Burping coolant from overflow tank.

[tonyn007]

Hello , what is causing this? My car never overheats, temp is fine. It doesn't matter is I fill the coolant tank or if I drive when its empty. After I park the car for awhile it burps coolant out of the overflow tank.

[Mike Brennan]

You have air in the system.
Google how to bleed or burp a cooling system.
You symptoms don’t suggest a head gasket, but check dip stick to make sure oil is clean.
i assume your anti freeze has good color as well.
I guess it is possible your cap is no good too.

[tonyn007]

Hello, Oil has recently been changed, tranny fluid recently change. New cap. Antifreeze color perfect. ??

[Digger]

Hello , what is causing this? My car never overheats, temp is fine. It doesn't matter is I fill the coolant tank or if I drive when its empty. After I park the car for awhile it burps coolant out of the overflow tank.

You're in a great place to have this kind of a problem this time of the year. Our winter weather will help you find the cause of this problem in one day.
Get a new cap for the coolant tank, the car is 14 years old and if it is the original, why waist time in the cold finding out you need a new one.
Cut the bottom off a gallon milk jug, then wrap the threads with some tape so it will sit on the expansion tank and not leak. There is a real tool for this, but an old milk jug will do.
Use the milk jug as a big funnel to pour your coolant through and a good seal will keep a good inch or two of coolant above the top of the tank while engine is running and not.
Fill the system with coolant with the car running with the heater on and let it run until temp gage reads warm, a little cardboard in front of the radiator helps speed the process.

After the engine is warm shut it down and let it sit with extra coolant in the jug above the tank and most of this week in an hour, two at the most the engine will be cold.
Syphon out the extra coolant down to the cold mark on the tank, get your jug out of the way and put the cap on.
Drive the car until gage reads warm and look to see if coolant level in tank is at the hot mark before you turn the car off.
After you've turned the car off watch the tank for about 15 minutes, if the radiator fan hasn't turned on and the tank hasn't overflowed, in this kind of weather it's not going to.
If the fan didn't turn on and the tank overflows while you are watching, restart the engine and turn the AC on to cold and make sure your cooling fan works.
Let the car get cold again and before you start the engine check the coolant level to make sure it's filled to the cold line, if low add some, if a little over leave it where it is for now.

If it didn't pop it's cork while you were watching and you have a puddle of coolant below the car where you parked, add some coolant and drive it till warm at night, then give it 20 or so minutes to cool down and use a not to bright flashlight to look for steam coming from a cracked tank or a pin hole leak.

Just an after thought here, a pinhole leak will suck air into the system without sucking coolant back in when the car cools down and with steam always coming out the tailpipe this time of year it's very hard to spot a tea kittling symptom of a suction side head gasket leak. So even if everything looks good when you finish, check your coolant level everytime you start and before you turn off the engine for the next week at least.

[avid0g]

"It doesn't matter if I fill the coolant tank or if I drive when it's empty." Oh No! Always keep coolant levels between the Cold and Hot marks! Especially when you have leaks!

The 9-5 reservoir bottle operates pressurised. It should not be capable of ever spilling coolant, and coolant levels should not be able to rise in it quickly. Anyway, liquid gushing up from the bottom is a sign that the system is not pressurized.

The cap may be leaking or not tight. The small hose may have cracks, or the small-hose-nipple may be cracked. Either leak would permit gas or steam to escape, so the system could not be pressurized. Another very common slow leak is the Heater Bypass Valve (located on the "firewall"). Later, as the system cools, air enters here.

If the antifreeze is diluted with too much water (more than 50%), the boiling point is reduced. This will allow excess pressure even when engine temperature is in the normal range. Then the pressure relief valve must open. Such a temperature may be reached just after the engine is shut off. You can solve this by purchasing a coolant tester. It can measure the coolant density. Add undiluted antifreeze if it reads low.

Another cause of leaking is when the pressure relief valve is out of calibration.

Another cause of problems is when the small hose is not carrying coolant to the bottle. If you cannot see some circulation through the bottle, then gasses cannot escape the engine.

Once the leak is fixed, you can adjust coolant levels correctly.

Once you fill the system with coolant, get any gas out of the passenger compartment Heater Core. The heater core needs be purged of air after the engine warms up. Turn up the cabin heat. When you can feel lots of heat, rev the engine briefly. You should hear the gurgling stop. Then you can trust the levels indicated on the reservoir bottle.