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Old 11-23-2020, 07:10 PM   #1
f4phantomii
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Default Help locate a coolant leak on 2004 STi

2004 STi with 163k miles, no mods.

There is coolant dripping down through the holes in the jacking plate right in the middle of the engine. Just aft of the oil pan.

There is no smoke or steam, nor any odor of coolant cooking off, so I don't think it is coming from anything on top of the engine.

But I cannot find the source.

What are some possibilities for coolant leaks towards the back/center part of the engine?

Heater core?
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Old 11-23-2020, 07:59 PM   #2
Vancouver98STi
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There are no doubt more, but I'm aware of coolant lines that connect to the throttle body.
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Old 11-23-2020, 08:45 PM   #3
snow_bound26
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Check the heater core hoses and the coolant crossover pipe as well. I know you stated it's not smoking but it wouldn't hurt to check the coolant line feeding the turbo.
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Old 11-23-2020, 09:05 PM   #4
f4phantomii
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I assume I'll need to do most of these from below?

I've looked all around the turbo and no evidence of leakage. Nothing is wet that I can see.

I've got a fiber optic wifi cam someone gave me. Over the holiday I may roll it out into the daylight and do a systematic search and pray it isn't a head gasket.
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Old 11-23-2020, 09:21 PM   #5
BlueSTI4Me
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If none of the coolant hoses have been serviced on your car, you need to service all of them. I suspect the heater hoses leaking, best way to view them is intercooler removed.
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Old 11-23-2020, 10:08 PM   #6
f4phantomii
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Quote:
Originally Posted by BlueSTI4Me View Post
If none of the coolant hoses have been serviced on your car, you need to service all of them. I suspect the heater hoses leaking, best way to view them is intercooler removed.
Thanks. I'll pull it and take a look.

The upper radiator hose was replaced when I had to replace the radiator about 6 years ago.

I'm the original owner so I know all the other coolant lines are original.
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Old 11-24-2020, 12:14 AM   #7
BlueSTI4Me
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Quote:
Originally Posted by f4phantomii View Post

I'm the original owner so I know all the other coolant lines are original.
Original owner of a 2004 here as well and I will say those original hoses are ticking bombs. I would replace all of the coolant hoses if I were you. I like to keep them fresher than about 5-6 years old personally. And I only like to drain refill the cooling system once. But that is me.
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Old 11-24-2020, 06:52 PM   #8
Elbert Bass
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Odds are if you have a hole in a hose or coolant line. As metioned there are hoses on the left for the heater core, and on the right for the turbo that can leak down the crossmember. The easiest way to locate a coolant leak is to pressure test the cooling system. Many auto parts stores rent a cooling system pressure tester (make sure they have the Subaru adapters with it).
You can pressurize the system to 15 PSI and then usually it won't take long to trace it back to the source. The engine doesn't have to be running or warm to this test. Make sure you start with a full cooling system - if the coolant level gets lower than the leak it will quit flowing.
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Old 11-25-2020, 01:46 PM   #9
f4phantomii
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Ok...I pulled the intercooler this AM and it was not the heater hoses.

Being this was my first opportunity for a daylight inspection I cranked it up. Still coolant leaking all over the place.

I finally traced a leak to the very short hose between the upper coolant reservoir and the turbo housing. Looks like could be just a loose clamp.

So I'll deal with that and hope I didn't just create that leak when I removed the intercooler.
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Old 11-25-2020, 02:27 PM   #10
f4phantomii
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Aaaaand fail. I suspect I created that leak removing the intercooler. It's fixed.

I'm suspecting the water pump again.

I can't see a leak, but there is coolant dripping from the bottom of the water pump. And coolant is running along the flange of the oil pan. That appears to be how it is getting aft to drip onto the jacking plate.

It doesn't look like a head gasket leak, but i can't see the top side of the head.
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