So pretty much my Honda civic from 05 has been having cooling issues and I've done some work on the vehicle in attempts to fix the issue; I've replaced the entire engine, replaced both the radiator and fans, leak tested the system and have gone through 3 thermostats none of which have stuck.

Though every time right before the engine begins to overheat the overflow reservoir coolant seems to have lightly spray out, I have never witnessed this actually happen but when I do pop the hood after the gauge seems higher than usual there is drops of coolant on the fan and the engine. There also seems to be the smell of coolant before the overheating occurs in some occasions, my current belief is the Nevada heat is the cause of the issue and the radiator and fans aren't enough and does not give my engine enough coolant; In result of this belief I cut the spring of the thermostat and had it set to an open position thus to increase flow of coolant but even with that the engine continued to overheat.

I'm legitimately stumped and various mechanics have also been confused on the situation, I'm considering taking the car to an Official Honda service center but before I do so I'm trying to get some help with this before having to pay an arm and a leg for service costs.

additionally, the fans still spin at the correct intervals, recently air tested the cooling system, and all hoses don't seem to be damaged in anyway as for the overflow tank the water seems to be all the way at the top and boiling during these overheating issues.

  • 2
    Welcome to Motor Vehicle Maintenance & Repair! Two things: 1) did you use OEM thermostats? For some reason, aftermarket stats don't seem to work very well in these engines. 2) What about the radiator cap? You don't mention it, but if it's not holding pressure, you're going to get overheating issues. I used to own an '03 Civic with the same engine as in your '05. These are troublesome engines. You said you replaced the entire engine ... with what? I replaced the one in my '03 with a JDM engine and it worked out fine. These engines are known to have head gasket issues ... Jul 13, 2022 at 10:42
  • ... mainly due to people using non-Honda coolant in them. The headgaskets will start leaking because regular (ie: green) coolant eats the head gaskets over time and you get compression leaking out into the coolant system and coolant leaking into the cylinder. If you bought a replacement engine from here in the States and the "someone" who owned it before you didn't do the proper maintenance, you could have swapped in the same problem you just got rid of. Jul 13, 2022 at 10:44
  • @Paulster2 Sorry should have told you the swaps, basically the swap was the same honda DX engine that the mechanic who was doing the job for me bought for that reason, and I know for sure it was swapped since when I came to pick the car up after it was ready I saw the old engine he even marked all the faults that caused it to break. As for the cap I'll buy a new one and replace it see if that helps, and if not that I suppose its a head gasket issue since the coolant I put in my car is of course green and or the yellow which I was told is the universal type of coolant. Jul 13, 2022 at 15:17
  • @Pᴀᴜʟsᴛᴇʀ2 thanks a bunch for letting me know the possible issues, I'll post updates after I swap the cap, one more thing to note the car only seems to overheat after a long drive (abt 20-30 minutes) and during the middle of the day when the heat here is at its peak the last time it was getting hot it was about 110 outside. Never ran into a cooling issue in the mornings (6-11 am) or night (6-12am) though this might be because I don't drive it for long since its a point A to point B car as my first vehicle. Jul 13, 2022 at 15:21
  • One of the things I did in my '03 was to ENSURE every morning the radiator was completely filled. If I didn't, it would overheat. By overheat I mean, the temp needle would suddenly peg and then start wildly fluctuating. To fix it, I took the head off and was ready to replace the head gasket, but discovered that the camshaft was showing a lot of wear. The cost of a JDM engine was actually cheaper than replacing the cam and valvetrain, so I went that route. BTW, only the EX & CNG versions have different engines in them (at least in the States - as long as my memory hasn't failed me). Jul 13, 2022 at 18:05

1 Answer 1


I've gone through 4 radiators 2 thermostats and 2 water pumps to find out that Hondas take a special antifreeze called type 2 made by Honda. Since using that, no more over heating problems.

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