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heaters blowing nothing but cold air and motor overheating

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New User

Feb 28, 2010, 2:24 PM

Post #1 of 6 (22701 views)
heaters blowing nothing but cold air and motor overheating Sign In

I have a 2004 Chevy Impala 3400 V6 it has 122985 KM on it. Here is our situation we had driven in to Vancouver from Abbotsford to check out some Olympic festivities we parked in a suburb close to Vancouver so we could take the skytrain in when we came back we started the car with no problems yet we did not drive 15 km before there was a signal telling us that it was overheating. We managed to cool it down we checked the coolant level but we had no light and no way of telling us if it was full or not there was no Low Coolant Symbol on our dash indicating a problem, not having coolant on us we put some water into the overflow container just in case it was low, once the gauge said the motor had cooled down we were able to drive 30-35 km before it gave another overheating symbol. At that time we pulled the car over and called a tow truck and got a lift to the nearest gas station we let the car cool down as well. During this time of overheating the car was continuously blowing cold air through the heating vents. When we left the gas station the car temp was 80 deg. and the heaters were working this was Saturday night. On the following Monday I changed the Thermostat gave the car an Oil Change and yet the heater is still not working and the temp say's that it is still overheating. What should I attempt next. I have never noticed anti-freeze on the drive way nor a major loss of anti-freeze I am at a loss should I change the coolant sensor next? the actuator? could it be the heater core if it is does it need to be replaced?
There has been no large amounts of steam any of the time the gauge said the temp was to high. I hope this is enough information.Mad

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 28, 2010, 4:47 PM

Post #2 of 6 (22689 views)
Re: heaters blowing nothing but cold air and motor overheating [In reply to] Sign In

What was it the shop did that put it back in order?

It does seem to be overheating as when so and boiling or low coolant unseen perhaps in the engine itself and in either case will blow cold. Boiling (even though hot) is vapor and doesn't transfer heat for diddle.

Reasons include: Low coolant for any reason would make heater quit and the overheat. Overheat alone can cause loss of heat.

Why? It's losing coolant no doubt somewhere. It could be only while underway and might not leave obvious evidence.

Sneaky losses can be anywhere but could include the water pump, hose or anything sealing system, or a head gasket adding vapors into cooling system which will behave like air if so.

I don't think you have a cap to fill radiator and know the engine side is in fact full and it could work for a while. The recovery tank if with pressure cap on it (I think this is that style) doesn't give accurate info of how full the system as a whole really is if there's a problem which there is.

I would pressure test the system looking for forced leaks to show themselves and check for exhaust gasses in cooling system. When you changed the thermostat it can be a job to really fill the system via an air bleed or some may want a high hose removed to fill properly. There is a fancy vacuum device that will suck coolant in that DIYer wouldn't likely have to speed up true filling of system or you painstakingly go thru hoops to get it full or back to no heat and overheating.

If no evidence is found I would test out head gasket issues with the sound of this so far,

Long retired now

New User

Feb 28, 2010, 6:09 PM

Post #3 of 6 (22684 views)
Re: heaters blowing nothing but cold air and motor overheating [In reply to] Sign In

There was no shop it was a gas station in the middle of the night and all we did was put some more coolant in the reservoir. We waited 20 min's turned the car on the temperature was fine to drive there was heat coming out of the vents and it appeared to be a one shot deal. As our trip was about 39 km long. Another thing that may be of interest is that the temp. gauge takes along time to start moving and when it does it slowly goes to 80 degrees than climbs steadily to the overheat stage.

Veteran / Moderator
nickwarner profile image

Feb 28, 2010, 9:23 PM

Post #4 of 6 (22678 views)
Re: heaters blowing nothing but cold air and motor overheating [In reply to] Sign In

Your engine is notorious for both intake gaskets failing and head gaskets. Look at each end of the motor for leaks. If you can, pressure test the coolant system while warm. Like tom said, you lose heat when coolant level drops. The coolant is obviously going somewhere. That needs to be fixed. Don't put any more water in the motor. Thats asking for trouble. When you changed the thermostat, how did you bleed the cooling system of air?

New User

Apr 7, 2010, 11:56 AM

Post #5 of 6 (22625 views)
Re: heaters blowing nothing but cold air and motor overheating [In reply to] Sign In

hey Tom what would be the side effects of just taking the thermostat out of a 99 chevy malibu.. cause mine is over heating. i know you can turn the heater on and it keeps the car cooled down but sometimes the heat doesnt even work. one minute its blowing hot air the next cold. like it has a mind of its own. well im just really short on cash so i just do like ive always done. removed the thermostat. and just make sure i got a new one by winter or fix the main problem. but this year ,and make its like every thing i thought i new about cars dont apply the 99 chevy malibu. oh yeah i already removed the thermostat and it did help its not over heating im just scared to turn the heat off . my main concern is if im doing more damage than good by removing the thermostat.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Apr 7, 2010, 1:58 PM

Post #6 of 6 (22621 views)
Re: heaters blowing nothing but cold air and motor overheating [In reply to] Sign In

Just said this elsewhere about taking thermostats out. Not an option or a cure and can cause incredible damage! The hole it goes in would be many times what the water pump could overcome to mix coolant within the engine so it just plows one end, satisfies the sender so you think it's running cold (maybe) and fools computer too adding more fuel than needed so you can now put a new pipe and converters, o2 sensors on the list as they won't last long with the extra fuel and still need to fix the cooling problem - yikes!

Nick mentioned this engine is known for gasket problems and it probably does add air into the cooling system which would purge out faster without a thermostat which would lock air in till hot enough or if already too hot would boil so you are stuck with the air again.

Seems silly but so important but just filling cooling systems can be a real hassle especially ones that don't use a pressure cap on the radiator. Some will have bleeder ports just before the thermostat or you might need to remove a hose to fill engine side enough or you get an instant overheat and risk head/intake gaskets right away anytime you overheat. This engine like most now is made of dissimilar metals which expand and contract at different rates than the old days when the whole engine was cast iron and tolerated much more abuse. The gasketing can only make up for so much and then it's game over for the gasket or worse warp or crack heads,

Long retired now

heaters blowing nothing but cold air and motor overheating

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