I recently just replaced my a/c and when I'm idling or going slow with the a/c on, my car overheats and the a/c isn't very cold. I've been reading some other posts on here, trying to solve the problem but haven't had any luck. I live in Texas and work in a chemical plant where the speed limit is between 5 and 15 MPH, so I'm driving slow alot and I just spent around $700 on all the a/c stuff. I also added a 14" pusher fan to the front of the new condensor to try to help, but nothing. If I turn the a/c off, the temp will drop back down. When idling or driving slow, the vent temp is 70 and when I'm on the freeway it get to around 40. When I leave work and security checks under the hood, the overflow tank is boiling. I thought for sure with the fan on the condensor, it would be colder than 70 and help with the overheating. The radiator is about a year old. Some spec's on the car are..........

91 RS
305
automatic
single fan setup

Any help in what direction I should go or where to start would be greatly appreciated.

 

I was just feeling sorry for you because no one has replied to you yet. I`m not up on air conditioning systems, I`ve got to replace my air before next summer, it`s still the R-12 system and makes so much noise I stopped using it. My suggestions about your running hot are to check your thermostat and fan switch, make sure they are working. Since you are running a single fan you might want to change over to a dual fan set up with a shroud. Puller fans on these cars are the only way to go, pushers won`t work well at all. Also, check the area between the radiator and condenser, it can become clogged with leaves,dead critters etc. I am just finishing up installing a dual fan shroud from a 4th gen LT1 and I will let you know how it works.

 

Thanks for the reply! I know alot of people have wrote about this problem and I haven't heard of anyone actually fixing it. My 88 IROC has the dual fan set up with no ac and a 450hp small block and the temp stays at 180-190. Both of my 91's have the single fan set up. I'm looking around for dual fan set up right now. Do you have to do alot of modification to get the dual fans from and LT1 or LS1 to fit?? Do you know how much CFM the stock dual fan set up is? Thanks again!

 

Both of your symptoms could indicate lack of airflow across the coils and radiator. First thing I'd check would be operation of the stock fan when the A/C is on.

If your radiator or condenser coils are clogged with dirt/trash it can block air flow as well. Pull your top radiator mount off and check between the rad and coils like jimdutro pointed out.

 

Yeah... What he said!

I was gonna post the same thing but he posted it first.

If the AC and the car run cooler when the car is moving at high speed, then that tells me that the fan is not running when you turn the AC on. I would check that first. If it isnt running, break out the schematic and start tracing!

 

Sorry to jump in here fellas but the LT1 dual fan set up intrigues me.I heard that wouldn't work because of the different angle the radiator mount position has between the two.I've had both Lt1 and now have 1992.Too many years in between to remember if there is a difference.I would REALLY like to know if it is possible.I would grab up on that system in a heart beat.Those fans did the trick in Hotlanta when I owned the 1994 Z.

 

385thumper, don`t ever be sorry to jump in, the more input the better. My only complaint with using the LT1 dual fan shroud in my `88 Iroc was the amount of trimming and "fine tuning" it needed to fit flush against the radiator core. Check out the post from 'firebirdjones' on 8-22-06 titled "installed LS-1 fan assembly in my 3rd gen". The LS1 shroud looks much easier to install and looks factory to me and I think it works better than my set up. I`ve just road tested mine today for the first time and the temps stayed below 200 but it has cooled down 30 degrees here since last week. I think the key to using the 4th gen shroud is to also use the factory fans, don`t know, not sure.

 

#1 Is your air dam in place below the radiator? There is no grille on your Camaro. What looks like a grille is actually solid and allows virtually no air flow. All of the air going to the radiator comes from underneath the front end up into the radiator. The plastic air dam acts as a deflector to direct airflow up in front of the radiator.

#2 Was your thermostat & radiator cap replaced with the radiator? The normal operating temp of your engine is 190-220 degrees. If the radiator cap does not maintain enough pressure on the system, the coolant will boil at normal operating temps.

#3 Did you have the engine block flushed out when the new radiator was installed? You could have corrosion build up in the water passages in the block and head that are limiting the cooling ability of the coolant.

#4 Is your fan turning the correct direction? I think under normal conditions with the stock plug the fan will be wired correctly, but if someone cut out the plug and wired the fan directly to the harness, they might have reversed the wires which would cause the fan to run backward. If your fan is running the wrong way and the secondary fan you installed in front of the radiator is running correctly, the 2 fans will cancel each other out.

#5 How is your water pump? Run your engine enough to get it warm enough to open your thermostat, but still stay below boiling. Now with the engine idling, carefully remove the radiator cap and look in to see if water is circulating in the radiator. If you don't see the water being circulated, you may have a bad water pump.

The above responses are what I can think of "off the top of my head" to check out the cooling system.

Your a/c problem sounds like an airflow problem. If you don't have adequate airflow over the condenser coil, your discharge pressure will go up. As the pressure goes up so does the discharge temperature. I think there is a temp switch on the compressor that will open and shut off the clutch if the temp goes too high. If your air dam is in place, your fan is working correctly, and you have no debris plugging your radiator/condenser coil to stop the airflow, your a/c should work fine. I almost forgot to mention, check to make sure your fan comes on anytime the a/c is operating. You have a fan relay on the firewall that turns on your fan anytime the a/c is turned on regardless of engine temp.

I hope this helps you figure it out.

 

Russ, thanks for helping to shake some cobwebs out of my head. After installing 2 new fans in my `88 Iroc with a 4th gen shroud, I got about 3 miles from home and my temps hit 250. I hooked up everything correctly, the wires on the fans were reversed. Moral of this story, verify that your fans are pulling correctly. Your #4!

 

I put the dual 11" fans from spal on, a/c blows cold and car doesn't overheat. I highly reccomend these fans. Found them new on ebay for $207 shipped!!

 

i had the same problem when driving around that speed. The problem I had was that my radiator was rusted on the inside and old. The most interesting part was that i had a friggin family of LARGE dragonflies and various other bugs in my cooling system causing a blockage. I found them when i decided to drain my radiator. There was All types of nastyness comin out of there.
i bought my car out of nashville tenn.

I corrected my cooling by:
pull your lower hose and drain. Refill with prestone. Hypertech t-stat and switch. autozone new raidiator and hose.

NO MORE problems. I also yanked the a/c. I couldnt stand the ugly setup. It never blew ice cold and it had a fowl smell to it.

The 91 works like a million bucks!