hey guys
I need help finding a minor coolant leak. when i say minor i mean i see one or two drops gathered at the bottom of the sump after the end of a drive but not enough to leak onto the road (and i don't need to top up the reservoir).

so far i've replaced the clamps for the two hoses that come out the top of the thermostat (4 clamps, see pic) and i've also replaced the clamps on the hose further up that pipe, sitting behind the ac compressor under the intake manifold (short 4" or so hose, see second pic). But the leak continues.

It's not a big issue but i would rather prefer to find the source and fix it than leave it.

Notice in the first pic the coolant travelling down the outside of the hose.

where do i look next?

thanks in advance

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Just check to make sure all your clamps are tight. Not with a screwdriver, but with a 1/4 drive socket wrench or similar.

If you are seeing leaking on a hose like that, it would be sensible to assume it is from that hose or something in contact with it.

i have a coolant leak tester u can borrow, u can come before 12 tomorrow if u want.

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MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport

That's what I thought too right? But I have tightened each and every one of those clamps very tight with a socket wrench, not just a screwdriver...

How do they work Gordon?

Check for fissure cracks in the pipes. You'll only notice them when the car gets warm, and that would explain the minimal coolant leak. ie only leaks a little once the pipes have warmed up and are under pressure.

it slowly pressurise the system, so u can see the leak

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MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport

It's not uncommon for them to leak where the plastic top tank joins the radiator...

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No Subarus currently owned

Sometimes coolant trapped between the outlet and hose goes crusty, so no matter how tight the clamp its not a flat surface. Unfortunately you'd have to risk losing some coolant to remove the hose to clean up the surfaces.

Have a bolt wrapped in rubber glove ready to plug it. Or vice grips with soft rubber on the clamp faces.


using the Perth-WRX mobile app

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Slow is smooth and smooth is fast.

Thanks guys, had it pressure tested and nothing obvious showed up, oh well