After replacing the radiator in my 1997 Civic (previous one developed a crack on the top, likely after I ran over a dead animal on the freeway), I am having a problem with the radiator cap steaming. Currently I am waiting for the car to cool down so I can take off the radiator cap and try bleeding the system as I don't know if I did a complete enough job (the coolant began overflowing from fill location, so I assumed that it was complete enough).

While it was steaming, the temperature gauge sat right in the middle like it usually does, and I did not notice the radiator fan turning on at any point in the 5-10 min period I had the car running, so I am unsure if the fan is working or not, but I did see the fan next to it turn on.

I have tried both radiator caps (the one that came with the new radiator, and the one off the old radiator), and both had the problem with steaming. Would not having the system bled properly cause the steam (but also not cause it to overheat)?

At this point, I am at a loss if it isn't the system being bled causing the issue, and I can only assume the radiator from AutoZone has some imperfection near the cap area causing it not to make a strong seal with the cap.

 

Start by replacing the thermostat and then bleeding the cooling system as described below.

If the fan never turns on even when the engine is hot, then unplug the plug for the fan switch on the thermostat housing and then short the two terminals of the free plug with a jumper wire. If the fan now runs continuously, then replace the fan switch.

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The bleed procedure may take 20-30 minutes:

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below

 

Are you saying it's steaming when the cap is on the radiator and the car is running?

If the cap is off and ur running the car for a while, steam will come out. Afterall that liquid is very hot. As RonJ said, the procedure may take 20-30mins. You only ran the car for 10mins. That may not be enough time for the thermostat to open and the fan to come on. My car takes a real long time before the fan kicks on.

 

Yea, my radiator fan takes so long to turn on that I didn't even think it worked. lol

 

Check the very top edge of the radiator neck for any dings or other imperfections. It should be sort of a round bead all the way around. There are two seal washers in the cap, one seals there and the other seals on the bottom seat further down. Also make sure the hose to the plastic tank is secure.

 

I left the car running for a while with cap off for a good while and it seemed to push out some coolant from the top (and I imagine some air as well). Placed cap back on and drove it around for a while, and I haven't noticed any steam since.

I don't know if there was too much fluid in the radiator and it couldn't push the coolant to the reservoir (don't think that is even possible), if there was air still trapped in the system, or if the cap just happened to start sealing properly, but it appears to be ok now. Thanks for the help, I just wish I knew what fixed this stupid issue...

 

Kinda hard to tell but it sounds like there just might have been some fluid left on the radiator and it was just steaming since it was hot. But either you wiped it dry or it dryed off itself.

Sounds like you did everything right. I would check the reservoir periodically just to make sure you have enough coolant in the system. Just don't fill it above the "high" line when it's cool.

 

Sounds to me like an air bubble was trapped in the system and you burped it out.