Rep Power: 0

I have a friend with a 2004 Civic, LX I think. The coolant keeps running low, and I'm at a loss. I have replaced the lower radiator hose, and the thermostat and gasket. I can find no leakage in the engine bay, and the interior does not smell of coolant. I have pressure tested the system, and it holds pressure up to 20 PSI. Can anybody suggest what I'm missing? Thanks!

 
Rep Power: 224

Is the coolant reservoir gaining coolant and possibly overflowing? If so read the thread below, likely a bad head gasket.

https://www.civicforums.com/forums/3...reference.html

 
Rep Power: 0

Reservoir is not overflowing, and I forgot to mention I already did a combustion gas leak test, but that was a while ago; I should repeat it.

I also replaced the water pump.

Is a leaky reservoir hose a common culprit on these cars?

 
Rep Power: 367

have you done this test?

 
Rep Power: 224

But is it overfilled? If symptoms are not severe yet it won't overflow but will be slowly gaining coolant.

Not really. If it were leaking you'd see remnants somewhere.

Do this. These engines often pass a combustion gas leak test.

 
Rep Power: 0

Thanks guys, you were right. Despite passing a combustion gas leak test and a 20PSI coolant system test, the head gasket is bad. I did a leakdown test, and cylinder 3 is pushing coolant. Bummer.

Oh yeah, and it turns out the reservoir is overflowing. Hard to get accurate information from the car's owner sometimes.

 
Rep Power: 367

next step: (image courtesy of our sage ezone)

 
Rep Power: 224

Thanks for updating the thread

We always recommend using a Honda genuine head gasket or you may have issues reappear sooner than you'd like. Also, get the head checked for warpage and get it milled if necessary.

 
Rep Power: 367

and there were some issues with the tensioner, so be sure to install it properly