So here's the saga of my overheating 2002 Honda Civic EX (at roughly 175000 miles)

Months ago, my car overheated once while going up a big hill, so it was recommended to me to replace the thermostat, which I did with a supposedly OEM part from Amazon. Didn't have any further issues until 2 weeks ago while on a road trip.

I had been driving all day, about 9 or 10 hours when my car started to overheat (dial went all the way to the H), so I pulled over and noticed coolant had sprayed everywhere. It was spritzed on the radiator hoses, the fan, and onto the engine parts around it. Looking at the overflow though, it had the correct amount of coolant, though the radiator itself was empty. I fortunately had some coolant, so I filled it up and managed to get to where I was going (wasn't too far at that point), though I stopped a couple times to check on it. Second time I checked it, I noticed the overflow was WAAAAY full, and the radiator was again empty.

At my destination, I took it to a mechanic who confirmed what I suspected: the radiator itself was leaking and needed to be replaced. So he did that as well as both hoses.

Hoping my troubles were over, I continued my roadtrip. I drove it maybe... 15 more hours when it overheated again, so I pulled over to check it out. Again, overflow looked good, radiator was empty. Again, I was almost to my destination, so I filled the radiator and got where I was going. Upon arrival I checked it again. Overflow was WAAAAY full, radiator low. Unfortunately it was a Sunday, and I needed it fixed immediately, so I had to take it to a Firestone, only place open. They did a "complete" cooling system check, and said the cap was failing completely and the thermostat was failing intermittently, so they replaced those things. I doubt it was OEM parts though. The cap looks different and cheap. I also extra made sure to ask them if there was a problem with the head gasket, which they said was fine.

One week later, I have been driving back and forth to work, no issues. But today I drove an hour, mostly highway speeds, and at my destination I noticed the overflow is AGAIN waaaaay too full, and now there is more coolant spritzed on the hoses, fan, and surrounding engine. Drove the hour back home and it didn't start to overheat till I was in the driveway.

I have no idea what could be causing this now, and I don't want to take it to a mechanic for them to say there is nothing wrong with it. Has anyone ever encountered this before? And is it bad to fill up the radiator with coolant when the overflow is SO full?

Any help is appreciated.

 

My 03 Ex was doing this for a while intermittently. My car has 117,000 miles on it and it would do the same. I recently had taken the cylinder head off to find out that the head was warped 0.003 in and so was the deck of engine block was warped as well. Chances are yours at 175k after being overheated is warped. I would have it checked out.

 

You likely have a blown headgasket. That's all there really is to it. Your next step would be to do a leakdown test to verify. My buddy's car had about 3% leakage on cylinders 1 and 4 (normal), then 10% leakage on cylinders 2 and 3. Cylinders 2 and 3 when pressurized would cause coolant to flow out of the radiator, which indicated a blown headgasket.

A blown headgasket is incredibly common on this generation of Civic. You should be looking into an engine swap, or paying to have the engine torn down and surfaces measured with a straight edge to see if a gasket could work, or buying a different car.

 

I had similar symptoms on my 02 Civic LX with 180,000 miles. I pulled the head, measured warpage. Shaving by a local machine shop was needed. The cylinder block was OK (within specifications). Reassembly using new OEM gasket set. The engine now runs at normal temp (past 8 months).