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Stock 318 runs 30 degrees hotter with AC on- is this normal?

YY1

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Last year I put in a mechanical temp gauge (factory gauge was horribly off calibration).

It runs at 165-170 degrees.

I know, but I checked it against an infrared thermometer and it was within 2 degrees.

So anyway, If I run the AC (all stock RV-2 but with 134a professional conversion), it gets up to 190-195 and when I shut it off the catch can overflows.

I like to keep about a pint of coolant in the can which is about 1/2 the quart capacity.

I don't remember it doing this before, but until last year I didn't have a good temp awareness.

If I don't run the AC, it doesn't seem to ever get above 170, even in the 95 plus degree FL spring and at 65-70 MPH highway speeds.

Is my compressor giving it up?
 
I dont know if its giving up the ghost but the RV-2 dual piston compressors are very inefficient. I had one on a 79 warlock with a 360 and had similar experience where is ran about 20deg higher with AC on here in TX. I had planned on converting to one of the newer scroll type compressors that came on the 80,s Diplomats. They mount in the same location but require different hose ends. I've had a few 318 Dippys with 200K+ over the yrs and never had cooling issues running the AC with the scroll compressor.
 
Because of the desert heat,I run a coolant conditioner that helps. I usually don't believe in snake oil products.I run HyperLube coolant additive.I works for me. It maybe the change from R-12 to R-134.( don't know the science behind them) I did the changeover in my 88 D350. I now run a electric fan in addition to the mechanical ONLY while the A/C is on. That really helped with both engine temps and the cabin.
Just a thought.
 
Are you saying your overflow bottle is only 1 quart capacity? Just curious, because in 73 some cars came with overflow bottle that were 3 quart capacity, mine is that capacity. Also, just an FYI, I keep about 1/2 quart of coolant in mine, and when it gets really hot, it can fill up as much as 1 to 1.25 quarts of coolant into the overflow tank. When it cools, it sucks the coolant back into the system.

I am also using stock AC with RV-2 converted to 134a, and I haven't really noticed a temp increase, but I am running the recommended thermostat, 195 in my 340. Do you have the correctly rated thermostat installed?
 
Are you running a stock non clutch fan? What size radiator does the car have?
 
195 not so bad in your brutal heat. Leaving 2” to top of radiator? You do have sea level going for you. Mine won’t run over 178 today with ac. 72 ambient. Defective clutch fans hard to diagnose if you have one.
 
Just me but if the radiator is burping coolant at 190/195 after shut down I would stick a new 16lb cap on it, and like Dennis said leave a little room on top.
 
Aproperly functioning "coolant recovery " system assures that there is never any room at the top. The system should always be full or something is not working properly like a defective or incorrect radiator cap. And 170 ° is too low for proper economy/fuel burn. The factory has always recommended 190 ° thermostat standard. It needs to run hot, just not too hot. Remember that the cooling system needs to be pressurized to function properly. This is why the water does not boil at 212 ° in a pressure cooker. If the system does not hold pressure it will over heat at a much lower temp.
 
I'm fairly certain the thermostat is a 180.

The car had no recovery jug, which I though was odd on an AC car.

I made one from a translucent, graduated travel mug. That's why it's only a quart.
It works fine, and coolant flows in and out as necessary except when running the AC for extended periods. I use the normal setting and not max so the compressor cycles.

26" radiator. Fixed fan which I also thought was odd for an AC car.
 
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Not really odd for an non-ac car to have a standard fan. This is listed in 73 for 318 with a 26" radiator with AC. The two fan options are a 5 blade 18.5 inch fan or if you have 2.94 or 3.23 axle ratio there is a 18.5 inch 7 blade fan that uses thermal drive. Now, if you have a standard 4 blade fan, that is incorrect, those were only used on non-AC cars.
 
That sounds about right. My Coronet runs a good 20 degrees hotter and will climb over 210 sitting in traffic with the AC on in the 105 degree desert 12 noon sun. Shut of the AC and it immediately drops 15/20 degrees once it gets some air across the radiator moving. It is 100% original stock or NOS parts. I don't drive it in town during the summer anymore.
 
So what is the normal fluctuation in coolant to go from the rad to the overflow jug?

Could it be that I simply need to get a larger jug?

If the normal volume is over a pint.....

I try to keep my 1 qt jug about half full and have been checking and adjusting before every drive.
 
So what is the normal fluctuation in coolant to go from the rad to the overflow jug?

Could it be that I simply need to get a larger jug?

If the normal volume is over a pint.....

I try to keep my 1 qt jug about half full and have been checking and adjusting before every drive.

'68 just goes on the ground. I keep it about 1" or so down in the radiator
 
The scroll compressor is not used in automotive applications. Perhaps the person that noted this meant to say "Sandun" axial flow compressor. This is similar to the old GM Delco A6 6 cylinder compressor. The efficiency of the old RV-2 was adequate when using R12 refrigerant. When the system is converted to R134A, the pumping capacity is slightly increased due to the higher density of R134A as the specific heat (refrigerant's ability to absorb and release heat) characteristics is greater. Likewise, the condenser efficiency allows for higher heat rejection into the cooling air to the car's radiator....trying to cool hot water with hotter air due to more reject heat ftom the condensor, causing a higher coolant temperature. A system designed to operate on R134A has both evaporator and condenser heat exchangers with more fins / inch than those designed to operate on R12. The R134A operating system pressures are also higher than the old R12 which also adds to the heat load. Higher air flow across the condenser and subsequently thru the radiator will definitely help the engine run cooler and also increase the efficiency of the condenser. Remember, a refrigerant system does not make cold it simply removes heat thru the process of "latent heat of vaporization"......
Bob Renton
 
Can't speak to the effect on the radiator but as far as cooling capability in the cabin, the 134 in the RV2 system does just fine.
 
YY1, wanted to ask you a question about your AC setup, but your inbox is full.
 
Update-

I found a $5 48oz water jug (catch can) at wal-mart and swapped that for the 32oz I was using.

This allows 24oz of coolant as reserve with a 24oz overflow rather than 16oz.

It still gets 30* hotter with the AC on but so far has not overflowed the catch can.
 
My 318 Swinger with dealer installed Airtemp air runs much hotter with it on. It has blown coolant out on a few occasions. It still have the stock 19" radiator. :BangHead::BangHead:

I did add a clutch fan which helped and Bob @ Glen Ray is building me a 22" radiator that I can add a shroud to.
 
Gentlemen,
A curiosity question....where do you think the absorbed heat from the passenger compartment is going? The heat of compression generated by the AC compressor is added to the heat absorbed by the evaporator and is rejected by the condenser into the air stream going into the engine's coolent radiator. You now are trying to cool hot water (180°-200° F ) with 140°-150° F air. The net result is the the engine's coolant will be hotter. The greater the temperature difference between the two cooling media the more heat is exchanged. Its not a total function of coolant type (water, propylene glycol, ethylene glycol, Evans coolant, water wetter surfactants, etc) but system pressure, system circulating velocities and quantities (gallons per minute), and heat exchanger surface area. The laws of Thermodynamics applies. Just my opinion of course.
Bob Renton
 
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