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]

Lets keep things simple.
Your loosing coolant.
If your 1000% sure there is no external leakage thru testing.
Your left with:
Coolant being burned in the combustion camber.
Coolant being passed to the oil
Coolant being passed to the transmission
Coolant being passed to the intake.
FWIW..
Just because new or reconditioned parts were used does not promise them to be 100% fault free.
Just something to be considered.
It is also possible something done during the reassembly was done incorrectly.
I’ve seen where a set of head gaskets were installed upside down.
A second tear R & R was done by another shop and they installed the replacement set upside down also.
Anything is possible.

[Ben]

Thanks for your reply!

I agree, it has to be going somewhere.

I personally put the heads on the block both times. Following the factory service manual and ensuring everything was correctly prepped and cleaned prior to installing the cylinder heads.

I do not believe coolant runs through the intake in anyway on they engine, it used to run through the throttle body but I have bypassed it.

It’s just a shame that I have gone through all this work to ultimately do the job a third time, but I am still not 100% sure on how the combustion is getting into the cooling system with everything that has been done so far.

Something isn’t adding up.

[Richard Kirshy]

Have you done a combustion gas test on the radiator?

[Ben]

I did this after the first rebuild, it came out negative.

I will try it again on the current build.

[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?

[Richard Kirshy]

Is it possible I can have coolant loss if my cylinder heads and head gasket are ok ?
A crack in the cooling jacket
I don’t believe turbo chargers can consume coolant?
That depends if you have a water cooled turbo
Bad short block?
Anything is possible.
You may also want to check for possible leaking hear.

Attachments:

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[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?

[Richard Kirshy]

Ok, you said your now smoking out the tail pipe and absolutely no signs of any external leaking.
I assume white smoke (coolant being burnt)
If so, you might try removing the spark plugs.
First look for extremely clean (new) looking electrode(s)
That is a sure sign of coolant burning.
You can also use a bore scope to look inside each cylinder.
If any look extremely clean or appear wet, chances are they’ve been burning coolant.
As to the source…..
If either of the above is true, unfortunately you’d be looking at the very best a bad head gasket(s)
Defective head(s) or block.
Unless you have some bizarre quark with turbo cooling.

[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.

[Richard Kirshy]

This is what burning coolant typically looks like in cold weather.

What your describing sounds normal.
Could be as simple as this:

[Todd Smith]

I noticed you said the coolant system slowly loses pressure when you test it. Why not pull the spark plugs, pressurize the system for a while and see if it bleeds off into a cylinder? Either it won’t and you’re internally in the clear or it will and you’ll at least know where to look when you pull it all back apart. If you have a borescope, you can watch it happen in real-time. Otherly, you can wait a while and crank the motor over and watch the coolant come out of the offending cylinder.

[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]

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

[Richard Kirshy]

First thing
FYI, it is not uncommon for a new / rebuilt engine to run warmer than normal until every thing is seated in.

That being said…
My bottom radiator hose is cold and not warm at all, as is my thermostat area.
Is this with the engine @ operating temp?
If so, My first thought is either a flow issue or air entrapment.

[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.

[Author]

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