FL5 Coolant Reservoir Leak

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Just a PSA to rinse out a coolant expansion tank before installing, I think these are styrofoam fibers that worked their way in during shipping:

11th Gen Honda Civic FL5 Coolant Reservoir Leak IMG_8725
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evlsmurf

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Just to confirm, the Mishimoto expansion tank is the same for the FL5 that fits the FK8. Mishimoto could not confirm it fit, which is odd.
 

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I used a flashlight and mirror to see the coolant level reach the sight glass while pouring:

11th Gen Honda Civic FL5 Coolant Reservoir Leak IMG_8731
 

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Dang! I just hit 1000 miles. I wonder if there is anything that you can do before hand to prevent this from happening? I wonder if it's from vibration or just a crappy seam?
From what I understand, it's a manufacturer defect but who really knows. I had it replaced and am now at 6500 miles with no issues.
 

TW00Si

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So far the radium tank with hondabond is holding up. After one track day, no leaks.
 


TW00Si

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That thing will never fail. The hondabond you placed that day can never be undone. ?
Yeah I hope not. So far each time I check under the hood, no blue coloration on the hood or anywhere on/near the tank. I didn’t think I put too much but clearly I put too much when I had to scrape off from the inside. Thanks again for telling me to do that.
 

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Yeah I hope not. So far each time I check under the hood, no blue coloration on the hood or anywhere on/near the tank. I didn’t think I put too much but clearly I put too much when I had to scrape off from the inside. Thanks again for telling me to do that.
That is what we are here for my friend! And thank you for everything!
 

fenix-silver

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27Won. It’s a solid single piece, radium is two pieces and prone to leaking at the seal unless you use RTV sealant. 27Won is a big Honda vendor- I have their rear motor mount and it’s a perfectly machined piece.
yeah, 27won usually puts out some top-notch stuff. had their exhaust on my 10th gen Si and the build quality was superb
 


katch922

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Why not mishi? It’s a solid piece, I have no issues with mine. I wouldn’t go with radium, either mishimoto or 27won.
 

Doskiller

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Peeps seem to worry about the sight glass leaking. Here's a thought ........ just don't fill it up all the way to the sight glass in the first place if nervous ................ ;-)
 

evlsmurf

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Peeps seem to worry about the sight glass leaking. Here's a thought ........ just don't fill it up all the way to the sight glass in the first place if nervous ................ ;-)
Have there been issues with the glass leaking?
 

TW00Si

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Have there been issues with the glass leaking?
Not sure. Mine hasn’t. And it’s filled halfway. The threads comes pretreated. I have not seen any leaks so far. It was my concern with the radium tank. But seeing how you can use sealant on it, I was willing to take chance since I didn’t like the looks of the other options currently available.
 

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