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Alright I’m gonna keep this as short as possible! I’ve owned a 2008 civic si coupe for almost 3 years now. Bought it used with 90k miles and now has 140k. Always runs smooth and always kept up with conventional oil changes. Car started over heating one day and drinking coolant. Had head gasket replaced and thought that would be the end of it.. few days after getting car back I’m back on the side of the road overheating.. cars drinking coolant and mixing with my oil even worse now.. took head off and checked gasket and it was fine. Sent head off to machine shop and they said it’s perfect. No warping or cracks. So at this point I’m thinking it’s a cracked block or my water pump passage is leaking.. car runs smooth and has a perfect idle. Just curious if anyone might know something I don’t? Hard to believe it could be my block? Look at these pics!
 

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Has anybody helped you with this I’m having the same issue I changed the water pump the housing gaskets and everything
 

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Alright I’m gonna keep this as short as possible! I’ve owned a 2008 civic si coupe for almost 3 years now. Bought it used with 90k miles and now has 140k. Always runs smooth and always kept up with conventional oil changes. Car started over heating one day and drinking coolant. Had head gasket replaced and thought that would be the end of it.. few days after getting car back I’m back on the side of the road overheating.. cars drinking coolant and mixing with my oil even worse now.. took head off and checked gasket and it was fine. Sent head off to machine shop and they said it’s perfect. No warping or cracks. So at this point I’m thinking it’s a cracked block or my water pump passage is leaking.. car runs smooth and has a perfect idle. Just curious if anyone might know something I don’t? Hard to believe it could be my block? Look at these pics!
Sad to see a k20z3 in this condition. I've never seen this problem before on this engine but I hope you find the solution. Nice rims tho!
 

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Alright I’m gonna keep this as short as possible! I’ve owned a 2008 civic si coupe for almost 3 years now. Bought it used with 90k miles and now has 140k. Always runs smooth and always kept up with conventional oil changes. Car started over heating one day and drinking coolant. Had head gasket replaced and thought that would be the end of it.. few days after getting car back I’m back on the side of the road overheating.. cars drinking coolant and mixing with my oil even worse now.. took head off and checked gasket and it was fine. Sent head off to machine shop and they said it’s perfect. No warping or cracks. So at this point I’m thinking it’s a cracked block or my water pump passage is leaking.. car runs smooth and has a perfect idle. Just curious if anyone might know something I don’t? Hard to believe it could be my block? Look at these pics!
I'm also having this problem. Head gasket has been replaced and I've sent it back three times to have the water passage resealed where the accessory mounting bracket meets the block. It still leaks from that same spot (externally from passage and drips down onto oil pan) and is also mixing with my oil! Brand new O-ring and rtv each time and I still have a leak and fluids mixing. Other than that, the car runs and idles fine so I don't think the block has a crack in it (though not impossible). I can see water bubbles on my oil dipstick and milky residue on my oil cap.

Did you ever figure out the root cause of your issue??
 

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It's more than likely a cracked block. I found the same issue on my '08 yesterday. View attachment 241966 View attachment 241967 View attachment 241968
I think this is my issue, too. I haven't taken it apart yet, but the previous mechanic claimed they inspected the water passage for cracks with a camera and didn't find any.

Did you have an external leak that appeared to be coming from that mounting assembly at all? The leak on mine leak from that area down the front of the oil pan, along with mixing in oil.

Where is the best place to find a long block? Short block or bare may be less $$$, though, if the head is OK. What are you (we) gonna do, man?!

I also started a fresh thread a few months ago when I joined, which didn't have any hits.

 

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I think this is my issue, too. I haven't taken it apart yet, but the previous mechanic claimed they inspected the water passage for cracks with a camera and didn't find any.

Did you have an external leak that appeared to be coming from that mounting assembly at all? The leak on mine leak from that area down the front of the oil pan, along with mixing in oil.

Where is the best place to find a long block? Short block or bare may be less $$$, though, if the head is OK. What are you (we) gonna do, man?!

I also started a fresh thread a few months ago when I joined, which didn't have any hits.

Yes, luckily It started to run down my oil pan in that exact spot. That’s the only way I would have found it.
 

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Yes, luckily It started to run down my oil pan in that exact spot. That’s the only way I would have found it.
So, with over 95% certainty that there's a crack in this block which will require motor replacement, I went ahead and installed some BlueDevil radiator and block sealer and topped off the radiator, after the 45 min idle time plus additional time to cool down. I would normally never use these types of products, but considering that the motor, or at minimum the block, will need to be replaced, I tried it as a last ditch effort. Also, did an oil change to empty out the never-to-be-mixed fluids. I've driven over 60 miles already (getting into vtec range a few times) and I cannot smell coolant anymore, haven't noticed the external leak, and haven't needed to refill the overflow reservoir at all; most importantly, no water bubbles or milky looking oil on the dipstick. I'm doubtful with how long this will last, though...

My options are:
1. Hopefully it will last long enough so I can trade it in on something. I currently have my home on the market and am looking at making a considerable profit, so I'm debating on trading it in with a decent down payment on a 2020 CTR.
2. Replace the motor and dump a bunch of money (boost, of course) into it making it fast and handle well.

Option 1 is out if the sealer doesn't last long enough for me to trade it in without someone noticing something with the block problem.

¯\(ツ)
 

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I was actually looking into block sealer this morning and thinking I really have nothing to loose. It looks like you made that decision for me, I’ll give it a shot. I was also considering blocking both of the PCV pathways in the cavity with the crack, grinding and repairing said crack with jb weld and adding a drain line to the cavity to vent coolant if and when the crack comes back.
I tried to do a dye pen inspection on the crack this week, but coolant slowly weeping from to spot caused poor penetration of the dye.you can actually see the coolant seeping into the developer in this picture.
241974
241975
 

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I was actually looking into block sealer this morning and thinking I really have nothing to loose. It looks like you made that decision for me, I’ll give it a shot. I was also considering blocking both of the PCV pathways in the cavity with the crack, grinding and repairing said crack with jb weld and adding a drain line to the cavity to vent coolant if and when the crack comes back.
I tried to do a dye pen inspection on the crack this week, but coolant slowly weeping from to spot caused poor penetration of the dye.you can actually see the coolant seeping into the developer in this picture. View attachment 241974 View attachment 241975
I wish I had the time and space to tear mine apart and explore other options. Good luck, man, hopefully the block sealer works for you, or the repair. I'll continue to monitor mine and let you know if that block sealer continues to work in my cracked k20. = /
 

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I wish I had the time and space to tear mine apart and explore other options. Good luck, man, hopefully the block sealer works for you, or the repair. I'll continue to monitor mine and let you know if that block sealer continues to work in my cracked k20. = /
I’ll keep you posted as well.
 

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150+ miles driven. No leaks yet. Driving her a little more aggressively (vtec) at times now, too.
At about 300 miles now and noticed it leaking externally again down the oil pan. I'm going to get it off the ground soon and take a look at that, but the radiator and reservoir are still full with coolant. Oil still looks good, no mixing. Gonna keep it going until trade-in time (hopefully). Hell, I'll put another bottle in if I need to!
 
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