Still Overheating, Please help

1995 Pontiac Grand Am Quad 4 approx 160K Car is overheating and I have tried everything to fix it, but it still overheats and I need some advice.
Here is a list of what has been done and in the order that it was done.
1. Fan blower motor was replaced, and the fan works fine, comes on when it is supposed to. 2. Thermostat replaced. 3. Complete coolant system flushed out. 4. Head gasket replaced (apparently there was a small leak), and head was sent for pressure test by GM, and it came back fine. 5. Radiator replaced. New cap on the coolant reservoir.
Also the water pump was checked and it is working fine.
None of these has fixed the overheating problem, and I don't know what else it can be. The temp is fine at highway speeds (about 1/4), but as soon as I get off the highway the temp goes above 1/2 and it is evident that it will go into the red if I don't cool it off right away. So I stop and open the radiator and let the steam out and also coolant comes out as well, but I do it very carefully using a towel. The fan stays on, and after about 5-10 minutes the fan turns off, and the temp is back down to 1/4. I am so frustrated because it is costing alot of money for the garage to do all this, and it's still no better than when I first took it in over a week ago. If anyone has any suggestions at all, or has experienced similar problems, I would really appreciate any advice or comments. To those in the pontiac group that have allready offered advice previously, I thank you, and I have tried everything that has been suggested thus far.
Regards, KDawg
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Sounds like the cooling system is still clogged.
My suggestion is to take the thermostat out and see how the car does. That will simplify the trouble shooting.
Also, take off the radiator cap and let the car warm up, and watch the coolant flow through the radiator. You should see coolant flowing while the engine is running. If you don't see a good flow, then the cooling system is still clogged.

else
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I haven't checked it since they put the new radiator in, but the tech called me and said their was little circulation before. Now with the new radiator he said the circulation is much better. The last thing that was done was the new radiator. They suspect that it might have some air pockets in the radiator. Is this common since it is a brand new radiator ? I will have to wait and see what they say tomorrow. I went over this evening after they closed and I took it out for about 20-30 minutes, and it was still overheating. What all should I have them check ?
Regards, KDawg

it
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KDawg wrote:

Have someone use a real temperature gauge on the system: either the type that screws in or an external infrared type. Have someone use a combustion gas sniffer on the open coolant reservoir.
BTW: One of the worst things you can do is to open the cooling system cap when the engine is hot. You're going to get a warped or cracked head doing that. A 15 lb. pressure cap raises the boiling point of water to 250F.
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Could this be a faulty intake manifold ? Just a thought.
Regards, KDawg

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This is just a thought...... a few years ago I had a Ford LTD....which continuously overheated. Tried a bunch of things to no avail. Finally replaced the FAN, fan was a variable flex type, which, (sheesh, it was so long ago, I forget exactly how it worked,) but I remember the fan using a fluid coupling instead of a mechanical coupling,
Fan was turning but the fan blades were slipping and not giving enough cooling power. Car ran fine at high speeds, with airflow providing the cooling power, but when brought down to side street speed, the car would overheat.
Just a thought.

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I got the car used about 4 months ago, and the thing ran great. The temp rarely ever went above 1/4 on the gauge. Evn on hot days it was fine, and the odd time it would go up to 1/2 if I was idling for a bit. Then all of a sudden the temp went up into the red. I took it in, and they said the fan motor was gone, which made perfect sense to me since it was fine on the highway but overheated while going slow. It has been quite cool where i am for the past 2 weeks, and I have taken the car out late at night when it has been very cool and it has still overheated. I have also verified with another user on Newsgroups who has the exact same car and he said that his never goes above 1/2. Thanks for the response. I am seriously starting to lean towards a thermostat problem. Even though they replaced it about a week ago, I think it is getting stuck, or the sensor is not working. When I checked the air between the fan and the engine it felt cool, so I am guessing that there is no circulation. It's a new rad so I know that rad is probably fine. The fan comes on about 1/2 way up the gauge. I have verified this by idling the car in my driveway and noting when the fan comes on.
Regards, KDawg

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"KDawg" wrote

idling
Ok....does the temperature continue to just climb right into the red zone if you let it idle long enough? That seems to be what you are saying, but I'm not sure. If the temp continues to climb even with the fan on...then yes, you do have some sort of problem. And if, as you say, the air that the fan is pushing feels cool, then I would agree with your assessment that there is a circulation problem.
Just want to be sure you aren't chasing your tail for nothing.
Ian
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I'm gonna have to go with Shi on this one but with a small twist Have you checked to see if the coolant temp sender was damaged during one of your earlier overheats May be as simple as comparing the ECM input of Coolant temp to the guage on the dash I have seen a number of these senders read way off after they have been overheated
Just my 2 cents worth............................. Good Luck
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My dad had an 84 z28 that was like that. I think it might of had something to do with rust building up in the cooling system because the coolent was never kept up. Have you tryed a very thorough flush of your cooling system and replacing the sending unit? Pull the drain plugs at the bottom of your block as well when you do a flush.
@verizon.net says...

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I know this sounds like a bad advertising pitch but this shiz works, points of example being my Fiero's cooling system, and all the Holden Commodores that have been in my family...
RMI-25 is by far the most ninja cooling system additive you can use, it cleans up the crap and keeps the coolant clean - the Fiero's 3800 is beautiful clean inside thanks to this stuff, far cleaner than most other 160,000km 3800s I've seen inside.
Nick.

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Have the rad hoses been checked? Years ago they had an inner liner that would peel off and block the flow. A mechanic could give the hose a squeeze to tell if it was bad. Not sure about today's hoses.
Bob

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Yup its an electric fan, and it comes on when it is supposed to. Somewhere around 1/2 way on the temp gauge it turns on, and it stays on after the car is turned off if it needs to cool down further.
Regards, KDawg

done.
when
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right
using
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Yup its an electric fan, and it comes on when it is supposed to. Somewhere around 1/2 way on the temp gauge it turns on, and it stays on after the car is turned off if it needs to cool down further.
Regards, KDawg

done.
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using
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check your engine timing

still
head
what
took
tried
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Seems to me...
1. You didn't have a problem until the radiator fan motor quit 2. You still only have a problem at speeds at which your cooling system depends on the radiator fan for airflow.
My guess is you still have problems with air flow from the fan.
I can't find where you said whether you have the AC on when the problem happens. I believe your car probably has a second radiator fan that operates whenever (and only when) the AC is on. Have you tried turning the AC on when it starts to overheat to employ the additional fan? Does the AC radiator fan work?
KDawg wrote:

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i have two suggestions. 1.please check if your sensors work fine 2. Try to check evaporator/condensor of AC system. I'm talking about the one which sits right infront of the radiator. It might be dirty, and does not let the air pass through it to cool the radiator.
checking upper radiator hose will tell you if the thermostat works fine. you can consider buying lover Temp thermostats.
good luck
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