2005 Civic reservoir overflowing and it doesnt go back down the radiator after the engine cools down, i tried putting a new thermostat and a new radiator cap its still doing the same thing. i took it to a local shop and they told me a bad radiator or a blown headgasket, took it to honda dealership they did a pressure test and they told me i got air in the system or maybe a blown headgasket but the honda mechanic didnt say anything about a bad radiator now im confused.

 

Major problem with the head gasket is easy to spot, just start engine (cold) with the radiator cap off, rev it and look for coolant and air to blow out of the radiator. With a pressure tester, put it on, start at zero pressure, start engine and rev it and watch if pressure builds rapidly.

Bad radiator would lead to overheating, but no fluid imbalance issue until after overheating has occurred.

The only other thing that could cause coolant to fail to return to the radiator from the reservoir is an air leak in the hose between the two (or the seal in the top of the cap and the neck of the radiator). Operation depends on the slight vacuum that forms when the engine cools to draw the coolant back over.

 

Vehicle is running hot (Low on coolant) Perform pressure test (No visible issues found) Check fan operation (Both fans are working) Topped of coolant and bleed the system, ok at this time. Possible that the head gasket could be blown but at this time cannot confirm.

thats diagnostic report from the mechanic on honda said he didnt say anything about my radiator, could it be that the local shop is saying i got bad radiator so they can make fast money on me?

 

Bad head gasket..!!