Rep Power: 0

I changed the thermostat in March and out of nowhere the heat does not come out of the vents until the thermostat opens. The bypass doesn’t provide heat out of the vents. I checked the overflow tank and the level looks good, the thermostat is new and I suppose that could fail, but is there a sensor that allows the bypass heat to work?

I did replace a sensor at the thermostat after an engine code earlier this summer.

Suggestions please.

 
Rep Power: 0

I just checked the cold engine and saw that the upper and lower hoses are collapsed like there is a vacuum in the system and the overflow tank is very full.

I removed the radiator cap but that didn't relieve the vacuum. There was no water showing at the top of the radiator, as expected. Would this be a blockage at the base of the overflow tank?

 
Rep Power: 125

This is almost certainly a failed head gasket.

 
Rep Power: 367

https://www.civicforums.com/forums/3...reference.html

 
Rep Power: 0

Not the news I wanted to hear.

The issue started a few days ago. I was hoping the overflow tank hose was blocked and the coolant couldn’t return to the radiator cap when the engine cooled.

About 6 months ago, I changed fluid and used a device from NAPA that attaches to the radiator cap and ran the engine quite a while until the bubbles stopped coming out. Isn’t this supposed to be the same a raising the front end of the vehicle?

I changed the timing belt and all the other stuff under the cover about the same time.

 
Rep Power: 0

Great link. I read everything to the end.

 
Rep Power: 0

Long story short….I checked the overflow cap for gunk combustion products….none….checked the radiator cap and none, but I noticed a tear in the smaller rubber gasket that seals the tank. So, the bad seal didn’t allow enough pressure to circulate water to the core until the tstat opened.

Large hoses, top and bottom remained cold. So, I took the time to elevate the front end, inserted the NAPA tool to bleed bubbles and there was almost no air in the system to burp out, but I did anyway. No small bubbles by goosing the engine either. Honda has to order my cap, but I’m sure that was the issue.

Very close mimic to a head gasket issue. Thanks to the link sdaidoji posted, I learned alot.