Sons Civic overheating again, with loss of heat from the vents, after being fine since I put a bottle of flushing stuff through it a couple of weeks ago.
Got what I can only describe as thick soap suds type of stuff at the top of the rad when engine is running.
So presumably thats either residue of the flushing agent or head gasket failure.
Ime though HGF would be a stream of bubbles rather than something that looks like the inside of a washing machine before it starts the rinse cycle.

This started not long after the cambelt & waterpump were changed. Could be dodgy waterpump, but can a mechanical waterpump work intermittently ?

Had thought of throwing a new Rad on it to eliminate blocked fins, cool spots and the like, but I dont like playing parts darts.
Maybe a sniff test to check for exhaust gas in coolant ?