car history: 1997 civic lx sedan, 170k highway mi. recent coolant loss issue developed. new: thermostat, new green fluid, radator cap. i add to the radd 1-3 days to top off. bubbles in radd and??

 

cont.... overflow bottle overfills . no white smoke. blk gunk in bottle. radd is clean... hoses dry, radd dry, heater core

 

Blown head hasket? Any oil in overflow?

 

Any coolant leaks? Does it smell like coolant outside of the vehicle? Any white buildup on ur oil cap? The white buildup would signify coolant and oil mixing.

 

no white buildup. black goop on rad cap and in overflow bottle. smells like exaust when cap is off radiator!

 

Do bubbles appear constantly or every few seconds? It sounds like a crack on the block. Check the radiator compression. The coolant thats being lost is being burned. Smell the exhaust exiting the muffler. Should smell like coolant. The bubbles is compression being push into the cooling system. Radiator compression test is your best bet.

 

radiator cap off. engine running at opperate temp. rev 2 k fluid starts to bubble foamy like and let off. it then will flow w. no bubles.

 

I do a quick leak down on the motor too see if your loosing compression anywhere. Narrow down your problem to either the head gasket or some other loss in your coolant system.