Chodster

Hey I have a '94 hatchback civic that had a leaky radiator. i dropped a new one in today and drove it around the block and it seemed to be going well. I let it idle in my driveway for a bit and noticed a whistling which turned out to be the coolant literally boiling in the resevoir. The resevoir had a tiny pin size hole in it I noticed, but it was above the max fill line so I didn't know if that had anything to do with it. If anyone's got any suggestions I'm open to them. I don't know too much about cars, just that this shit ain't right. All help is appreciated.

p-stone

Did you bleed all the air out of the coolant after you installed the new radiator?

Fabrik8

Is the fan turning on? It's possible that the temp switch for the fan is not working, so you're not getting any forced air cooling while the car is sitting still. It's not an uncommon Honda problem. You should hear the fan kick on in a few minutes or less after it's warmed up going around the block, and then sits at idle standing still. Thats' the first thing to check.
Make sure it's bled too, yes. Pockets of air turn into high pressure pockets of steam..

Chodster

fan is working perfectly. as far as bleeding the air out...i have no idea what that means, so that could very well be the problem bc there's no way i did that if i don't know what it is. after i bleed the air out, is that pinhead-sized hole going to affect anything?

Fabrik8

You bleed the air at the highest point in the cooling system, wherever that happens to be on your car. If you've just filled the system with coolant from the radiator cap, any higher point in the system is going to have air trapped in it. You really shouldn't have fluid boiling in the overflow tank, I suspect that you have fluid or air getting pushed into the overflow tank from the radiator, which is pretty odd. That probably means there is a lot of air that is expanding and getting forced out into the overflow tank probably. CLICK HERE to start downloading the factory service manual for your car. It's 85MB so you've been warned. Then go to the coolant section and follow the bleeding instructions.

The more I think about it, the more it sounds like a faulty radiator cap, or the wrong cap for the car. Did you replace the cap, and if so, did you get a stock (OEM) replacement from a Honda dealer? I still think this is a problem with air in the system, but you shouldn't be seeing the strangeness with the overflow tank with just air in the system. You should be having overheating problems (or at least running a bit hotter than normal) with air in the system. Make sure the cap is seated properly (check with the engine cool) and see how much air there is in the radiator core when you take the cap off..

To speed you along, coolant system bleeding is page 185 of the pdf file.. You owe me...

Chodster

Looks like the problem was bleeding the air out of the radiator, i took p-stone's advice and just filled the radiator with coolant and let the car idle with the cap off until all the bubbles rose to the top and it drained out the resevoir. car's running fine again.

Fabrik8

Sounds like it's fixed, good..
You should still bleed out any residual air at the bleed bolt just in case.

cpakc1

I have seen a few D-series motors that didn't come with the bleed valves on the water neck. I always wondered if they required a different rad cap.

Fabrik8

The cap should run the same pressure for all D series I'd imagine, so it should be the same one..

caeavesRSX-S

Can I get in on this? I don't think my radiator fan is coming on at all. I let it idle forever and nothing. I checked the fuse and it is fine. I downloaded the service manual you provided (thanks!!) but what should I check first? I saw the tests for the fan motor, relay, fan switch, and thermostat. Which one is most common on a 92 civic dx with 178,000 miles on the beast.

Edit: Jumped fan motor and it came on! Good.