Coolant Leaking From Under Coolant Cap

JMRICKER

MEMBER
1998 CHEVROLET CAVALIER
4 CYL

A week or so ago, I back the car out of the garage and had it idling when I noticed a puddle of coolant on the ground. I looked around under the hood but didn't find anything other than some coolant on fill reservoir. I cleaned it up and checked again and noticed a small stream running from under the cap.

My thought then that maybe the cap was bad so I went to autozone and got a new one. The next day I checked the fluid levels, filled it, drove to my destination, then checked it. This time I had steam coming from under the cap and a good amount of coolant coming from under the cap.

My next thought is maybe something is wrong with the tank, however, I was also wondering if maybe the coolant is getting hot because of something else, and the steam I was seeing is actually the cap doing its job. So then I'm thinking of changing the thermostat.

So my question is this: Should I change the thermostat, the fill tank, or could there be another source of trouble?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Is the engine running at a normal operating temp? Have you checked the tank closely to make sure there isn't a crack in it?

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Tuesday, December 7th, 2010 AT 1:32 PM

JMRICKER

MEMBER
3 POSTS

My car has a temp guage that reads 0, then there is a notch for 195, then a notch for red. My car normally runs a tick under the 195 mark.

When I drive, after about 30 minutes the needle will rise to a tick above the 195 mark.

I'm going to check closely like you asked so what I did this morning since I had a little time is I disconnected the tank from the chasis so I could set it up to the side a little bit, topped off the coolant (it was probably only half full), and wiped the tank down really good and underneath the tank. With the tank set to the side like it is, I should be able to see all around it if a leak appears. Tonight when I get home, I'll run the car and idle it until I can see some sort of action or the temperature begins to rise whichever comes first. I'll let you know what I find.

Thanks!

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Tuesday, December 7th, 2010 AT 2:38 PM

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Let me know. A good thing is that the vehicle runs at a good temp. It is where it should be.

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Tuesday, December 7th, 2010 AT 5:04 PM

JMRICKER

MEMBER
3 POSTS

I was able to run it a little while ago and I think I know whats going on but its not good. I ran it for a few minutes and soon saw drops of water coming out of the exaust pipe. I called my father-in-law about it and he thinks that I did blow a head gasket which is what I was leaning towards as well. Its not alot of water, it just sort of spits a drop or so but after a minute or so puddle formed.

When the car got up to normal temperature, fluid did start to leak from under the cap. I'm thinking compression from the engine is pushing the water out through the cap.

Are you familiar with this particular engine configuration? I'm wondering how difficult it would be to do this myself.

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Wednesday, December 8th, 2010 AT 7:55 PM

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Before jumping to conclusions, it is normal for water to condensate in the exhaust system and come out as water when the system begins to heat up. If you had coolant coming out, the exhaust would be white all the time because it would be burning coolant. When the engine is cold, open the radiator cap and see if coolant is forced out. Also, check the engine oil to see if there is any evidence of coolant getting into the engine oil. As far as the engine, I can help you out with that. Just let me know what size 4 cyl it is.

Let me know everything you find. If the leak stops, you may just need a thermostat. There are things that make me think a head gasket, but then others that don't. Just make sure the overflow resivour isn't cracked. I know you already looked, but check again.

Let me know what you find. Before removing the head, I will have you do a compression test to see if any of the cylenders are low on compression indicating a headgasket problem.

Joe