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Discussion Starter · #1 ·
Little help please!!

I am chasing down a coolant leak and I think I found the culprit but I cannot seem to find the part , even after talking to the parts counter at the local Subaru dealer.

The leaks looks to be coming from a hard line that is located above the thermostat housing and routes up to the head on the driver side. (Pictures attached).

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The parts counter gave me the part # of 14165AA021 but when I look at the diagrams I am not sold it is the correct part #.

Does anyone know what the part is called or it's part #?
 

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Discussion Starter · #4 ·
Thanks, SilverOnyx!

What you posted definitely looks like the right part.
I am definitely chasing a coolant leak. In the second photo you will see the green and white residue on that line from the leak.

If that is an oil line , which makes sense since it goes into the head, then the leak might be coming from somewhere else. I changed the thermostat and gasket which did not resolve the leak.

Maybe next up is replacing the thermostat housing before I change the line referenced. I know it might be much but any other thoughts on where the leak could be coming from in that general area (by the thermostat housing)?
 

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If the horizontal section of the pipe is above the thermostat, then whatever is leaking at the thermostat housing would have to be a stream or spray, otherwise the coolant would more likely flow down, or back, but not up to the pipe. Perhaps there's a pin-hole in the lower radiator hose . . .

Is the stain on the pipe in the second photo just residue, or is it actually wet? Could it be a stain from an earlier spill and not related to the current coolant loss?

How much coolant is it losing?

(I don't have an H6 to look at so perhaps someone that does could see what's above that area that could leak coolant onto the pipe.)
 

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I have an H6 sedan in the garage and there's only 3 things that would put that coolant there.
One and two is the thermostat housing or hose. Either a gasket or a pin hole as mentioned by @plain OM.
The other is the water pump which sits in front of the area where the thermostat is.

I see that someone's had the front engine covers off. Do you know why? (I can see the sloppy RTV in the pic.)

Check your oil and see if it has signs of coolant mixing with it.
 

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Discussion Starter · #7 · (Edited)
Timing components (tension guides and water pump) were replaced about 1k miles ago. The oil was changed just last week and no signs of coolant.

The coolant does not leak all the time and is it not losing much. Originally Subaru said it was the lower hose but wanted $300 to replace it, so I did it myself. After I replacing the hose, the leak was still present but significantly less which is when I did the thermostat and gakset. At that time there was some white scaling on the housing and where it mates onto the block. I did my best to clean both sides with some 00 steel wool.

At this point I am thinking the thermostat housing should be replaced and maybe even use some rtv on the mating surface.

I really appreciate all of the thoughts and insight. Once I replace the thermostat housing I will update the thread.
 

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Don't use rtv on the housing. The gasket that comes with the thermostat is sufficient. I don't think it's the housing or the thermostat. If it were it would drip constantly. I believe there may be an issue with the water pump or it's gasket.

Do you have a way to pressure test the system? You may be able to rent/borrow a kit from a local parts store. This will save you time and expense on replacing parts.
 

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Discussion Starter · #9 ·
I do not have a coolant pressure checker/monitor but I am sure I could buy or rent one. Something I do not understand is , regardless of where the leak is, the tester would just show a lower than expected pressure figure. How would it help isolate/ pinpoint the source of the leak?

Perhaps it would be better to use a UV light reactivate dye in the cooling system and look for it that way?

A couple of things that make me think it is the housing is that it only happens sometimes , like maybe only when the thermostat is open and the lower hose/housing has more pressure than when it is closed. It also might be that a pinhole leak on the housing could spray the fluid onto that oil line like that.

The scaliing on the block port and housing bothered me when I did the thermostat change and maybe I need to clean it better with some CLR rather than break leen like I did with the steel wool?
 

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When you pressure test the cooling system, if there is a leak, coolant will drip/spray from the leak. The test involves pressurising the system to the normal operating pressure (16PSI from memory).

This is a common test to reveal the source of the leak. There is no dye necessary or required for this test and any leak will typically be very noticeable.

Seagrass
 
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Exactly. When pressurizing the system from the radiator cap kneck, that pressure is applied to the whole system and any leak will be seen by a spray or slow stream of coolant. You already know the area, you just have to look close for the leak.

CLR may not remove the coolant residue. Purple Power or other stringent degreaser will.
 

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Discussion Starter · #12 ·
Excellent. I see now , it is a tool that creates pressure in the systems without the car running and not a gauge that simply hooks up and shows a number. Here I was thinking it was like a compression test on a cylinder where all you do is confirm if it is less pressure than expected.

I appreciate the explanation and will get to work!

One thing I would note is when I was burning the system there was no leak and that was with the car running for like 25 minutes. With the cap off though , little pressure would build up in the system , so I definitely see the benefit of pressurizing the system w/o it running or being hot.

Thank you all and I will post an update once I have one!
 

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Here's a for instance for you.

EJ255 is leaking coolant when it's running. Faint drips are under the car when sitting but the spray under the engine didn't leave a good trail. The pressure test showed the coolant coming from behind the timing cover. Pulled it apart, has a Japanese pump installed. The leak was the paper gasket someone put on with the pump when the timing belt had been done 35k miles prior.
 

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Discussion Starter · #14 ·
So I found the leak or kind of... and am hoping some one might have a better idea of what exactly it is. The only thing I can think of is the head gasket...

The leak is above the thermostat, above that oil line that goes to the head and just a little above the general level of the water pump . It doesn't really spray and the mosture/fluid lines look to be at a spot where there is a seam.

Any help/thoughts would be greatly appreciated.

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I am thinking that may be your water pump leaking but not easy to tell.

Seagrass
 
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Discussion Starter · #17 ·
The water pump is certainly easier than a head gasket. However there are a couple of questions that hopefully can be answered. Keep in mind I replaced the water pump and gasket/oring less than 1k miles ago. Both parts were purchased direct from Subaru.

Are we saying that the new water pump is defective? That there is a problem with the gasket/oring? Below is a picture of the old water pump.

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Is there a different gasket that should have been replaced other than the black oring which is closest to the fins at the top?

Where is the weep hole? Is it the hole in the middle as pictured here?

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Again thank you for the help!
 

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Always good to have new information when trouble shooting a problem over the internet.

Yes the weep hole is the hole shown in the second picture. If the water pump seal fails, coolant leaks out tge weep hole to alert the owner of a problem with the integrated water pump seal.

If you used a new Subaru water pump it is unlikely the seal has failed already. It is more likely that the O ring seal has failed.

Before installing the water pump did you ensure all surfaces were clean and free of debris?

When you installed the water pump did you lubricate the O ring with silicone grease or rubber grease before installing?

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Discussion Starter · #20 ·
When the new pump.was installed I thoroughly cleaned the surface it mates to. When installing the new oring on the pump itself I did not use any lubrication but when inserting the pump into the block I used coolant on the oring for lubrication. Maybe I should have used some sort of grease instead? Or maybe I also needed to use a lubricant when installing the oring on the pump itself?

The new pump was definitely torqued down to spec (4.7 ft lbs). I am very confident the leak is not coming from the top hose and is coming from withinn middle of the block just above that oil line, as I could see the seam gradually get darker from the fluid.

When changing the timing components + water pump I use this You Tube as a guide:


Something else to note when I order the water pump gasket it came with this:

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I could not figure out what this went to and therefore just did not use it. Is this something that should have been replaced somewhere along the way?

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Again thank you for all the help.
 
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