My 94Z28 is overheating when idle (after driving) but returns to a reasonable temp when driving. My question is... could an improperly bled system have anything to do with the problem OR would it overheat during driving also if the system was not bled.

 

Sounds like your fans are not working properly. Air flows through the radiator while driving which keeps it cool, but the fans move air while idle. If they aren't coming on that could be the problem. That is what I'd check first.

 

What temperature are you seeing that you consider to be "overheating"? What do you consider "reasonable" - in numbers?

 

The "overheating" is based on the guage being a hair away from the red. "Reasonable" for me would be back near where it has been operating which is a little more than midway between 160 and the halfway mark.

Forgot to mention that in the past the guage would get up to near the midpoint when idling but usually not past it like it's doing now.

 

i have been having the same problem to.. anyone know? whts going on

 

I am having the same exact problem. I just had my water pump and thermostat replaced and it is still doing it.

 

It's normal for a stock LT1 to heat up while stopped, or in slow moving traffic. By stock I mean no low temp t-stat or reprogrammed fans. The temp gauge might even get to the third hash mark before the fans come on. Once moving, such as on an interstate, the temp will stay much cooler. Bleeding the system could be done again just to make sure no air pockets exist. Look at the radiator from underneath the car to be sure no obstructions are there, such as a plastic grocery bag that may have been picked up.

 

I can understand that but what I don't understand is why it would just start doing that. I can't ever remember it going much past the midline (maybe halfway between the second and third mark) at idle even in the hottest Florida weather. However, my AC is out. The clutch is still engaging but it's got a leak from the low pressure valve and is not fully charged. Just blows hot air. Should turning on the AC still operate the auxillary fans even though it's not blowing cold air, and if not, is that part of the cause of the higher temps. This thread was originally meant just to know whether I can rule out air pockets as a cause of the problem...but since people have offered other advice I'm happy to take it.

 

If the a/c compressor does not engage (or is locked out by the PCM because of low pressure), the fans will not engage when the a/c is turned on. Only temperature will control the fan ON times. The low fan setting is 226 degrees.

 

Sounds like when my water pump was dying.There is a sensor I think on the radiator that goes south as well.Hope this helps.What codes are you getting?

 

The only sensor on the radiator is the coolant level sensor. Those die a natural death on a routine basis, but have no affect on the cooling system (unless of course the coolant level is coincidentally actually low).

 

Don't have a scanner for codes.

 

Don't you have an electric fan on the car? I had the exact problem on an IROC and it turned out to be a cut wire to the fan motor.

 

The sensor on the radiator does not set a code, it lights up it's own light on the dash.