weaponsgrade

I have a 95 Honda Civic Ex. I recently replaced the radiator:

https://honda-tech.com/search.php?searchid=5820124

The engine seems to be running very hot, though no warning indicator lights have come on . . . yet. The needle on the temperature gauge climbs to the red zone and will stay at or near the red zone. The needle will drop a bit, but then climbs back into the red zone.

Any ideas? I'm thinking it might be a faulty thermostat that's not opening at the correct temperature, but is instead opening at a much higher temperature. This would seem to explain why the needle drops a bit. I didn't bother changing the thermostat when I replaced the radiator.

I don't see any evidence of coolant in the oil and there doesn't seem to be any drop in the oil level. However, I've noticed some white gel like substance on the bottom of my radiator cap. Heater seems to be working fine.

Some other background information. I added some headgasket sealant in with my coolant when I did the radiator replacement. It was more of a preventative measure.

Doc13

Let's just say that gooey stuff is the sealant.(fingers crossed)

Now, I'm thinking it could be the thermostat is stuck closed, or your water pump has malfunctioned.

Whatever it is, you shouldn't drive with the temp sensor showing in the RED.
You're asking for a headgasket issue.

Do you have heat inside the car?

300whpej

have you checked/changed your hoses? thermostat might be sticky, but it sounds like your blowing your head gasket and that your motor is soon to follow if you keep driving it while overheating. easiest thing to do is going to be to change your head gasket, thermostat and hoses.

what is head gasket sealant?

weaponsgrade

I have heat inside the car. The only hose I changed was the lower radiator hose. I've since stopped driving the car. The head gasket sealant is this stuff you can add to your coolant that's supposed to seal any gasket leaks. I don't recall the exact brand I bought, but I can find out tonight. The water pump was replaced about 65k miles ago.

wmac

how does that stuff know it isn't sealing off coolant passages, or cloggin vanes in the radiator?
i would never use that kind of crap.
if a gasket is leaking, replace it.
don't buy 'magic beans' and expect it to work.

weaponsgrade

Update: Drained the coolant (and sealant), replaced the radiator since I could see some of that sealant inside, replaced the thermostat, and backflushed w/ a garden hose to get as much sealant out as I could. I've driven about 200 miles so far and during that time the car was running fine. But now, I have a different problem (see new thread).

Koopa Troopa

Did you bleed the coolant after changing the radiator and adding more coolant?

weaponsgrade

yes