2005 impala overheats when its driven, normal temp when idling

[jollyGIANT6'7"]

Ive replaced the radiator, water pump, and thermostat on a 2005 impala 3.4L. Drove it yeaterday, and it started overheating. Thinking i may have to flush the whole system.....Any ideas?

 

[HarryLui]

If your radiator fan coming on?

 

[KIAman]

Probably not the fan if driving causes overheating. Can you do a pressure check on your coolant loop? Try to ensure there is no air or clogs.

 

[dave_the_nerd]

If you replaced the thermostat, radiator, and water pump, then you got a flush - all the coolant falls out when those parts come off.

First things first, yes, check to make sure the radiator fan is coming on at idle. Make sure all the cords are plugged in, etc., make sure there's no air in the coolant.

It's possible the thermostat is defective. (New parts, yeah, but it happens.)

It's also possible you're getting insufficient airflow around the radiator at speed - you generally shouldn't need the radiator fan on when moving at >20mph, especially in the winter - there might be something blocking it, though. Are you one of those cardboard-on-the-grill people?

 

[jollyGIANT6'7"]

If you replaced the thermostat, radiator, and water pump, then you got a flush - all the coolant falls out when those parts come off.

First things first, yes, check to make sure the radiator fan is coming on at idle. Make sure all the cords are plugged in, etc., make sure there's no air in the coolant.

It's possible the thermostat is defective. (New parts, yeah, but it happens.)

It's also possible you're getting insufficient airflow around the radiator at speed - you generally shouldn't need the radiator fan on when moving at >20mph, especially in the winter - there might be something blocking it, though. Are you one of those cardboard-on-the-grill people?

Nope. Not a cardboard person. I was thinking that the thermostat may be junked up. If its not, how would i flush the whole cooling system? Never done it before.

 

[jollyGIANT6'7"]

Probably not the fan if driving causes overheating. Can you do a pressure check on your coolant loop? Try to ensure there is no air or clogs.

Do i need a pressure gauge to check it?

 

[dave_the_nerd]

Nope. Not a cardboard person. I was thinking that the thermostat may be junked up. If its not, how would i flush the whole cooling system? Never done it before.

It's not difficult - no wrenching required. Basic directions are here:

http://www.dummies.com/home-garden/...em/how-to-flush-your-vehicles-cooling-system/

But every car is a little different - some you have to jack one end up higher than the other to ensure that everything drains out right. That's where you want to check for directions in the manual, or buy/borrow a Chilton's manual or something. Youtube is also useful.

If the shop that did the work left air gaps in your coolant, it would cause this.

 

[hdfxst]

is the plastic bib under the bumper there?Sometimes they get torn off and You need that to deflect the air through the radiator when your moving.

 

[BStorm]

A flush isn't really necessary, given that most of the cooling system was already emptied (save for some in the block and heater core).

Dave is on the right track with air trapped in the system. The coolant can't circulate properly, causing overheating.

The 3.4s are tricky in that aspect. There are two bleeders in the cooling system that have to be cracked or it won't properly bleed. One is located on the water pump bypass hose, and one on the thermostat housing.

This video gives a good walk through on what to do:

https://www.youtube.com/watch?v=ad9u8jADrvU

Good luck.

 

[dave_the_nerd]

Dave is on the right track with air trapped in the system. The coolant can't circulate properly, causing overheating.

KIAman mentioned that possibility first.

 

[boomerang]

Is the air dam below the front fascia still in place? A lot of cars and especially one's of that era required that air dam to funnel air through the radiator. With it missing or severely damaged, that does not occur.

Oops, just read Post #8. It's already been covered.