New to the forum, my buddy has a 2001 monte Carlo SS with the NA 3.8L. (I joined this forum because he's not very mechanically inclined:p) I drive a GTP.

1. First issue, "over heating"...Sitting at a red light, coolant temp. climbs just over the half way mark on the guage...start cruising around 35-45, and the needle returns to normal operating temp.
The Low Coolant light comes and goes, so I added some coolant. Not noticing any leaks anywhere. I'm guessing there some air in the system?? or could there be a small leak and the coolant burns up before touching the ground?? Are there any common gasket issues (i.e. throttle body, LIM) Any suggestions on what to check? I haven't had much time to look at the car myself yet, just thought I'd get a head start on some suggestions.


2. Second issue, "noise"... Car is at operating temperature, driving the car to about 35-45, and as I let off the gas and start to slow down, I noticed a slight humming noise (sounds like when an electric motor is winding down) I thought at first it was just an abnormal idle down, but the RPM gauge seems to be showing normal RPM's. You cannot hear the noise while idling, only audible really during the deceleration, i'm assuming it makes the noise while accelerating but you can't hear it over the exhaust during acceleration.

The car has a 103K... Sorry for the long post!! Thanks

 

for thehigh temp, these cars a prone for LIM and head gasket failures. i'd check the simple things first. make sure coolant it full, make sure air is out of system, then i would so a pressure check on the system. the majority of time i've seen these cars leak internally so you may have a blown gasket but won't see any external leaks. also check the oil. if it's going to fail internally you will see it there. if you see a tan milky substance, you have oil and water mixture, of if the oil level is high, you are getting the coolant dumping in the oil pan. but depending on how long he;s been having an issue or how bad it is, you may not notice it.

 

I thought it was the 3400 that had major intake gasket leaks.. but you said head gasket... so I take it you're still talking about the 3800?

Is the radiator fan working properly?

 

The 3800 is not really prone to headgasket issues, but is notorious for LIM gasket issues. Its basically one of those "its not a matter of IF the LIM gasket will start leaking, its a matter of WHEN the LIM gasket will start leaking" situations.

The humming noise you are describing sounds very similar to the noise we were hearing come from my mom's Bonneville when the front wheel bearings went out. Based on what you are describing, and the mileage on his car, I would check into bad wheel bearing hubs.

 

If you have a GTP use that knowledge to help :P

I would have him do a full flush of his coolant system (good chance there hasn't been one) and it should really be done every year. Every OTHER year as a MINIMUM. Could also have a thermostat starting to stick? Replace that, do a coolant flush and see if there are any more problems. If there are, then a great little pressure test will be required to find a leak.

The noise, it could most likely be a bearing... these wheel hubs like to play games a lot. I would drive on it longer, until it's a problem if no lights are popping on yet.

 

Overheating plus a humming noise? Sure sounds like a failing water pump to me. Inspect the water pump pulley while the car is running- is it "wobbly" appearing? When the bearing fails inside the water pump pulley, it will begin to make strange noises at certain RPMs. It also won't cool as well, especially at lower RPMs.

 

My car started this same overheating issue 2 days ago. I have never had any problems with it before and now it's starting to overheat. My fiance and I were in the drive thru at chik-fil-a 2 nights ago and my temp gauge started to climb and its been doin it ever since. He checked my coolant level and it was a lil low so he added some, but it is still overheating. We checked my oil this mornin and it looked fine as of right now, he said we are goin to keep an eye on it to see if it continues.

 

The overheating could be a couple things. Head gasket (not very likely, but still a possibility), LIM gaskets gone bad, UIM gasket/UIM warpage, or the water pump.

The humming on deceleration could be a number of things. Maybe the alternator going out?

 

i would say if you have a hum doing speeds between 30-40mph the engine is under load. i would say the water pump bering is getting ready to go when the engine is off check behind the pully of the water pump if there is signs of dampness. if you feel a little of it it is the pump. also i would change the thermostat as well to advoid it breaking when you replace the water pump. my water pump on my truck made the same noise that your talking about as well also the temp was going up then drasticully droped when i started to move. also check if there is a yellow or greenish collor on the casing of the altinator. the reson why i say that some water pumps when failing will burp out and sling coolent to the nerest thing

 

Try replacing the thermostat, and flushing to coolant.