Okay, my car doesn't appear to be leaking or burning up coolant. Also no signs of overheating according to the temp gauge. My problem is the coolant going to the overflow resevoir does NOT flow back to the radiator as the car cools. So every week or so, I have to open the radiator cap and manually take the coolant from the resevoir and pour it back into the radiator.

I suspected it the was the radiator cap so I replaced it with a OEM Honda one, same problem.

Its starting to get annoying, what else could be causing this problem? What should I check into?

 

Something breaks the suction in that hose over to the reservoir. Ever try to drink thru a straw with a hole in it? Cracks in the hose? Cracks in the little plastic elbow in the reservoir cap? Missing the hose going from the reservoir cap down to the bottom of the reservoir?

The radiator cap has 3 seals. The smallest one just seals against itself, & pulls open when the radiator wants to suck water back in from the reservoir. If that doesn't open you get collapsed hoses instead of air in the radiator.

The 2nd seal is the one that lifts when you get over-pressure. It seals against a rim down inside the radiator neck. Sounds like that one is OK.

The biggest seal in the cap, seals against the very top of the radiator neck. If that ridge around the top of the radiator neck has scratches or gouges in it, it'll suck air in thru there, instead of sucking coolant in from the reservoir.

 

I'll definitely investigate the areas mentioned. thanks. Additional comments or suggestions are still welcomed.