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Guest Message by DevFuse

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EJ25 block is plugged with calcium – should I bother cleaning it?

ej25 calcium block wtf

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#1 Dake



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  • Jefferson City, Missouri

Posted 13 February 2018 - 05:06 PM

I’m a car nerd and a hobbyist mechanic learning by getting my hands dirty. I picked up a 2003 Forester, Pacifica Blue with ~170k, bone stock, a great body and interior, and one big issue – overheating.


After pulling the engine I found that some of the coolant passages were plugged solid. Mystery solved. It’s a bit crude but the attached picture features a flathead screwdriver stuck into the calcification – that’s how dense it is. I have to assume the smaller internal passages are just as bad, though the water pump itself was clean and the passenger's side passages aren't *as* bad.


I was told phosphoric acid cleaner would eat away at it, but would it really get it all? I know the most effective way would be to pull everything and have the block hot tanked. I’m worried I’ll jump into a money pit of pistons / rings / bearings if I go that route. The engine ran well, and I can still see factory crosshatching on the cylinder walls. IMO they don't look bad but other people say they do. It might get headers and exhaust some day but it will most likely remain totally stock.


I have head / intake / exhaust / oil pan / valve cover gaskets, rear main seal, head bolts, thermostat, timing belt, water pump, and more waiting to go on.


I’m pondering my options before the heads go to the machine shop. Because of new circumstances I need this to be my daily driver, so I'm trying to save money. On the other hand, I want to do things properly and reliably the first time. Advice has ranged from “chip away what you can” to “buy a different block” ... what would you do?


High-res images here https://imgur.com/a/eGBDm

Edit: attached another image - is that oil weeping past the rings?

Attached Files

Edited by Dake, 13 February 2018 - 05:13 PM.

#2 golucky66


    Subaru Nut

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  • Barkhamsted Connecticut

Posted 13 February 2018 - 05:41 PM

First off. All that white stuff is from the Subaru OEM coolant conditioner.

I found this out the hard way on an 09 Subaru Outback that the shop I'm with was adding to the engine after coolant flushes (thinking it was supposed to go in that new of a car) and when I had to pull the heads to do the HGs, all that white build up was in there. Being as we were the only shop that ever touched this 1 owner car. It pointed to the coolant conditioner.


As for removal. Honestly, I didn't have a good way to get it out of the block. I ended up getting in with a chisel and slowly got it all out. Taking the cross-over pipe off to allow for flushing of the coolant passages with water. 

I tried brake cleaner, a few different forms of soap, and a few other products. Nothing took it off (at least not in a timely manner)


You might be best off just getting as much off as you can, replacing the water pump. And then dealing with the a restricted radiator or heater core when the time comes. 

There's not many small passages for coolant, besides the lines to the throttle body. 


IMO, you'll be fine with just getting as much off the block as possible. I didn't do anything about the head ports on the engine I was dealing with, besides the easily accessable spots. 

Also tagged with one or more of these keywords: ej25, calcium, block, wtf

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