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Coupe is overheating with AC on during 90 degree days

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Old 07-14-2017, 05:06 PM   #1
William Buckley
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Default Coupe is overheating with AC on during 90 degree days

I have an overheating problem with my A6 when in city traffic and the temps are in the 90's. Car is NCRS, and I do not want to have to install an electric radiator fan.

Timing has been checked. Temp overheating is verified by IR gun. Fan shroud is intact, and fan clutch works. New thermostat. A6 compressor has been checked and charged.

Car is factory AC/ 327-300hp/ auto tranny/ 3.36 gearing/ and the AC does no overheat on the highway ..... only stop and go city traffic.

Think that I have covered it all. The car had the same problem with hot summer temps last summer, so I just run the AC on the highway, and sweat in city traffic.
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Old 07-14-2017, 05:15 PM   #2
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Do you have a functioning VAC ( B26) connected to full manifold vacuum? You need about 26* of idle timing to minimize EGT.

Last edited by Donald #31176; 07-14-2017 at 05:17 PM.
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Old 07-14-2017, 05:21 PM   #3
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air flow problem. either fan clutch, radiator, or air flow not coming through radiator.
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Old 07-14-2017, 05:28 PM   #4
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when was the last time the fins were blasted out with a water hose (on both)? Can make a noticeable difference.
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Old 07-14-2017, 06:24 PM   #5
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All factory air cars have a lower radiator shroud extension, upper radiator air dam, and lower radiator seal. Do you have all 3 of these items??

What is the part number of the radiator fan you have, and is it positioned almost entirely inside the fan shroud area??

If the fan clutch is a service replacement, it may be set for an incorrect engagement temperature. Is your fan clutch a later service replacement or an original??

Agree with Donald #31176. Check it out.

Larry

PS: Does your idle engine temperature exceed 220 F (by IR gun)?? If not, I would be happy. If so, how high does it go??

Last edited by Powershift; 07-14-2017 at 06:27 PM.
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Old 07-14-2017, 07:29 PM   #6
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If it's running 220 or so but not puking coolant it's not overheating. Is it spitting out coolant and boiling over? I agree that high temps at idle= not enough airflow through the radiator core. But higher temps at idle are normal with the AC on in traffic on a hot day. Puking coolant is not.
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Old 07-14-2017, 09:54 PM   #7
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You said you had the same problem last summer. Did it ever run cool in traffic before then? Or has it always run hot in traffic?
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Old 07-14-2017, 10:18 PM   #8
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How old is the radiator? My '68 ran 180 all the time, even in traffic, but then a few years ago, it was marginal, and any sitting let it climb to 220 or more. And it would not go back down once I was rolling along the highway with lots of cooling airflow.

I pulled it to have it cleaned and rodded but it was too old and thin to do. I put a new one in and it is back to 180 while sitting in traffic in the summer.

It doesn't matter how much airflow you have, if the radiator won't radiate heat out, the airflow can't take it away.

If the temperature goes up while sitting, and won't go down once moving. Or it goes up while moving, then your radiator is most likely done.

At 60 mph, you shouldn't need a fan at all. If you are overheating at that speed, you have a radiator problem or some blockage in the coolant flow.
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Old 07-15-2017, 02:35 AM   #9
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My mom told me "Back then they all overheated. Why do you think they had those water bags for cars to carry."

Today we have more people on the road and more opportunities to get stuck in traffic than they did 50+ years ago. If you want the convenience of A/C in 2017 traffic conditions you might need to add an electric fan (Spal makes them). I added one to my '62 and no one even knows it's there unless I point it out. I did the opening day parade at the L.A County Fair along with a bunch of C2's last year in the September heat. 5 miles an hour for 30 minutes. The C2 in front of me dropped out half way through with his cooling system puking all over everything. Mine held steady at 179 degrees, fan on.

No evidence of the fan on it, except for the 90 amp Powermaster old school looking alternator with the properly dated "Delco" tag on it. Hint. The 16" Spal puller fan is inside the shroud against the radiator.



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Old 07-15-2017, 02:37 AM   #10
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Quote:
Originally Posted by Procrastination Racing View Post
How old is the radiator? My '68 ran 180 all the time, even in traffic, but then a few years ago, it was marginal, and any sitting let it climb to 220 or more. And it would not go back down once I was rolling along the highway with lots of cooling airflow.

I pulled it to have it cleaned and rodded but it was too old and thin to do. I put a new one in and it is back to 180 while sitting in traffic in the summer.

It doesn't matter how much airflow you have, if the radiator won't radiate heat out, the airflow can't take it away.

If the temperature goes up while sitting, and won't go down once moving. Or it goes up while moving, then your radiator is most likely done.

At 60 mph, you shouldn't need a fan at all. If you are overheating at that speed, you have a radiator problem or some blockage in the coolant flow.
He said it was overheating in city traffic, not at 60 miles per hour.
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Old 07-15-2017, 06:44 AM   #11
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All of the suggestions are useful, sometimes adding a BB fan with more blades and a more aggressive fan clutch (the Hayden 2747 is what I use) and maybe adding the rubber gap flap to better seal the radiator will help.

This piece is for 67 A/C cars but fit all midyears with maybe a big of trimming; Dr Rebuild has the nicest pieces, correctly formed. Make sure to order the installation clips for it too.
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Old 07-15-2017, 09:54 AM   #12
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Quote:
Originally Posted by Randy G. View Post
My mom told me "Back then they all overheated. Why do you think they had those water bags for cars to carry."

Today we have more people on the road and more opportunities to get stuck in traffic than they did 50+ years ago. If you want the convenience of A/C in 2017 traffic conditions you might need to add an electric fan (Spal makes them). I added one to my '62 and no one even knows it's there unless I point it out. I did the opening day parade at the L.A County Fair along with a bunch of C2's last year in the September heat. 5 miles an hour for 30 minutes. The C2 in front of me dropped out half way through with his cooling system puking all over everything. Mine held steady at 179 degrees, fan on.

No evidence of the fan on it, except for the 90 amp Powermaster old school looking alternator with the properly dated "Delco" tag on it. Hint. The 16" Spal puller fan is inside the shroud against the radiator.

Up until the early eighties, most cars, and especially Corvettes had absolutely ZERO extra capacity built into their cooling systems. The temp would begin to climb for the slightest reason. It was common to see cars pulled off to the side of the road in traffic on hot summer days (lots of memories of being stuck in beach traffic on the Southern State Parkway). The trick that often helped was to put the trans in neutral and rev the engine to pull air across the radiator. Of course, if the rad was more than a few years old then that trick didn't help, either.

Last edited by 65tripleblack; 07-15-2017 at 09:56 AM.
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Old 07-15-2017, 10:00 AM   #13
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Quote:
Originally Posted by Frankie the Fink View Post
All of the suggestions are useful, sometimes adding a BB fan with more blades and a more aggressive fan clutch (the Hayden 2747 is what I use) and maybe adding the rubber gap flap to better seal the radiator will help.

This piece is for 67 A/C cars but fit all midyears with maybe a big of trimming; Long Island has the nicest pieces, correctly formed. Make sure to order the installation clips for it too.

OP has a 66 car, so the top radiator seal is a direct fit.........and he should already have it. LICS is a great supplier, but DR REBUILD probably has the best fitting seal(s) for the AC cars.

Larry
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Old 07-15-2017, 10:03 AM   #14
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Quote:
Originally Posted by 65tripleblack View Post

Up until the early eighties, most cars, and especially Corvettes had absolutely ZERO extra capacity built into their cooling systems. The temp would begin to climb for the slightest reason. It was common to see cars pulled off to the side of the road in traffic on hot summer days (lots of memories of being stuck in beach traffic on the Southern State Parkway). The trick that often helped was to put the trans in neutral and rev the engine to pull air across the radiator. Of course, if the rad was more than a few years old then that trick didn't help, either.
But you generally opened all the windows and ran the heater full blast to try and remove the heat (unless Mom or girlfriend was in the car)

Larry
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Old 07-15-2017, 10:11 AM   #15
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Quote:
Originally Posted by Powershift View Post
OP has a 66 car, so the top radiator seal is a direct fit.........and he should already have it. LICS is a great supplier, but DR REBUILD probably has the best fitting seal(s) for the AC cars.

Larry
I mis-typed Larry, Dr Rebuild has the most correctly formed of the seals; I have one that's going on the 63 if I ever have issues (with some trimming around the radiator)...
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Old 07-15-2017, 10:13 AM   #16
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Quote:
Originally Posted by Powershift View Post
But you generally opened all the windows and ran the heater full blast to try and remove the heat (unless Mom or girlfriend was in the car)

Larry
....................which brings up a funny story of me and 3 buds who went cross country in a dilapidated jalopy of a '75 Dodge MaxiVan in 1981. We were near Badwater, in Death Valley in 120 degree heat and the Dodge temp started climbing fast. I pulled off the engine cover, opened all the windows, heater full blast. The temp stabilized but one of my buds suffered. You see, I had broken his nose a week earlier while horsing around and we all wore those old Groucho Marx eyeglasses with the moustache heavy eyebrows and BIG plastic nose...except my bud with the busted nose. His nose swelled to twice the normal size and turned red in the heat. We all had another beer or three, had some laughs and kept driving.
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Old 07-15-2017, 12:52 PM   #17
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Quote:
Originally Posted by Randy G. View Post
He said it was overheating in city traffic, not at 60 miles per hour.
You are taking it out of context. If you don't include the sentence above, it means nothing.

Quote:
If the temperature goes up while sitting, and won't go down once moving. Or it goes up while moving, then your radiator is most likely done.

At 60 mph, you shouldn't need a fan at all. If you are overheating at that speed, you have a radiator problem or some blockage in the coolant flow.

If it overheats sitting, and then it stays overheating once back up to highway speeds, then the radiator is not radiating heat. Because at 60 mph, you don't even need a fan for the radiator to get rid of heat. This is an important factor to know if it is the radiator or not. Some bad radiators will stay marginally cool as long as you are running at speed but stop in traffic, and they overheat and won't ever resume a cool condition when moving.

The other issue would be a thermostat that isn't opening. It sips enough for being at speed, but not enough sitting. And then when moving again, it won't let enough pass to cool back down.





Back to the OP, once it overheats in traffic, does it go back down once moving?

If it doesn't, then the radiator isn't getting rid of heat and needs replacing.

If the temperature goes back down once moving, then you have issues removing heat sitting. this includes:

1. not pulling all air through the radiator
2. air flow blockage
3. hot air polling in the engine compartment
4. water flow too low
5. coolant mixture wrong


Too many air gaps around the radiator and core support.

Air blockage in fins of AC condenser or radiator

Air is trapped in engine compartment due to side louvers blocked, sidepipes added holding heat under car, etc.

Wrogn pulley on the water pump or on the crank, running the water pump at the wrong speed. Or it could be the water pump isn't any good.

Pure water in an AC car won't transfer enough heat.
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Old 07-15-2017, 01:27 PM   #18
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The Desert Cooler burlap water bags were common in the days of non-pressurized cooling systems that boiled over at 212 degrees. The 1950's saw the introduction of more modern pressurized cooling systems. Hell, my 1915 Ford is pressurized: it has no water pump at all. Has Thermosyphon cooling, works like an old percolator! The OP still hasn't explained if his car is really overheating.....(puking/losing coolant and getting HOT). So far I take it that it runs hotter on 90 degree days with the AC on in traffic than at other times. Pretty much a normal occurrence.
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Old 07-15-2017, 01:30 PM   #19
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Quote:
Originally Posted by 65tripleblack View Post

Up until the early eighties, most cars, and especially Corvettes had absolutely ZERO extra capacity built into their cooling systems. The temp would begin to climb for the slightest reason. It was common to see cars pulled off to the side of the road in traffic on hot summer days (lots of memories of being stuck in beach traffic on the Southern State Parkway). The trick that often helped was to put the trans in neutral and rev the engine to pull air across the radiator. Of course, if the rad was more than a few years old then that trick didn't help, either.
The early 60's cars without A/C (which was most back then) had plain 4 blade fans, no shroud, no overflow tank ect and idiot lights. I did a lot of NY driving in the summer bridge and tunnel traffic in those cars back then and it was common to see overheated cars on the side of the road. By the time the light came on you were already in trouble in traffic, sometimes with no place to pull over.

Fortunately, these days we have some nice options for our older Vettes like new aluminum Dewitts radiators to retro fit, and additional cooling fans which cured my Corvette issues.

OP : Depending on how old your radiator is, I would start there, they can easily loose capacity through corrosion and age which is the difference in high demand cooling situations (A/C in traffic)
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Old 07-15-2017, 02:55 PM   #20
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Are you sure the fan clutch is working properly?

Seen a lot of people who do not understand their working purpose.

Fan clutch is designed to slip under hard acceleration, not under normal acceleration. You should feel resistance when you try to spin it with your hand. If you can turn it easily with you hand it needs to be replaced as it's slipping under normal low speed driving, when it should not, thus causing over heating.

Just went through this with a friend who's El Camino was overheating driving around town, he thought it should be easy to spin thus he thought it was good.
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