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

[John Kirkham]

In all this searching for an answer the water pump has never come into it I had ridiculous issues with temps and cabin heating issues and my local garage advised that sometimes the plastic impellar on the pump can slip on the shaft when hot causing all sorts of problems it was a jag v8 so completely different I know but you never know I fitted a new pump and everything was sorted

[Richard Kirshy]

Glad to hear you have it sorted out.

[John Kirkham]

Thanks yes an easy fix and it only took about 20 mins to do it was just a thought and hoped it might help,another problem I once had with an alfa with a boxter engine was that there was a rubber coolant pipe that ran along the top of the block underneath the inlet manifolds that engine vibrations rubbed a minute hole in that leaked when hot and pressurised that caused coolant loss but was hard to fin as the leak was straight on to a hot engine block and simply evaperated off

[Ben]

I havn’t really considered a defective pump.

I have used GMB pumps on two other builds along with there tensioner’s and have not had any issues.

It looked pretty similar to the pump that was on the car prior the shortblock replacement, but I will take the timing covers of when I remove the thermostat and see if i can find anything of interest.

[Ben]

[quote=”nightflyr” post=197000]Sounds about right.
Subaru has an odd layout for the way they route their coolant.
Please post the no thermostat results when you get them.[/quote]

Just thinking ahead of time here there will be two results I guess without running a thermostat.

1. The car will overcool
2. The car will have similar temps as when it was running with a thermostat.

What do each of these results mean or lead to indicate?

[Richard Kirshy]

[color=orange][i]Just thinking ahead of time here there will be two results I guess without running a thermostat.
What do each of these results mean or lead to indicate?[/i][/color]

1. The car will overcool
First…. assuming you bypassed the heater core.
Second…. you’ve confirmed the engine passes a combustion gas test done according to the instructions
Air entrapment
Issue with the thermostat.
It should run over cooled with no restriction of the thermostat.
Next step beyond that would be to hook up the heater core and repeat the test.

2. The car will have similar temps as when it was running with a thermostat.
Then there is a serious circulation issue and would suspect a faulty water pump

[Ben]

Results are in.

Have ran the car without the thermostat.

The temperatures were colder in the downhill idle conditions, but soon as throttle was applied the temperatures did the same thing – it took longer to get there due to no thermostat but ultimately if I mimicked the same driving conditions the car would ultimately reach 96c at 100km/h.

I ran water through the hoses with a funnel and everything seemed to flow well. I put the heater core back on and it has made no difference to the operating temperatures.

[Richard Kirshy]

In that case you either have:
A faulty radiator cap or incorrect pressure rated cap…… You might try pressure testing it.

A faulty water pump…. if the impeller is slipping on its main shaft at higher RPM you will have reduced coolant flow through out the system.

[Ben]

While the car was on the dyno – the tuner reported the temps were going up under higher rpms.

He said in his experience the temps generally stay the same or drop due to the water pump working harder as the rpms increase.

I will try replacing the water pump I think

[Ben]

Alright in a last ditch effort to at least try and rule out a potential radiator or water pump issue, I tried to do a flow test. I did a little experiment this arvo – not sure how scientific and what it proves, but check it out and see what you think.

I am not sure what kind of flow rates a water pump should have – but should it be more then this ?

See these two very professional video’s and see what you fellas think;

https://youtu.be/7PSeQBzM_Us

https://youtu.be/_b4XfXjfQhM

[Richard Kirshy]

I can not say what the flow rate should be to the turbo.
But you should repeat that test for the input side of the radiator itself to see the true flow of the water pump.

[Ben]

Hmmm, the inlet of the radiator (top section) hoses are quite large.

Will have to do some thinking on how I could rig up a similar test.

[Ben]

[quote=”nightflyr” post=197123]I can not say what the flow rate should be to the turbo.
But you should repeat that test for the input side of the radiator itself to see the true flow of the water pump.[/quote]

OK, I setup another messy test on the car.

Video to come shortly, but the way its looking I don’t think its the water pump – perhaps I just have two poor heat dissipating radiators.

[Ben]

Videos are up –

Test #3 – https://youtu.be/zViwK2j6mOM
Test #4 – https://youtu.be/xivlclB_ZHs
Test #5 – https://youtu.be/nr4p5MbXnk4

Test #4 Video explains it in a bit more details, but basically I have disconnected the radiator inlet hose and just wanted to see how much it would “Flow”.

I didn’t have enough water flow to actually keep it going, so the tests do not last too long.

So I believe things are pointing towards the radiator now…

[Richard Kirshy]

Perhaps…
Your method of testing leaves questions to the results.
To begin with your introducing air into a sealed system.
Secondly, your never seeing a flow rate when the engine turning at the same RPM as when you experience the issue.

First suggestion to test the flow of the water pump that will allow you to:
1 See the true flow rate at idle and speed (which is where your issue occurs mainly)

Next will allow you to see the flow through out the entire system again at idle and speed

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