RustyShackle

Well I think the inevitable finally surfaced right as I clicked over to 150k km.

Had trouble getting good heat at idle last week so I checked coolant and when I took the rad cap off there was a big hiss/gurgle and saw low coolant in the rad. Coolant reservoir was slightly over the max line.

Went to get some prediluted honda/acura coolant and topped off with heater running squeezing the top hose getting the bubbles out. I probably added 300-400 mL until I didn't get anymore air bubbles.

Checked it today saw the reservoir is nearly overflowing and radiator is low again. I do not drive much rarely more than 10 minute trips to work and around this small city. I probably initially added a little too much as the reservoir was slightly over max when I filled the radiator.

I have in the last 3 years previously replaced: the rad cap because overflow was getting high in the hot summer, air/fuel sensor, type 2 coolant, timing belt and water pump at Honda, input shaft bearing at Honda.

I'm thinking replace the radiator cap with an OEM honda cap, get the coolant to the correct level in the reservoir/rad and monitor the coolant daily. Maybe also have the cooling system pressure tested to rule that out? I see no visible ground leaks.

I am 100% expecting this to be a head gasket but any suggestions/comments are much appreciated.

ezone

With the radiator completely full and system burped, and the radiator cap installed, squeeze hard on the top rad hose and determine if it feels like you put pressure on the system by squeezing it.

If the cap didn't seal, you'd easily collapse the hose as the system wouldn't be able to contain pressure---same as if you were to squeeze the hose while the radiator cap was off....

Cap seals ok? Good.

After you drive it and discover the overflow bottle has filled to the top or belched out again, squeeze the top hose and see if the system has pressure in it (if the hose collapses when you squeeze that would mean the system pressure cap can't contain 13-15 PSI)

Now leave the engine running and take the overflow cap off and watch if there's a continuous slow stream of bubbles coming up that never ends.

The never ending slow stream of bubbles would be a primary indicator of combustion gases entering the cooling system (head gasket breach). More tests can be done to confirm if you want to

Find the overheating common causes sticky thread in this forum, read the very first post in it, watch the two videos as well.