I have a 2003 honda civic. I recently replaced the timing belt and water pump. After a long weekend of wrenching, I forgot to bleed the cooling system properly. The next week I was on a road trip and the car overheated a few times. The overflow tank on the coolant was high (almost to the top), and when I checked the radiator it needed about a half to 3/4 gallon. I filled the radiator back up and didn’t have overheating problems until at the end of the road trip when I slowed down from highway speed to about 40mph. When I got home I replaced the thermostat (this time doing a better job of bleeding), and the next day I got misfire codes.
I took it in to my mechanic and he said he couldn’t see any head gasket leak after doing a couple of tests, changed the Electronic Load Detector and said call him if the check engine light came back on for misfires (all cylinders and random except for #1). It came back on and he recommended to change the upstream O2 sensor (which I had recently changed with Bosch brand) to a Denso brand.
The day after I changed the O2 sensor, the car started hesitating when driving, especially over 40mph, when the check engine light was blinking. Took the car to a different mechanic, who noticed the coolant was low and did another leak down test. He didn’t see and coolant in any of the cylinders, but after replacing the spark plugs he didn’t get any hesitation, but still got a misfire code and said the coolant was low again. So he put some stuff called AlumaSeal in the radiator and said that he thought it was a very small head gasket leak, and this should pretty much be a permanent solution, and that I should leave the stuff in the radiator and not flush it out.
I have a few questions:
- Does this sound like a good diagnosis/solution?
- Is alumaseal going to be able to fix this problem, or will it make any new problems? Has anyone used this stuff before with permanent results?
- Since the hesitation happened the day after changing the O2 sensor, could it be that I need to change the O2 sensor (again)?