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Old 06-30-2022, 09:33 PM   #1
redrexmeister
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Default Possible head gasket issue

I had the car lose coolant and briefly overheat due to radiator leak (2008 STI). I replaced the radiator (installed Megan Racing aluminum rad), and charged fresh coolant. The car seems to run fine. However, I see bubbles in the white coolant overflow tank. The coolant in the white tank keeps rising.

I did combustion gas leak test of the coolant . The blue fluid in the test tube turned to yellow. I did the test twice, using the test tube inserted in the radiator neck and the other time with test tube in the upper expansion tank. In both cases within a minute I observed yellow color.

Thus, it appears I have a leaking head gasket or possible crack in the head or block.

Is the combustion gas leak test fairly accurate? I mean, should I be checking for anything else before tearing apart the engine?
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Old 07-02-2022, 02:04 PM   #2
Elbert Bass
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That is a pretty conclusive test. The fluid changes color in response to carbon dioxide. The ONLY way CO2 can get in the cooling system is from the combustion chamber.
Not really anything left but pull the heads, inspect the head gasket for the point of failure and measure the deck and head for flatness.
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Old 07-03-2022, 03:17 AM   #3
mnuckolls
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Yes, that fluid changing color is very accurate. Especially considering it overheated, most likely the head gasket failed, which is pretty common. When I worked for a Subaru dealership, I was doing a least 1-2 set of head gaskets every week. so, pull em, send the heads to be cleaned at a machine shop, and replace the gaskets, timing belt, etc.
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Old 07-03-2022, 12:37 PM   #4
Elbert Bass
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Quote:
Originally Posted by mnuckolls View Post
Yes, that fluid changing color is very accurate. Especially considering it overheated, most likely the head gasket failed, which is pretty common. When I worked for a Subaru dealership, I was doing a least 1-2 set of head gaskets every week. so, pull em, send the heads to be cleaned at a machine shop, and replace the gaskets, timing belt, etc.
Yep, EVERY tech in the shop got at least one EJ head gasket a week. I quit three years ago after that gravy morphed into 3 warranty oil consumption short blocks or valve spring replacements on FB/FA engines.

Here's my favorite - a tech replaced a short block in a STI - left a head bolt loose. By the time it got to me you could fill the cooling system and watch water and fire shoot out the front of the engine next to the water pump. Zoom next to the exhaust valve on the head...

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Old 07-07-2022, 06:46 AM   #5
redrexmeister
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Wow, that is quite a story. You just don't know if you want to cry or laugh.

If the short block is out, should I change the piston rings?

If for some reason the short block is a problem (I know it's unlikely but just want to consider this scenario), would it be possible to use 08 STI heads with RA short block?

The money difference between between 08 short block and RA is minimal, it seems like RA block is a bit more sturdy?

OEM gaskets or aftermarket?
Are the bolts re-usable?
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Old 07-07-2022, 06:46 AM   #6
redrexmeister
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Wow, that is quite a story. You just don't know if you want to cry or laugh.

If the short block is out, should I change the piston rings?

If for some reason the short block is a problem (I know it's unlikely but just want to consider this scenario), would it be possible to use 08 STI heads with RA short block?

The money difference between between 08 short block and RA is minimal, it seems like RA block is a bit more sturdy?

OEM gaskets or aftermarket?
Are the bolts re-usable?
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