Hello everyone, I am new on honda tech and I have an issue with my civic with a d15b dual vtec.
The issue is that I recently topped off my coolant by starting the car and taking off the radiator cap and filling coolant directly into it and also the coolant reservoir was empty I figured I would fill it later as I had just enough coolant to top off the radiator.
Went for a quick drive and came back, popped the hood and then the radiator cap and saw foam inside the radiator and upon giving it gas, it kept of coming not too much but enough to worry me, so the car has been running great no white smoke or anything of that sort, the engine oil is still good not milky,
Now I am left wondering why is it foaming and really hoping it is not a head gasket cause the car didn't overheat or anything like that and it is still original, never opened after assembly in factory where it was made,
Could anyone may be able to help me out?
Feel free to ask any questions.
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We'll first thing you need to do is properly fill and bleed the cooling system. There hundreds of videos on how to do this. Then you need to fill the reservoir to the full mark.

AFter that's all done.... if you have problems overflowing your reservoir you can start worrying about head gaskets.


​​​​​​Don't ever drive your car without coolant in the reservoir. The cooling system constantly breaths coolant in & out the entire time the engine is running. Each time the radiator fan comes on, the coolant system pressure goes negative and sucks coolant back in from the reservoir. Very important to keep all the air out of the system. If filled probably, it will naturally push minimal air bubbles out of the radiator cap and into the reservoir. Too much air in the system and the coolant will boil inside the engine instead of properly pressurize.