So, I finally changed my head gasket yeasterday (I needed to change it because of some overheating problems - read here https://honda-tech.com/zerothread?id=826259.

Installation was easy and without any problems, no leaks etc. The OEM gasket looks more quality than my previous aftermarket one.

I have some questions:

1) When should I top coolant in the radiator - with engine cold or hot? With engine running or stop?

2) Should the cooling system be little pressurized while running or the hoses should be soft the same as with cold engine? If there should be pressure, what causes it? I assume that the cooland doesn't expand with temperature, right? Anyway, the pressure is not so high as with my old faulty head gasket (my hoses were hard like stone, now you can push it).

3) If I don't bleed all the air form the system, will the bubbles go out itself after some time?

Thank you,
Petr

 

1) Cold.

2) The coolant does expand a little with heat, that's why there is an overflow bottle.

3) Yes, they will, but by then you may have caused a hot spot where the air was sitting in the system, which is not good. Just fill it in the radiator until it comes out the bleeder valve, and watch it. When I rebuilt my motor last year, the coolant level in my overflow bottle actually dropped a bit the first couple miles I drove, but its fine now. I assume it was because the bleeder is slightly lower than the top of the radiator.