I want to drop my engine temp about 20 degrees. Everything is working the way it should, but when I'm driving for 45 minutes+ on the freeway, my temp is around 240. 220 is normal for my car. I have flushed and cleaned the radiator inside and out. Tested the Themostat and it works. The stock water pump is moving water. My Air dam is intact. So I'm wondering if a performace water pump would help enough to drop the temp?

 

my 89 had cooling problems as well...as you said driving down the highway for awhile it gets hot. i installed a manual fan switch thats on all the time as well as a 160 thermostat. i also removed the ac condensor seeing as how my ac doesn't work anyways. now it runs at a steady 160 and performs like a dream

 

My AC works so I don't want to remove my condensor and the fan is belt drivin' so it alway runs as the engine turns.

 

You could try taking the rubber weather strip off at the back of the hood near the winshield. That will let more air out from under the hood..

 

The space between the A/C condensor and the radiator could be clogged.Take the top section of the fan shroud off to check this.S
Since your fan is belt driven you could have a bad fan clutch.Although this would cause a problem that would be more prevalent below 45mph.
If the cooling system has been opened you may have an air pocket in the cooling system that would need to be purged.
Try this article in the Tech section: https://www.thirdgen.org/overheating

 

One other thing to check is that the air dam under the car is in decent shape. This is vital on our cars.

 

What would a Performance water pump do compaired to a standard pump?

 

It MAY flow too much ? Meaning too quick, not enough time for the water to cool off in the radiator before it heads back into the engine ?

I've actually been wondering about this myself, stock replacement or one that flows a supposed 30 percent or so more ?

 

It's the thermostats job to keep the coolant in the radiator long enough to cool down. Likewise, long enough in the block to absorb heat. All a higher flow rate does is move water around faster.

 

I would try one of those Jet Fan switches that turns your fan on earlier firs ir your Air Dam is in good shape. I ended up putting a new radiator in myself and that took care of all my cooling issues.

 

The OEM pump is more than enough for these cars. Flows well, reliable, replace 'em about every 75k and you'll never have a problem there. Unless you are running a HIGHLY modified performance engine, which you arent. I'd look elsewhere for the problem. Like 90tararebird said, a good airdam if vital for our cars. 220-240 is WAY too high for highway speeds, that's almost a sure sign you have an airflow problem. Should be right at where your thermostat opens, or less. So, verify that your guage is right (GM guages are NOTORIOUSLY innaccurate as they get old) verify that you have plenty of coolant, AND the right balance, i've seen cars that someone dumped PURE antifreeze into do what you are describing. Water is the BEST coolant, pure antifreeze can gradually heat-sink your car. Check that you have an intact airdam, (make sure it's not so weak that it's actually FLAPPING at speed and therefore disrupting the airflow) and no blockages in front of your radiator. Now, you could ALSO have a weak water pump (though that's rare) or the system could be partially sucking shut one of your hoses. Does it have a problem around town? Or just on the highway?

 

radiator is plugged up, coolant flow is minimized while engine rpm is higher.