in sequence shown.

Genuine head gaskets

Air Pump/TGV Deletes

Throttle body coolant bypass (used little rubber caps on the two lines)

Where do I go from here?

The bottom end is brand new from subaru, the heads have been reconditioned and I have been assured these ones have passed the pressure test.

Is there any other way I could be loosing coolant? I have vacuum filled the system (and manually burped the system) and pressure tested the cooling system to see if i could find a external leak, I can get it up to about 17psi (just before the rad cap opens) and it will drop a psi every two minutes or so (didn’t time it exactly).

I can see some little bubbles in the expansion tank through my spill free funnel when I run the engine when burping the cooling system, but I find I will be burping forever…

Car seems to drive fine, just needs about 100ml in the overflow bottle after almost every drive….not right for basically a brand new motor.

Any idea’s? What could cause air in the cooling system?

Topic

[Richard Kirshy]

That ain’t right!!!!!
Do the hoses have any pressure in them or do they feel empty?

[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.

[Richard Kirshy]

Well you either have:
Air entrapment
No flow from the water pump
A massive blockage.
My guess is that you have air in the system.
Even though you vacuum filled the system….
Might try raising the front of the vehicle so that the radiator cap is the highest point, attach a spill free funnel rev the engine @ 2 – 2500 RPM with the eat set to hot and blower off for 10 minutes.
Another thought, install a PRESTONE flush kit then back fill the system through the tee adapter.
Some vehicles are a bear to completely bleed
As a last resort…
Just for giggles,
I would pull the T stat and see if you get flow.

[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.

[Todd Smith]

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.

[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]

[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?

[Richard Kirshy]

Lets apply a bit of simple mechanical logic here..
Going down hill, the highest point of the cooling system would be the heater core.
If there is air entrapment it should rise to the highest point.
Now if the heater core is basically isolated from the rest of the system by a air bubble, the engine cooling should work as usual.
When the vehicle is on level ground the air works its way back to the block and causes your issue.

You should be able to prove this:
Repeat your down hill test drive and confirm the temperature readings.
Then do it again, but this time have the heater on full and see if heat coming from the vents.
If not, you proved air entrapment.

Another test would be to remove the thermostat and try driving and check to see if both upper and lower hoses get warm.

[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!)

[Richard Kirshy]

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.

[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?

[Richard Kirshy]

Low heat output from the heater core has pretty much two causes:
Partial blockage
Air pocket.

[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.

[Richard Kirshy]

Are you sure the blend doors are functioning correctly.
Is there something blocking the air flow on the passenger side.
Has the cabin air filter ever been changed.

[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.

[Author]

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