Coolant Overflow

exceptionaLS

exceptionaLS

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I parked my car in Manhattan today (34th and 10th) and went into the McDonalds. When I came out I had a long trail of coolant flowing away from the car. I looked underneath and saw that the drip was coming from the drivers side, almost directly under the coolant resovior. The thing is, and this has happened to me once before on this car, it doesnt leak coolant until I shut the car off. I replaced the coolant with some cheap stuff I bought up the street and drove home without another problem. Possibly filled the coolant too high? What do you guys think?

Oh yeah, It was approximately 35 degrees in Ny today.
 
If it was coming down behind the drivers side wheel, then the common problem is hairline cracks in the coolant reservoir (degas bottle). Normally the cracks are on the bottom of the tank, so you can't see them until you remove it.
 
There's got to be a hole or crack in there somewhere. You would have to overfill it a ton to get it to come out the top of the resevior I would think.
 
yeah but why would it only overflow when I stop? My friend said that when I stop moving air isnt going through the radiator so maybe the pressure builds up and the an emergency overflow valve opens. Does that make sense? Like I said, its only when I park after I drive for an hour or two. Come to think about it, both times this happened I was driving in stop and go city traffic so there was alot of time sitting at idle. Also I owned a beemer once and the same thing happened where I parked the car then came out and found a big puddle of coolant. What you think?
 
It's most likely happening while you're driving, you just don't notice until you stop. Ihad the same problem in the fall, and it was the coolant bottle.
 
Nope, it happens when you stop because the heat that is still in the engine doesn't have anywhere to go with no fresh cold coolant coming in to evacuate it. It builds pressure in the system and is then pushed out through the reservoir cap which is only rated to hold back a certain amount of pressure. It's either 14 or 16psi on these cars IIRC. If the pressure in the system gets over the caps rating it will vent and the coolant comes out kinda like when you shake up a soda bottle and then open it. The water in the coolant boils when the pressure drops which makes pockets of vapor that push the coolant up and out of the cap.

Usually when it starts to do that, that means its time to flush the system and put in some fresh coolant.
 
correct - it's 7psi. and on Gen1 the fan stops when the engine does - so the car get hotter then cools by air.......
 
Quik LS said:
correct - it's 7psi. and on Gen1 the fan stops when the engine does - so the car get hotter then cools by air.......
Click to expand...

Are you sure that's not 7 Kpa? (which would be about 16 PSI)
 
Yeah thanks guys. Now the only question is why is it over heating in the first place. I can't figure it out.
 
I had the same problem. Pektel & Quick are right.... the small cracks you most likely have in the degas (overflow) bottle can't handle the slight raise in temp when the engine is shut off. Replace the overflow & problem will likely disappear.
 
Antifreeze loses its ability to dissipate heat as it gets older. When it boils it creates air pockets in the cooling system, which will hold heat, and cause more boiling when the car is cut off. The best/first thing to do would be to flush the system to get all of the old coolant out. Then refill, and bleed the system of any air pockets. There's a writeup in the tech articles section on how to do it yourself.
 
haha ok.... but i mean there wasnt any coolant on the bottle after it all leaked out. The cap was dry, but there was a long stream of coolant coming from the car.
 
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