ok, its 95 degrees and humid all week, ive ran the ac on max all the time, and i see about 220 degrees temp while idling and a little less while cruising. fine. well, the other night i idled it for five minutes and i went back in the car and the temp was trickling on the edge of the red (245-250 degrees) and as i drove around it WOULD NOT come down AT ALL even while cruising at decent speeds without stopping-until i turned off the ac and she plummeted down to between 160-200 while idling/cruising. i have a flushed cooling system with new coolant, 160 degree stat, good water pump, both good hoses, good radiator, new radiator cap, good air dam, everything, but for some reason the other night the temp just soared. why?

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soon that white 5.0 lx at school will get a good waxing from a nasty 355 RS...heheheheheh

 

Have you checked the fan operation with the A/C on and off, just a thought of a place to start.

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Rob
'86 TA 305 TPI
Gutted MAF, Ported Plenum
TB Bypass, Home made Cold Air Intake,
Edelbrock T.E.S.

 

Same here. When I crank on the a/c the temp creeps slowly past 220. Although, it hasn't reached 240/50. If I turn off the a/c, then the temp goes back down to 220. Before, when the a/c was on, the temp would actually drop to the mark between 100 and 220. My fan is running fine. Coolant level is good. I'm puzzled...

 

Same here also Guys! In Florida here it gets pretty hot & Humid, with the air off the car stays around 170-185 cruising or highway. But if I put the air on the temp goes to 220 - 230. I have installed a 170 thermostat, and a hypertch fan switch. And both my fans are working with the air on. I give up on this. As long as mine stays away from the red I guess I will live.
Good luck guys.
Mike

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(Gran Turismo Americano) "The Ultimate Firebird"
Smokin 1989 GTA- Bone stock except for exhaust. (no catalytic-stainless pipe into Flowmaster 2 chamber).

 

damn, me too, with ac on around 235-240, turn it off, back to 220,

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1986 TPI 305 TRANS AM

 

I don't know if this is something that we just have to live with when our cars get older or what. I've got a 1985 IROC-Z with 122K on it and like most everywhere else, it's been really hot and humid here. i took it on a 4-5 hour trip the other day and ran the A/C on max the whole way. The temperature gauge was fine while cruising at 65 to 70. It would creep up just below the mark above 220 when in stop and go traffic. Got on the interstate running 75 for 16 to 20 miles and it was flirting with the red. Well that was three days ago. Yesterday and today, while driving around town in stop and go traffic, it was in the red. My mechanic has checked everything and cannot find a reason for it to be running that hot. I know my fans working and turning on at the right temp, got the right thermostat and the radiator and motors been flushed. I'll just keep driving till it gives up on me.

 

One thing that it could be is dirt or garbage in between the condenser and the radiator. I had the same problem last year and found this space to be 3/4 of it full of dirt and leaves. Might not be your problem but it doesn't hurt to check.

Steve

 

Any of you notice a theme here? Everyone of you have said that your car is running at or around 220*. That is normal operating temp for our cars. The ECM is programed to kick the primary fan (if you have dual fans) on at or around 228* and the only way that I personally know of is to get a custom prom to have the fan kick on at an earlier temp. The second fan is only for the A/C or is the car gets around 240*.
To 302Killer I would check to see if your primary fan is coming on at all. If it is not one thing to check would be the CTS it should only cost around $15-$20 for a new one and is not that hard to change. That was my problem the other week. I could not get my temp to stay down for some reason and it came to be my CTS and now I am running just right.

 

i forgot to say i checked my fan the other night when it was in the red and it was on and functioning

 

Not disagreeing they run (too??) hot. Why put a 195 F thermostat in a system that can't run 195 F?? - except when it's cold outside. In order for the coolant to keep the engine cool, it has to be below the 195 F temp of the thermostat, or the thermostat stays wide open, the engine runs variable temperatures (controlled by outside air, engine load, car speed, etc.) because the system is not designed to control temps at a set temp. (like my 81Z and every other vehicle I own except the 83Z and the 86 IROC) Sorry, probably the only pet peeve I have against these cars (except for that narrow bucket seat).

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Z's r Best

 

I had a problem a while back where the temperature was reading hot sometimes and it wouldn't come back down. Here's what I learned. CHECK TO MAKE SURE THE GAUGE IS RIGHT!! I replaced the fan switch and almost the fan, and almost the radiator (I finally put in a 3 core since the side tank went anyways) before I found out that the gauge was reading wrong. It was the weirdest thing, it also had a mechanic fooled (though he wasn't that good).

Good luck either way, the temps your running are killing your cars if the gauges aren't acting up.

Mike

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1989 RS.. 355, Hypereutectic pistons, double roller cam, double roller timing chain, accel wires, blue streak cap and rotor, rapidfire plugs, chevy caprice 350 chip, 200* fan switch, 3 angle valve job, 3 inch cat-back exhaust, 3 core radiator, 3.73 gearing with POSI.

 

Desert86Roc pointed out that he was missing his A/C condensor seal. And realistically most of us probably are. The adhesive dries up and they blow out. This allows a portion of the air to flow "past" the radiator and condensor. For about 3 bucks he was able to repair this which did two things:

Lowered Op Temp
Improved efficiency of his A/C.

I'm not saying that this will solve more serious op temp situations BUT every degree of reduced temp HELPS.

http://www.gmtips.com/3rd-degree/

Enter Site
Choose Tips
Choose A/C Condensor Seal Article

...if you want to check this possibility.

 

jeezus...and i thought my 454 mainting 200 on extremely hot days was bad. I'm not worried now with all these sbc's running this hot!


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85 Berlinetta Iroc exterior NOW 454 powered, 4.10 gears, 275/60/15 Hoosier Quicktimes and a PILE of other goodies..........YES, it's street driven!

check it out at http://www.bsronline.net/members/rob/rob_specs.html

 

my A/C is chilling cold so i dont think i blew out a seal because i do start it time to time in the wintwr and fire up the ac. it is just weird because it only happened once where it went red but normally runs about 220 which is normal

 

Well I can explain why the A/C raises the temp of the car when it is on and maybe why these cars are running too hot.

First off, it is normal for the car to run hotter when the A/C is on. The A/C system removes heat and humidity from the air. It does this by compressing refrigerant (R12 or R134a) to raise it's boiling point with the A/C Compressor, and then blowing the air that is going into the car over a heater core like componant that is called an Evaporator Core that contains this high pressure refrigerant. This basically absorbs the heat from the air as it flows across the fins of the Evaperator Core. The humidity is removed from the incoming air at this point as well due to the drop in temperature of the air as it flows across the Evaperator Core. The water in the air condenses on the Evaperator Core and than drips down through the heater case onto the ground (that is where the water that drips onto the ground near the front of the passenger door area comes from when the A/C is on). The high pressure refrigerant is then fed to to the front of the car to the Condensor, which is the piece that is mounted in front of the radiator, via the Compressor. The refrigerant is allowed to boil in the condensor by dropping the pressure to the point where the refrigerant will boil. A componant called an Orifice Tube, along with the Compressor itself, seperates the A/C system into a low pressure side and a high pressure side. When the refrigerant boils in the Condensor, it releases the heat that it absorbed in the Evaperator Core. This is where the heat exchange takes place. The heat that the Condensor releases from the boiling of the refrigerant flows right into the radiator and back into the engine bay which is why the engine runs hotter when the A/C is on. The Condensor needs air to flow across the it's fins to facilitate this heat transfer which is why the car has a fan that comes on when A/C is requested.

I don't know if I explained that very well, but you get the idea. The Condensor gets hot when the A/C is on which is why the car will run hotter. The A/C system needs airflow to operate efficiently which is why one of the fans comes on when the A/C is requested. This is also why the A/C system blows cooler air when you are going down the road vs. when you are stationary, more airflow = better heat exchange = cooler air from the vents.

So that will explain why the engine runs hotter with A/C, but the car should still stay away from the red area on the guage. I would suggest that all of you get out the garden hose when the engine is cooled down, and run some water through the fins of the radiator and the Condensor. F-bodies get all of their air for cooling purposes from off the air dam which basically sucks up all of the dirt and debris that is laying around on the road. The radiators and condensors on our cars get filled with $hit in a hurry . Cleaning out the radiator and/or condensor is an absolute must for our cars (not a bad idea for every car really). You will be amazed at how much $hit will be lodged in the cooling fins of the radiator and condensor.

This operation is most easily done by first doing a visual inspection form above and below the car for any large pieces of debris. Than remove the air intake system. Then unbolt the black plastic radiator shroud and pull the fans rearward, allowing access to the radiator. Then run some water through the radiator from the back towards the front at a reasonable amount of pressure. After the radiator is clean, you can tip it back a bit and hose out the condensor as well. Make sure the car is cooled down before doing this as the water from the hose will be fairly cold and could damage a hot radiator or condensor due to an acute temperature change.

After the radiator and condensor are cleaned out, your car should run a bit cooler and the A/C should operate more efficiently.

I have seen large items such as trash bags, full sports sections, and cardboard boxes get lodged up in the radiator before so don't be surprised if your car runs A LOT cooler after doing this .

Good Luck All......



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1987 GTA L98 MD8 GH3
355 '97 Vortec 4-bolt block, TRW(suck) forged pistons 10:1 CR, TFS 23*, LT4 Hot Cam, Ported plenum and intake, SLP Siam Runners, Edelbrock TES, gutted Cat, Flowmaster, K+N cone, AFPR, TB bypass, AirFoil, !AIR, !A/C, !EVAP, ARAP, 2300 stall, Hotchkis STB.