My daughters '96 Civic DX (115K) is having a coolant problem and I'm running out of DIY options.

I've installed a new radiator, after the first overheating episode, and a new thermostat. When the radiator and resevoir are full the car is fine, but when you turn it off the radiator overflows the reservoir. After doing this once or twice there isn't enough coolant left and the car will run hot when started.

I've thought about the water pump and I've read about "air locks" in the block or the waster pump not having a "prime". Is there a way to eliminate an air lock or to make sure the water pump is primed?

When I rev the engine with the rad cap off and the rad full, coolant will come out the top of the rad. I'm guessing that means there is circulation.

I've tried to guage if the water pump is working by squeezing the lower rad hose after the thermostat opens and reving the engine and other than it being hot I can easily stop any water from flowing through the hose. Is that normal?

A buddy at work wondered if the rad fan should be coming on after the car is off to keep the rad from getting too hot.

I'm going to check to see if the previous owner had the timing belt (and assuming the water pump) changed by removing the valve cover.

Any help is appreciated.

Thanks.

 

on the 88 there is a valve where the upper rad hose is attached to the engine. the person putting water in should open the vavle beforehand, and leave it open until water (antifreeze) comes out of it. then close it and fill the rest of the way. that prevents the air lock you are referring to .
is this a 4 or 6 cyl.

 

It is a 4 cyl. and it has a "sensor" on the thermostat housing.

This weekend I'm going to try any suggestions the forums posts for me (if I can).

Thanks.

 

If you think that there is air in the cooling system you can try and bleed it (which you should have done after you installed the radiator). On top of the thermost there should be a bleeder screw, once you loosen it coolant will come out. PUt the coolant in a cup or bucket. Close the bleeder valve after the coolant flows with no air bubbles. After the temperature of the engine goes above the middle line on the temp guage then the rad fan should turn on.x

 

Run the car at idle, with the radiator cap off..
let us know what you see in the radiator..

What happens when you shut it off, with the cap open..
If the coolant boils out after you turn the eigine off, it sounds to me like a crack in the block or head, creating a "hot spot" that boils the collant after the engine has stopped.





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Ford Model U History

 

When I run the car at idle with the cap off after the thermostat opens there is just coolant movement past the opening. If I rev. the motor the coolant jumps around and it looks like maybe a few bubbles might be in it. When it's really hot, the fan has come on a couple of times, it will froth when rev'd.

When I shut it off nothing happens.

A then again got it hot with the cap on and I noticed something that I didn't before. Coolant goes into the overflow when I rev. the motor. Maybe the rad cap is bad and the coolant level got low just by driving it.

I'll try another new cap, from Honda this time, and let you know what happens.

Thanks and cross your fingers.

 

Well it looks like it was the radiator cap.

The new cap from Honda looks almost identical to the new one I bought from O'Reily Auto Parts but upon closer examination it's a knock off.

The Honda had the "ND" stamped into the left wing and a little different words on the sticker. They both have red, white and black on the sticker and they are very similar. The knock off has a 3/16 or so hole up the center that allows the coolant to go straight through without any pressure at all. The Honda cap has a tiny hole in the same place but it doesn't allow air through it.

If I hadn't tried Chriskatana's suggestion with the cap off, I wouldn't have put it back on with the motor running and noticed the coolant going right out of the cap when I rev'd the moter.

Thanks for your help.

 

Hows it going??

My car isnt overheating or anything but i can hear my radiator cap hissing when i am done driving. think that this is it?

how much was the OEM cap?

 

I believe that lots of cars, especially as hot as it is, will send a little coolant into the overflow when you shut them down. It will then suck it back in when the engine cools.

Honda got $20.44 plus tx for the new radiator cap.