tremorfalcon

I have a 1987 Honda Civic 1500 12-Valve (so i think its CVCC) 5-speed manual transmission. Car was overheating so I took the thermostat out and boiled it in water and it opened. So i figured it wasn't that. Put it back in and it was still overheating. I put in a different 180 degree thermostat in it (that it had in the trunk when i bought it), and it was still overheating. So I put the 195 degree thermostat back in it. Then I took the waterpump off, it wasn't leaking and me and my father checked it and it spinned just like it should and everything, so I put that back in. The radiator is not blocked and the fan has been wired so its always on, so its not that. My father and I decied to take the thermostat out just to see what would happen. It didn't over heat. It didn't even get up to operating temperature (even with a grill block) after a while of driving. I figure it had to the thermostat and the boiling test i did wasn't a good test afterall. So I bought a new thermostat Stant 13879 195 degree Oe type thermostat. I put it in today and its overheating just like before. I bled the system of air. This makes no sense to me. I have no idea what it is, and with gas prices rising I'd really like to get this thing running.

The one thing I noticed is that the heater does not blow hot air most of the time its overheating. It may put out some occassionally but the majority of the time it will not put out hot air. When I had the thermostat out, it would put out warm air (noticably warmer than outside, but not hot because it wouldn't get up to operating temperature).

The other thing I noticed is that after it overheated and I'd park it in my driveway, I'd check the engine immediantly. The radiator cap wouldn't be letting out steam or anything but it was very hot to the touch. You could also hear the coolant hissing in the overflow tank. When I opened the bleeder screw it was basically steam that came out, not coolant. I stuck a wrench in front of it and its basically coolant in the form of steam.

I'll have to check the ignition timing too, but that wouldn't explain why it the heater wasn't putting out hot air would it?

Also this car does not have a muffler, (didnt have one when I bought it). It may be running lean, I don't know, however I figure this shouldnt cause it to overheat that much even if it was.

I changed the oil yesterday also, just incase for some weird reason (the 0.0001% chance) that the oil wasn't good enough or some horrible contaminant got into the oil that would destroy its lubricity. I put in 10W-40 Mobil 1 Synthetic High Mileage. Still overheating.

Those are the only clues I can give to this mystery. I have no idea what it could be. I've been trying to figure this out for months (due to the cold weather I haven't been able to get out much, thankfully its finally warmed up this month.)

Any assistance would really be appreciated.

Does anyone have any idea what it could be? Thanks so much for any help....

1992Si

Are the radiator fins still bonded the the tubes?

My 92Si had that issue. The fins became detached from the tubes.