Couldn't agree less - there is nothing defective about the C4's cooling system as it left the Factory and works fine regardless of climate. Putting it back to that may entail new stuff - like replacing plugged up cores and heads and broken shrouds which have outlived their expected lifetime, but it works quite well when it's right. So much unsubstantiated folklore is posted around here you'd think that GM should have recalled the entire production. Modern (well it isn't that modern anymore since it's been this way for last 30 years) has normal, non a/c low speed operating temps in the 220's and you can check your Toyota with a Scanner if you think there is something different about your Vette. If these temps bug you, turn on the a/c (if that even works) and assuming it's right, coolant temps will be 8 to 10 degrees cooler.

 

Well I guess we can disagree!

My A/C works just fine (And even better since I dropped in a HD dual row DeWitts radiator) and why should I have to drive around without A/C when its 90* out? Because my engines cooling system can barely cool the engine in hot summer months without the added heat from the A/C condensor? Because the margin of error designed by GM into the C4's cooling system is razor thin, even when everything is working as designed.

Heats kills...... almost everything over time.

While your engines coolant sores to 240* What do you think the oil temp is? Is that temp. optimal for your engine? What about the tranny fluid temp? Do you think running w/ tranny fluid temps at 220* plus is good for the tranny? You do know that when your coolant is at 230* plus, the life expectancy of everything from your tranny, altenator, rubber hoses, vacume lines, anything in the engine bay made of plastic, internal bearings, and seals goes down exponentially!

Why run that hot if you don't have too? You plan on keeping your C4 around a long time, Right? Increasing the cooling capacity of the Poor GM design is an excellent idea. Turning on cooling fans at lower temps and dropping in a higher capacity dual row aluminum radiator makes for a better more reliable C4, especially when it's 90* in the summer with the A/C on full blast!

 

All I know is that I run 205 to 212 around town with the a/c on and yes that's even when we have a Santa Anas with 15% humidity and 112 degree temps. My vent temps are about 58 - 62 degrees on those days, but that's about what they should be. That's how it was when I bought it off the Dealer's Lot in Oct of '89, but keeping it that way - even with 60,000 miles - hasn't been without some pain. There are similar around here without any gizmos and I tried most of them when they were being crammed down your throat back in the heyday of the C4 (including the Throttle Body Airfoil though it has nothing to do with it). None of them are necessary. Our cars didn't leave the Factory with a Cooling defect though the quality of a lot of the OEM parts probably left something to be desired and I'm not so sure we're getting any better now.

 

Well your '89 must be very, very, special and quite the exception. Is your '89 bone stock? Do you have the factory HD cooling option w/ an auxillary fan? How can you possibly be running at 205*~212* around town w/ the A/C on at 112* ambient temperature??
Are you running an OEM 195* thermostat? GM designed the cooling system to run much, much, hotter than that! And therein lies most of our C4 cooling problems!!!

I also have an '89 L98 C4. How is that possible that your OEM '89 runs so cool?? The OEM ecm didn't kick on the engine cooling fan until 220*, and if equipped w/ an auxillary fan that didn't kick on until the coolant was a boiling 235*. My '89 would run well into 230*~240* under those same conditions. That was before I added an OEM auxillary cooling fan, ecm chip to turn on my engine fan at 175*, a GM 170* thermostat, and a DeWitts dual row aluminum radiator to lose all that excessive heat when running full A/C on 90* plus summer days! Now at 60 plus MPH on 90* plus hot summer days w/ the A/C blasting my coolant temps are under 200* and my C4 is much better for it!

 

Nothing special about it - it's all stock (except for 6 grand in paint). A/c has nothing, but then everything to do with Coolant Temp. What's rolling through the Condensor averages about 100 to 120 degrees (with subcooling) and it doesn't make cold air unless you keep it there. That's why the Condensor is in front and the thermostat is used to control optimum operating coolant temperature. All of the L98's use a pressure sensitive a/c switch to hit the sweet spot for fan operation and the CTS signal is ignored. Try running it without this engineering and you'll blow a hole in the hood, or the charge/pressure will be too cool/low to keep the Low Pressure switch Contacts closed (if the Coolant Fan runs full time) and the compressor will start cycling which shortens it's life. It ain't rocket science - you have to move up to an LT 1 (or later) for that which uses a more precise thermistor type of Sensor which precisely controls the Fans to keep the a/c charge within the desired range of pressure (which is a temperature - allmost 100 degrees below the threshold for fan operation with the a/c off ). They teach this stuff in HS Auto Shop don't they? Well, maybe not the a/c part, but any car running the a/c will run cooler than it will with it off - it has to to keep it together. Oh, it's also exempt from Federal and State Emissions testing. Hate it when I go in on a 100 plus day and they've turned it off and the interior ends up all hot and toasty. Anyway, if yours doesn't work this way, something is wrong - plugged up a/c, air flow, and host of other maladys that can sometimes be quite expensive to repair (like an a/c rebuild: $800 to $2000 - not worth it on a lot of 20 year old wrecks). Anyway, plenty of others have posted the same operating ranges with the a/c on. Try it in your Toyota with a scanner hooked up and you should find the same.

 

Most people on here do not even realize that Gm vehicles have been running these temps sense the 70's. Back in the day of clutch fans the lock up temp for the fans were in the 220 just what our fans turn on at now. This is nothing new or just haveing to do with GM the thing is in most cars we dont have a digital gauge telling us what the temp is. We have gauges with a cold at one end and hot at the other or 100 and 320 or something. Like Sun said run a scan on a lot of cars and you are going to see temps like this.

 

The 89 bin file shows the ECM has programmable on and off fan temps when the AC is on. The bin file shows 226 F for fan on and 221 F for fan off. The temps are based off of the engine CTS sensor.

Assuming the AC system is operating normally, if the AC Coolant Fan Switch were to fail, the radiator fan would come on at 226 F so no hole would be blown in the hood.

It's a piezo electric transducer.

 

Don't know where you got your info though I think Tequila Boy posted it sometime ago - Pin D11 is a/c fan control on the L98 ECM controlled by a pressure sensitive switch which gets a 12 volt reference. It drops to 0 when the switch closes at 230 psi which then drives the Main Fan Relay. This pressure, for R12 is 148 degrees (considerably less with subcooling). It remains closed until 190 psi or 134 degrees (again considerably less with subcooling). What's squirting out the compressor is instantaneous pressure - there's no warm up. Fan is on well below the CTS signal. If it wasn't, pressure would spiral out of control and blow it up long before the thermostat even opened. To maintain what makes cold air, fan cycles on/off far more frequently then with CTS control which is why Coolant Temps are are 8 to 12 degrees less. Tuners seemingly ignore how a/c works and screw it up (or maybe they just don't get it and want to plug in some temperature; but it sure beats me). If it were under control of the CTS, the results could be catastrophic if you were standing over it. The engineers who design these systems know that - so do people who want cold air.

 

And while were on the subject, those converting to R134 face a real problem as the R134 molecule is much smaller and therefore can make some real pressure at ambients above 95 degrees. The OEM's resolved this by turning on the fans at lower pressures - usually 170 to 180 psi - and even adding a second speed to allmost everything with this gas after '95. Relatively speaking, these cars push a ton of air to keep things under control. On the L98, there isn't a Pressure Sensitive switch with a lower parameter so these conversions often lead to higher temps and lukewarm air when it's really hot. It's extremely important to make sure that you lower the weight of the charge on these cars and I think if I did one, I'd probably take a look at what's going on when it's 90 or better and adjust the charge accordingly. This isn't something you can tune for - the parameter is simply a voltage drop on the ECM reference when the switch closes. If you were to try, as suggested, to use Coolant Temp - stand back!