Rep Power: 0

So I just got this 05 Civic EX 5MT. The coolant reservoir fills up to the top by itself and the heater does not stay hy. I'm leaning towards replacing the radiator to see if that fixes the cooling/heating problem. I replaced the thermostat with a failsafe thermostat and the temp gauge is always closer to the cool side of the temp gauge. The reservoir fills up by itself and blows coolant out from the top which makes a mess. Thanks for any help. I'm about ready to get rid of this car if I can't get it to work right.

 
Rep Power: 126

Head gasket

 
Rep Power: 225

Unfortunately, he is likely correct. Here is a thread with some more info. This is an extremely common 7th gen issue.

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

You'll almost certainly find the radiator coolant level low. Fill it up and drain the reservoir to the proper level. Bleed the coolant system by getting the front up high and letting the engine run with the radiator cap off, heat of full. If the head gasket is bad you will see a constant stream of bubbles coming out of the radiator. There are also a couple other test methods in that thread, definitely read it.

 
Rep Power: 134

Dang man, looks like this car needs a head gasket and clutch repair...

 
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I know. It runs surprisingly well though. If I don't slip the clutch it grabs and goes no problem.

So I got the front end up and bled the radiator and there was not a constant or semi constant flow of air bubbles coming out. My rad does look a little beat up so I'm going to replace that as I can get it for about 40 bucks.

 
Rep Power: 368

this one spells headgasket, denial will not help you. Don't waste money buying a radiator.

Test it.

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

 
Rep Power: 100

Based on this info, I would be about 99% certain the thermostat is STUCK OPEN. This would cause the engine temp to stay low and the heat to be lukewarm only.

The Failsafe thermostats are designed to stick open and stay open to protect the engine from overheating. Unfortunately, they tend to fail long before an overheating condition occurs and then they are stuck open for good. Crappy design. I know from experience...I went through two of them and BOTH failed open within a couple weeks of installing them.

SOLUTION
Get rid of the Failsafe thermostat and get a Stant or Gates brand. Napa and AAP typically sell Stant, while Rock Auto will sell both. Once you've done that, then see if you have problems and go from there.

 
Rep Power: 0

I have same issue, however every coolant part has been changed other than the fan itself and a heater core. I can drive car around all day without it overheating but as soon as i put some jam into it or go up a large enough hill the temp starts going up and i lose my heat. Plugs are dry , coolant level is fine ( until it overheats and boils over ) , no white smoke, compression is fine, hydorcarbon test passed. No oil/coolant mix. When the temp goes to H like full are the fans not supposed to stay on until it reaches min spec?

 
Rep Power: 368

Don't ask first. Start by reading.
couple posts above yours

 
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I have the exact same issue. I replaced my failed thermostat with a Failsafe. I’m assuming this is the train of events that followed. My head gasket went bad (300k miles lol), and that caused overheating which prolly locked my thermostat open. I wasn’t sure so I replaced radiator. No help. Still overheated randomly and spewed out overfill. Replaced reservoir and bled system of air. It’s eradicated now for the time. Drove it hard then let it sit for 30 min. No issues. Will try new regular thermostat, and if it comes back i have a newly serviced engine ready to drop in.

 
Rep Power: 368

the test on the video is easy. just do it and confirm if gasket or not.
If it does not pass, save money to do gasket.

 
Rep Power: 0

dude you’re right. It’s gotta be head gasket. That would force air into the cooling system and fill the overfill reservoir and cause the air pockets which spike the temp and no heat through heater core. Thanks man