I’ve had or 74 E since new; wondering if i replace the original radiator with aluminum and use the high efficiency coolant, can i get my car to run cooler in the summer , where Im not constantly worried about overheating when driving in the city/ maybe be able to use the AC?

 

I did have the OE radiator recored in 1992. That lasted until about 2019 and I made the move to a Cool cat radiator along with the Coolcat fans
https://www.coolcatcorp.com/Merchant5/merchant.mvc?
Make sure your coolant hoses are new, as 'flaps' of old hose can impede coolant flow. Thermostat correct?
AC on Es is weak. Your AC parts may be problematic. If it's too hot to drive then the car stays inside. IMO.

 

Thx for your input .. I’ll check that radiator out

 

The key concern in a V12 is that the thermostats are functioning correctly. If you haven't changed them recently, give that a try first. I have no idea what you mean by "high efficiency coolant". All coolants are a combination of glycol and water. The best bet for driving is a 50/50 mix of ethlyene glycol and water, my favorite is Zerex G05. You can add a bottle or two of water wetter, which will give a slight incremental improvement in heat transfer. E-Types have poor air flow, due to the long nose and crowded engine bay. So you need to make sure your fans are working well and the radiator fins are clear of debris.

An original radiator is going to have deposits, some you can remove with flushing, but most not. After fifty years, a new radiator or recore is probably in order.

 

One thing I forgot to mention: With a V12, there's a lot of heat around the distributor. You should check your distributor for free action of the advance mechanism. If the weights stick, your timing will be retarded off idle.

 

I’ll assume everything is working as it should. Coolant changed every 2 years. Hoses every 5. ( with silicone you can go 10) correct thermostat in place.
But when is the last time the distributor was oiled?
If not properly oiled the advance weights freeze up and the timing is off ( which causes overheating).
You won’t feel it because of the power and torque of that smooth running V-12.
If you are a DIY. Guy remove the distributor cap and twist the the rotor to the stop. Let go, If it snaps back quickly and smoothly. Just go ahead and put a few drops of oil down the shaft. That’s not a problem.
If you have a shop or dealer do your work just ask them to check the timing & advance through the revs.
Just for information the stock system was designed to operate properly through hot summer days.
Yes the needle will go up. Past the middle. That is normal and nothing to worry about.
the only point to worry is if the coolant starts to boil. That’s when there is trouble. That occurs in the 125 degree area.
I know there aren’t numbers on the temp guage.
You have to buy one of those digital infrared hand held temp gauges and aim the red dot at the back cylinders coolant tube. ( down by the carburators near the firewall )

 

I had the engine bay on my '74 series 3 apart to convert to EFI. While the radiator was out I cleaned up the fan shroud. There are these rubber fabric flaps on the back of the shroud that puzzled me. I looked into it a bit and found that they are quite important in cooling at speed and and low speeds or at a stop. The deal is that when one is pounding down the road there is a lot of ram air passing thru the radiator, more than can be exhausted by the fans or thru the fan opening in the shroud. Air is backed up behind the radiator impeding flow. The flaps open from the slight increase in air pressure to allow addition air flow thru the radiator core. But when the car is in traffic, the fan is doing all the work. The fan is sucking air thru the core, and every bit it can pull thru the core is needed. The slightly lower pressure behind the core pulls the flaps closed to allow maximum air flow thru the core with no other opportunities for air to pass.
So... if the material of the flaps is hardened, or torn or otherwise compromised (missing?) the air flow thru the core is also compromised in both pounding the road and stalled in traffic. Once I had clarity on this bit, I replaced the flaps on mine with a rubber material that will flex as required. I had something on hand so I didn't bother with checking if replacement is available from the various parts sources.
I'm in Oregon, not known for blazing summers, more for wet all year. It doesn't come up much, but I don't recall cooling problems even when I had the need to use the air conditioner.

 

Although I hadn’t known about the two flaps you describe, I checked out my vehicle and they are in fact In place and in good condition .. when i think of the engineering aspect of these things, it is fascinating to me how these two simple features function in a fairly complex overall system ..

 

The one most important feature to check regarding cooling is that the fitted thermostats open sufficiently so as to fully block off the bypass and thus route 100% of the water to the radiator, rather than just a proportion of the flow. Without this happening, you never harness 100% of the total cooling capacity of the system and so will mistakenly look elsewhere for a solution first. The critical distance is that the thermostat must open out at least 42mm - this lets the spring loaded foot on the bottom land on the bypass port and thus ensures 100% of the water is directed to the radiator. The bypass route to the radiator is much shorter and an easier option for the water to take and simply recirculates hot water back into the block, so even a small proportion of this is going to be unwelcome once cooling becomes critical. The topic of thermostats is covered in plenty of detail on the jag-lovers.com forum if you require further background reading.

Three other lines of attack are:-
1/ open up the heater matrix and thus allow some flow over an additional "radiator";
2/ fit a bypass switch for the Otter switch and engage it whenever stationary;
3/ don't pull up too closely to the car in front if stuck in traffic. This means your radiator is pulling in hot exhaust gasses from the car in front and little if no effective cooling is going to be achieved this way.

kind regards
Marek