Yet, another problem, this time with the cooling system

[Hundred]

Alright, yet another problem has rose up, bringing the count to #10 in the past 2 months.

Sometimes when I get home from school, the coolant reserve tank is almost filled to the top with coolant. I hear a "gurgling" sound from the radiator hose area.

Now, the coolant in the tank is not boiling, that has happened before and eventually all the coolant in the tank blew out and the car overheated.

This time, the car is not overheating, the coolant is filling the tank to about 75% of it's capacity. The dummy needle is staying at half. Once the coolant goes back down, I start the car up and it's fine. This has happened twice in a months worth of driving.

I have already bled the system and replaced the thermostat. I am thinking maybe there is to much coolant in the system? The radiator and cap were replaced about 2 years ago.

My next step is to drain the system, inspect the hoses and fill it back up again.

Any help/suggestions would be wonderful.

 

[CheeseHelmet]

It's completely normal for the level in the overflow tank to rise after driving the car, that's why you're only supposed to fill it halfway. As long as it's not overflowing I'd say you're fine, you can replace the radiator cap if you're really worried.

 

[pw~mp5]

Symptoms sound like a sticky thermostat, but I see you have already replaced the thermostat. There could be some other blockage. Have you flushed the cooling system? I like to use distilled white vinegar. Then refill the system 25/75 antifreeze to distilled or deionized water and add a bottle of Water Wetter (or a similar product). You may want a different coolant ratio depending on the weather where you live, but generally less antifreeze cools better.

 

[Hundred]

It's completely normal for the level in the overflow tank to rise after driving the car, that's why you're only supposed to fill it halfway. As long as it's not overflowing I'd say you're fine, you can replace the radiator cap if you're really worried.

Thanks for the response! Right now the coolant is right below the full mark. I know that sometimes the coolant in the overflow tank will fill up, but to be honest I never knew how much it would fill up. The reason I was concerned is because on Monday when I came home from school, the overflow tank was about 75-80% full and I heard a gurgling noise comming from the radiator. On Tuesday, I came home from school and the coolant level never changed. You also make a good point, it was not overflowing and it was not boiling so I let it go. As your suggestion, I will switch out that radiator cap soon.

 

[Hundred]

Symptoms sound like a sticky thermostat, but I see you have already replaced the thermostat. There could be some other blockage. Have you flushed the cooling system? I like to use distilled white vinegar. Then refill the system 25/75 antifreeze to distilled or deionized water and add a bottle of Water Wetter (or a similar product). You may want a different coolant ratio depending on the weather where you live, but generally less antifreeze cools better.

This weekend I may flush the system and thank you for the directions on how to properly do it. I think last time I did it, I did it wrong...I think I added more coolant than water.

 

[CheeseHelmet]

Thanks for the response! Right now the coolant is right below the full mark. I know that sometimes the coolant in the overflow tank will fill up, but to be honest I never knew how much it would fill up. The reason I was concerned is because on Monday when I came home from school, the overflow tank was about 75-80% full and I heard a gurgling noise comming from the radiator. On Tuesday, I came home from school and the coolant level never changed. You also make a good point, it was not overflowing and it was not boiling so I let it go. As your suggestion, I will switch out that radiator cap soon.

It should go back down, that's not normal. I suspect a new cap will fix the problem, if not you may have a leak somewhere in the cooling system.

 

[Hundred]

Took the car out for about an hour today. Got home and checked the tank, it was still at the full line!! One day the tank looks like it's going to overflow, the next it's normal......

 

[nyarsulik]

This is happening to my 2003 Protege 5 as well... The overflow fills with boiling coolant and actually almost explodes. The pressure makes the plastic overflow tank bend out of shape... The car runs fine on short trips, but if I get on the highway for any extended period of time it starts to overheat like this.

The coolant in the radiator is full, and the overflow is at its appropriate level before we go anywhere, so I don't think there is a leak in the system...

Do your radiator fans turn on?

 

[CheeseHelmet]

This is happening to my 2003 Protege 5 as well... The overflow fills with boiling coolant and actually almost explodes. The pressure makes the plastic overflow tank bend out of shape... The car runs fine on short trips, but if I get on the highway for any extended period of time it starts to overheat like this.

The coolant in the radiator is full, and the overflow is at its appropriate level before we go anywhere, so I don't think there is a leak in the system...

Do your radiator fans turn on?

I'd check your thermostat, it sounds like it's stuck closed.

 

[pw~mp5]

^ +1

 

[nyarsulik]

Thanks! After reading a little more I found a few more posts with similar issues. I just recently completely filled the radiator and overflow with new coolant, would it be OK if after I drain it I pour it right back in? I would hate to spend $100 for a flush if I don't have to, and I am having trouble finding a place that will take the used coolant to recycle it...

Other than that, is it difficult to replace the thermostat?

Also, how big of a bucket do I need to have ready when I drain it?

 

[CheeseHelmet]

Thanks! After reading a little more I found a few more posts with similar issues. I just recently completely filled the radiator and overflow with new coolant, would it be OK if after I drain it I pour it right back in? I would hate to spend $100 for a flush if I don't have to, and I am having trouble finding a place that will take the used coolant to recycle it...

Other than that, is it difficult to replace the thermostat?

Also, how big of a bucket do I need to have ready when I drain it?

I wouldn't re-use it, coolant is so cheap. I don't know about where you live but in Quebec garages are required by law to accept fluids for recycling at no charge. If not, just leave it by the door of a walmart garage late at night

The thermostat is very easy to replace, it's located on the left side of the engine (if you're looking straight at it) under the cap where the rad hose is connected. There's one or two bolts to remove and you'll have access. Check the service manual for all the details.

The part is about $25 from Mazda, you don't need a gasket or any RTV; the thermostat comes with a seal already on it. As for bucket sizes, I don't know. Check the "capacities" section of your owner's manual.

 

[P-Funk!]

I fear it is a cracked head or bad head gasket.

Have a shop 'sniff test' for exhaust gas at the radiator cap.