'99 Malibu Cooling System

[adrenalin2k4]

Here is the situation. My '99 Malibu 3.1L (W) Automatic Transmission is overheating.

When i first bought the car i noticed that i wasn't getting any kind of heat in the car at all from the heater. I looked under the hood and the hoses that went to the heater core was cut and re-routed back into the engine. I know it is a standard practice when a heater core goes bad. So i had it replaced and installed 2 new hoses. I also noticed that the car was running a little hot. I would get heat in the car, but, it was intermittant. It would be hot air and then for some odd reason it would get cold for a while then hot again. So i replaced the Thermostat. Then i noticed that the water flow was almost null at an idle. So i replaced the water pump and then decided that ever since i had the money i went ahead and replaced the radiator as well.. The car still overheats badly and now quicker than what it did before. At an idle in the driveway it doesn't over heat at all. But, when i get out on the road and go about 5-7 miles the temp will shoot up and the temp light comes on and the needle is pegged in the red. So... i pullover and let the car cool off and add some more water and it does well enough to get me home. By that time it is hot again. It will also do this with the Thermostat out of it, but, not quite as fast.

When i had the radiator out of it, i decided to check out the cooling lines to the transmission. I blew some air into on of the lines and it would do nothing. Possibly could be stopped up???? But, is very cool to the touch. But, i do not think it would let the car get hot enough to overheat.

I know to turn the heater on full when the car gets hot. But, that doesn't work at all. There is no hot air coming from it and at a stop light and then will get hot again when i take off. Then when i go down the road it will get cool again then hot again.

What is wild about it is that the air plenum will be rather cool to the touch amongst other things. The valve covers will be hot but you can touch them briefly for a few seconds.

I have looked then engine over and haven't seen a leak anywhere at all. The is no oil is the coolant or coolant in the oil.

I have noticed that someone before me had to replace the intake gasket or just patched it up with that orange RTV sealant. The compression is perfect and there seems to be no leak anywhere around the intake gasket. The car runs to darn good with no sputter or erractic behavior except for the overheating. I wonder if the temperature sensor is bad? I think it may also be that a cooant port is blocked by a gasket between the intake and the heads.

It is beyond me what is going on with this car. I am a rather good shade tree mechanic. But, this has me baffled. I do not want to take it to a repair shop because of labor price involved. I did that with the heater core and the total bill was $722.14. The labor was $520.00. So would rathe do this one on my own.

Any thoughts, ideas or help is greatly appreciated.

adrenalin

[bcopeland]

Let me know when you find out because I have the same problems.

[RahX]

#1: the lower intake gaskets on those cars are notorious for leakage.
#2: even tho you bled the air teh best you could those things are a bear to get the air out of. the best way ive found to get the air out is to do this. fill the overflow to about 1/4in above the maximum mark. start and run the car till it gets warmed to normal temp. raise the rpms to about 1200 and hold them there until the gauge starts reading hotter than it should. when this happens rev the engine to about 2200-2300 and let off to about 1500 and repeat. so it should be like this 2200-1500-2200-1500-2200-1500. the temp should start dropping. if it doesnt stop and dont let it overheat. anyway after it drops repeat the process and keep an eye on the over flow. after you do this 3 or 4 times warm the car to normal temp and shut it down and DO NOT open the cooling system. let it cool off on its own, it will suck from the overflow but make sure the overflow is full. after its cooled down for about an hour or two start it back up and see if it overheats. usually you can tell how much air was in the system based on how much coolant it sucked down but ive found this method to be very effective.

[adrenalin2k4]

I am suspecting that it may be the intake gaskets. I just do not see any leaks at all.

I bled the engine until i couldn't bled no more. I even used the kit that i got from AutoZone. It came with a 5/16 plastic tube and it connects to the bleeder on top of the engine where the heater core returns dumps back into the engine. It is just too wierd for me. I had to keep on adding water/coolant and had no bubbles at all. What i did notice was the fact that the exhaust didn't have an exhaust smell at all. It actually smelled kind of humid or like boiling water. So that is telling me that i do in fact have a small misting leak, either with the intake gaskets or head gaskets.

So, what i am going to do is... go ahead and break the engine down to the block and inspect everything as i take it off. i have the time, money and patience to do all this and have done it before on a Grand Am that had a blown head gasket.

I seem to think that it may be in the Air Throttle. Yep, Air Throttle. There is a small cooling line that runs from the heater core return that goes through the carb and then back into the block. I seem to think that it may have a small crack that mists water into the air as the Air Throttle sends it into the Air Plenum. I think that it is sending just enough of a fine but steady mist into the Air Plenum that it mixes with the Air/Fuel and actually doesn't cause it to bogg or run rough and just turn into a non-visible steam caused by the Catyllitic Converter super heating it. I know it may seem far fetched? But, i have seen wierder.

I will be sure the post back and let y'all know the outcome.


adrenalin

[RahX]

those are to warm the throttle body, you can actually just block off the two nubbins there and youll be fine. ive seen models that didnt have them at all. but really, someone might have done the intake gaskets already. so i would try the method i explained earlier before you started digging into the engine unnecessarily.

[adrenalin2k4]

Well after trying that trick out for about 5 hours. I still wasn't able to remedy the problem with overheating.

However, it is still the problem of it Airlocking my cooling system. I found this out by going ahead and breaking down the top part of the engine. The Intake gasket was still good and posed no problem. But, i did notice coolant setting in a puddle on right side of the engine by where the old distributers would set. I went ahead and removed both of the heads and found my problem. If you are facing the front of the car it would be on the head closest to you. The gasket was crack in 2 places between the #2 and #4 and also between the # 4 and # 6 piston cylinders. The cracks was running from # 2 towards a coolant port and from #4 towards a coolant port there as well.

It only took me about 4 hours to break down the top of the engine. I have to wait until Monday to pick up the gaskets and get my heads checked out. But, to me the heads look just fine. I just wanna make sure that they are ok, so i won't run into any other problems in the future.

I will keep y'all informed on the outcome. But, i still am going to use that trick. So i can get the air out when i go to finish it up.

Happy New Years

addy

[adrenalin2k4]

Well, i got the heads back and there wasn't any cracks. But, there sure was some warpage. The right side was warped .008 and the left side was warped .012. The left side was the one that was pumping air into the cooling system and air locking it.

The car is in top notch condition now. It runs very well. i didn't have no troubles at all getting it back together. However, i do reccommend that if someone else has the same problem? That you buy new head bolts along with new exhaust manifold bolts. A few of the bolts that was on the .012 side was a bit out of round. So... be sure to change them there bolts as well.

I hope this information can be useful to someone else that has experienced the same troubles as me.

Oh... by the way. The car has 184792 miles on it and i do believe that i will wind up getting that much more out of it.

adrenalin