kellefitz

Hello all. I will try not to go on and on...

6 months ago I was driving across the state and the car was running fine but when I stopped for an accident, the temperature began rising and I could hear the overflow tank gurgling, the add water light turned on and the overflow began running over. I pulled over, let the car cool down and added water. This ran just fine until I was slowed down again, then the same thing happened. I was able to repeat the procedure until I was able to arrive home.

After some research we began replacing things; water pump, thermostat, holding tank cap, fan relays and sensors. These things did nothing to fix the problem. Many people ask about the head gasket; there is no water in the oil and no white exhaust from the car. At this time we have not replaced that.

I have a friend that is a mechanic and asked if they had any ideas. She came over today and worked on it a little bit. We did some research to find that when we replaced the water pump we were supposed to bleed the tank. We followed two different posts on how to do this and did it.

The add water light did not turn off. We bled the system as instructed and the temperature gauge now stays right at the half way mark as it used to, it does not indicate that it is overheating. We went for a few short drives and were getting pretty excited. Water was staying in the car and it was staying below over heating on the gauge. We hopped on a short stretch of freeway, did just fine, headed to the grocery store and as soon as I stopped moving the same gurgling and overflow. I turned the car off and the overflow was boiling over...

Details... my engine is the V6... the boiling over happens at an idle... I can run the heater and the a/c while driving and there is no fluctuation in the temperature and it does blow heat or a/c.

I love my Malibu, but I'm beginning to think it doesn't love me. Does anybody have any ideas? Thanks so much.

EinST

Welcome to the forum. Is it dependent on the engine RPM (coolant flow rate) or vehicle speed (air flow through the radiator)? What happens if you rev the engine when stopped? Do the cooling fans run, both of them? They run at two different speeds depending on the engine coolant temperature. They'll start running at the low speed at a set temperature and then scream at certain higher temperature.

kellefitz

The fans do not kick on when idling... even when I rev the engine. We did replace the fan relays because of this. The fans will kick on if you turn on the a/c, so the fans do work... just not when we need them to I guess.

EinST

So, the PCM won't turn on the fans when it's supposed to. Get both the PCM and BCM scanned for trouble codes and go from there. That would require a professional level scan tool.

Inicio

Any updates?

My 02 Malibu has similar symptoms..A month ago it would start overheating because the fans would not start and as I drove above 45 mph it would cool down. after a check of the pcm I changed the thermostat and everything went back to normal although I noticed some red/brownish gunk in the old unit so I flushed the system as well. After that, everything has been fine until a couple of days ago it started to overheat a little. Apparently the fans start running at the low speed by ~200-210 so I can hear the overflow tank burbling and spilling coolant. The coolant doesn't seem to have but a little bit of gunk (probably stuck leftovers).

EinST

Welcome to the forum. A couple of things come to mind. Are you going by the temperature gauge in the I/P cluster? Ever hung an OBD scanner and read out the ECT as determined by the PCM? Also, the coolant recovery tank shouldn't be boiling over that soon. Check the concentration of the coolant and try a new cap?

Inicio

Yes, I am going by the gauge in the I/P (when I got it checked for the first time with the professional scanner it showed to be reading correctly). The concentration was somewhat more diluted than 50/50 since I live in the tropics, although ever since this started I'm only pouring water until I get the problem resolved. Is the overflow drain valve blocked by the cap (to pressurize the system)? If so then I am going to give it a try.

EinST

Yes, try a new cap. Also, as you move away from the 50-50 concentration in either direction (too much or too little water), the boiling point of the coolant mixture goes lower, i.e., it tends to boil over at a lower temperature. It doesn't sound like there's anything wrong with the ECT sensor nor the PCM. The fans engage in the low speed operation at 106°C (223°F) and then the high speed operation at 110°C (230°F).

Inicio

Ok, putting a new cap didn't work. As soon as i parked the car for work the reservoir was gurgling and spilling water/antifreeze on the floor. The temp was at about 200*F. I had put in about 1/2 gallon of water and lost about half of it. What I don't understand is that if even water alone should start boiling at 212F at atmospheric press., at 15 psi above atmospheric it should boil at a higher temp. So why on earth is this happening? My last resort will be to hardware the fans to turn them on always but I want to exhaust all my options before that.

BTW. Does anyone know if there is a way to either reprogram the PCM or to build a temperature-based circuit in order to make the fans automatically turn on at 190F? Thanks

EinST

You did bleed the air out when you did the drain-and-fill, didn't you? The air bleed valve is located on top of the thermostat bypass pipe near the thermostat housing. Consider getting it diagnosed properly since you might be looking at a head job. The "gurgling" might be the exhaust gases escaping rather than the coolant boiling over.