2005 Honda Civic Overheating – 4 shops can’t fix

Hello,
I’ve been having some chronic overheating problems, have made numerous repairs and have taken the car to 4 mechanics and no one can figure out why my car continues to overheat. Please help! Sorry for long post, I wanted to be as thorough as possible and explain everything.

2005 Honda Civic SE
4 Cylynder – 1.7 L
Manual Transmission
146,700 miles
US Car

Before posting, I went through ETCG guide on overheating and am still unsure or could use some guidance. Also, I had hoped that taking the car to multiple shops would find a solution. I just can’t afford to keep taking it to shops and get no more answers.

I bought the car 2 months ago. The person told me that car overheated on longer trips but did fine with city driving. Before I bought it I had it checked by mechanic and told him of problem. They said radiator cap was faulty. And replaced. They also said fuel mixture sensor was bad (error code P0135), and that should be replaced at some time but shouldn’t cause overheating problems.

I went on a trip and drove 500 miles with no problems. I’m from the South and went way North and didn’t expect the temps to get so cold at night. We’ll the previous owner must have put too much water in radiator when last overheating occurred and it cracked my radiator.

I had new radiator put in. They also changed thermostat. On way back, I drove 250 miles with no problems. Pulled over and got gas, started car and temp immediately skyrocketed. Before I even left the station. I didn’t drive anymore. Got hotel. Read online and burped system. Lot’s of air. Drove another 250 miles with no problems, until getting off interstate and temp climbed very quickly and maxed out. Immediately pulled over.

Took to mechanic. They did pressure test on system for leaks. None. Did cylinder leak down test. Fine. Did Engine Block test: Fine.
I went ahead and had them put in new water pump and timing belt because the car was well past due for one.

Still overheats after driving for 40 minutes on highway or so and then intermittent city driving. I’ve found that I have to open radiator cap, top off with fluid. I’ts always low, like may 10-12 ounces or so,(But expansion tank usually always has more than enough fluid in it) let it run with heat on for 10 minutes, let air bubbles out and then I can drive for days in the city with no problems.

When it overheats, it looks like fluid is sprayed a foot in diameter all in engine compartment. I don’t have a cap on expansion tank. It’s the type that has threads on it. The mechanic said it’s not critical to have one. Is that true? And they said it wouldn’t be related to problem. So I haven’t bought one yet. It almost appears that the antifreeze is coming from expansion tank when it overheats. But not sure.

• I’ve always immediately pulled over and turned off car when gauge got hot.
• I’ve tested my fans by directly wiring them to power. Fine
• Although, when it overheated I opened hood, kept running just for a second, and noticed that fans were NOT on. Shops say fans are fine though. And I do see them running sometimes.
• There is no white smoke, no milky oil
• Had thermostat replaced twice!
• It appears I’m loosing coolant somewhere. I see a drip if left overnight, but don’t know where.
• Hoses have not been replaced.
• When it “overheats” it is maxed on temp gauge. But it has NEVER actually had steam coming from engine.
• No shop has actually been able to get it to overheat. So no temp stats. But upper hose is very hot and hotter than lower. Upper hose is firm when overheats.
• The heat usually completely goes out when it overheats.
• The heat works fine, very hot when driving. Almost too hot.
• If just left idle after cold start, heat takes 10+ minutes to come on.
• It doesn’t seem as if the expansion tank coolant is moving into radiator, not sure how to check this.
• The expansion tank full level line is so hard to see and so far down in the engine compartment, that I can’t tell if it has fluid. It’s always had enough in it. And usually too much. I’ve poured too much in now and it’s a couple inches from top.

The shops I’ve taken it to say they have burped it and left if running for over an hour.

I’m getting so frustrated. Reddit says it’s a HG. But 2 shops say it’s not. I don’t want to spend a couple thousand on HG unless I know it’s a HG for sure. I know Honda’s with this engine are notorious for HG problems. But tests don’t confirm that’s what is happening.

I saw a similar thread and it ended up being the hose that goes from radiator to expansion tank had collapsed causing air to enter system. I don’t know how to check something similar. Seems maybe coincidental if I notice that expansion tank and radiator may not be sharing fluids? Again, everytime after it “overheats” when I open radiator cap, I can’t see fluid inside radiator. It takes 10+ ounces to reach the neck of radiator.

My guess is that air is coming in somehow causing to overheat and since i don’t have an expansion tank cap it’s causing the antifreeze to pour out in to compartment.

Regardless, after radiator froze and broke. Overheating became regular. Maybe they didn’t put it back together right. Or it’s a faulty radiator. Or the freezing damaged the engine. But multiple shops have tested for this and found no evidence.

Or could it be something else? Transmission, clogged radiator, exhaust, catalytic converter, heater core, fan thermoswitch, or ECTS?

Really appreciate any help.
Thanks!