Thread: Airflow or radiator problem?

With summer heating up so is the engine. Temp stays normal at freeway speeds but as soon as I hit stop and go traffic it shoots up. Water pump is two years old. I flushed the radiator and didn't get much gunk out. Both fans are running when the AC is on. If I shut the car off but leave the key on the fans do not run when the car is not. I can't remember if they used to or not.

2001 Pontiac Grand Prix 3.1

I did that when I refilled after the flush. I was going to check it tonight to see if it needed a top off, I'll bleed it again to see if any more air has worked its way up.

Do you have a 180* thermostat?

Originally Posted by J57ltr

Do you have a 180* thermostat?

It's the stock thermostat.

Originally Posted by BillBoost37

Shoots up to what?

Fans are not programmed to come on (3.8L) until 212F/228F. Before I reprogrammed the fans on my various cars, I hated coming off the highway to wait at a light. Temps would go from 195 to 228 fast.

I can't remember the increments on the gauge at the moment but it gets up above the last mark. So far it hasn't hit the red yet but it did trigger the high temp warning the other day after a few short stops on my way home.

Checked last night and the coolant reservoir was empty. Topped that off and bled the system but didn't get any air. I think I'm loosing coolant somewhere though. From the battery down the passenger wheel well is covered in yellow. Can't find any leaks on the upper radiator hose or the overflow hose. May be a cheap replacement radiator cap from Autozone.

Fill the reservoir with water and watch it if you have air in the system it will need to purge out through the overflow, the 3.1 is notorious for bad lower intake manifold gaskets. Check the interface between the head and intake and you may see a leaker. you may also have a leak in the reservoir. this will cause the system to vent coolant and draw in air when the system cools down. This sounds like a more likely scenario as you mention seeing coolant in that area, the hose may also be leaking.

Jeff

Originally Posted by J57ltr

Fill the reservoir with water and watch it if you have air in the system it will need to purge out through the overflow, the 3.1 is notorious for bad lower intake manifold gaskets. Check the interface between the head and intake and you may see a leaker. you may also have a leak in the reservoir. this will cause the system to vent coolant and draw in air when the system cools down. This sounds like a more likely scenario as you mention seeing coolant in that area, the hose may also be leaking.

Jeff

I didn't notice any bubbles in the reservoir last night but I was going to check the level again tonight and see if I am still losing coolant.

Had the intake manifold gaskets done about 8 years ago, hope they are not a problem again.

Ok, just fill up the radiator and reservoir and take it for a spirited drive with the AC off let it get to temp. Come home and park it let it sit until it cools down (hours, and not the level in the overflow at this time). When you shut down the car the engine is still trying to give off heat to the coolant in the block and will do so until the pressure rises to the point where the rad cap vents into the overflow. After the car cools down it will suck the coolant from the overflow back into the radiator. After about an hour or so then check the level in the overflow again and see where it is at. also check the upper hose and see if it is tight or seems a little compressed this will indicate if there is pressure in the system or vacuum from the system cooling down. If the pressure is low leave it alone and allow the system to do it's job. Keep an eye out for leaks as well.


Jeff

I'll give that a try tonight. Would a sticking thermostat give similar symptoms?

A stuck closed thermostat would cause the upper radiator hose to collapse when you rev the engine. Usually they fail completely, most common failure I have seen is one side breaks loose and keeps it from opening. If you have a "failsafe" thermostat they typically have a hole in them that will allow a small amount of coolant flow, but hood open and rev the engine and it should still collapse the upper hose.

Jeff

The problem persists. Had a longer than usual stop and go commute in the evening on Friday. When I shut the car off it was almost at red line. Had coolant boiling into the overflow tank and some steam coming out of the cap. After it cooled down the level of coolant in the overflow looked pretty close to where it was at the night before. I swapped back to the stock radiator cap to see if the cheap one was part of the issue. On my way to work this morning it was already warm outside and by the end of my trip the engine was getting hot again. I had the AC running at the time.

Coolant doesn't boil out that sounds like it was purging the air from the system. It takes hours for the system to cool to the point where it will pull in air. Yes steam will come out at that point it was pretty hot after all but it's normal if you get air trapped under the thermostat. Put a box fan on high aimed up into the radiator to make it happen a little faster. The engine still ends up being hot and there is not a lot of heat transfer in fluid that is not moving. If you removed the radiator cap early then you end up back to square one. You have to let it do it on its own.

Jeff

Boiling was probably not the best word to describe it but it was flowing heavily into the overflow tank so that it gave the appearance of boiling water.

I tried to bleed the system again tonight. Car had been shut down for about 45 minutes. Turned it on and noticed the upper radiator hose was almost flat until I opened the bleeder screw.

YOU CAN'T do that! You just let all the air back in.

Jeff

Sounds like I don't understand the bleeding process. I have always opened up the bleeder screws a few times until no more bubbles and only coolant came out. What I am doing wrong?

If the hose is sucked in then it's under vacuum and about to start pulling through the overflow if the rad cap is working correctly. By opening the bleeder when you did you allowed air into the system then after the air comes in then coolant will come out a little bit.

open the bleeder either right after startup cold, or after the engine is warm. Then of no air comes out when it's warm leave it be.

Jeff

Originally Posted by J57ltr

Fill the reservoir with water and watch it if you have air in the system it will need to purge out through the overflow/ you may also have a leak in the reservoir. this will cause the system to vent coolant and draw in air when the system cools down. This sounds like a more likely scenario as you mention seeing coolant in that area, the hose may also be leaking.

Jeff

also re read this part.

and this:

Originally Posted by medicmandan

Checked last night and the coolant reservoir was empty. Topped that off and bled the system but didn't get any air. I think I'm loosing coolant somewhere though. From the battery down the passenger wheel well is covered in yellow. Can't find any leaks on the upper radiator hose or the overflow hose. May be a cheap replacement radiator cap from Autozone.