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How to Install ebay L20B Aluminum Radiator (710)


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So I wanted to post a How to / Information thread on installing one of those thick 3core ebay radiators that "fit" our Datsuns. I was suffering from overheating issues on my 710 from a clogged radiator so I was in the market for an "upgrade".

I paid $180 for the radiator and a 16" electric fan kit. My hope was that it would fit the standard holes in the body and all I would need to do was hook up the radiator hoses and wire the fan but it turned out to be a much bigger project.


In all I purchased

L20B radiator (ebay) (16" fan didnt work for me)

12" Diameter High Performance fan (amazon)

Small Automatic transmission cooler (ebay)

Derale 16738 Single Stage Thermostat push-in probe (ebay)

Some wiring and electrical tidbits

Hardware for mounting the radiator


After removing the stock radiator, this is what you are left with. To remove the radiator, take off the front grill and the nuts that hold the radiator in place are easily accessible. If you have an automatic, you need to pull the transmission cooler lines off from the bottom of the radiator. If you plan on wiring an electric fan (you need to for this radiator) the fan clutch shown has to be removed but it cannot be unbolted from the water pump. To do remove the fan clutch, you need to unbolt the water pump from the engine and cut the shaft right between the clutch and the belt pulley. I don't have pictures on this process but you will see what it looks like finished in later photos.



With the fan clutch removed, the water pump can be reinstalled.

Carefully sit the radiator in place. When I did it, it became clear that it wasn't a simple "bolt-on". The radiator did not have the proper width to match the bolt spacing. Also it was really thick so fitting it without damaging the fins was difficult. I also found it was really difficult to position it without hitting the alternator pulley.

20170414_182550.jpg 20170414_182538.jpg


Due to the lower radiator outlet and the alternator pulley, you want the radiator sitting as far over to the passenger side as possible. On the passenger side, the radiator should practically be able to bolt up to the standard holes. I think I had to add a 5/16" hole to the upper aluminum bracket on the radiator to allow better fitment. On the drivers side, I made an adapter plate out of 1/8" aluminum that would allow me to bolt the radiator up to the body on the drivers side. The plate sandwiches the body of the radiator opening between the plate and the radiator bracket.


710_radiator_bracket.jpg 20170727_182128.jpg 20170423_160121.jpg

Make sure that any place the radiator may rub the metal body of your car, you add some type of padding to prevent future problems. I used a piece of thick rubber vacuum line that i sliced into to fit around the body nice and snug. You can see it right behind the lower bolt head.


At this point, the radiator should be mounted. You can see what the water pump pulley looks like all cleaned up with the clutch removed. Note the relay installed on the passenger side of the radiator and the thermostat probe directly under the upper radiator hose. You want the probe right under the upper radiator hose so you can have the quickest cooling response when your engine reaches temperature. The relay was mounted on one of the brackets provided with the radiator.

With the fan clutch removed, I still didn't have enough much room for my electric fan.


As I mentioned before, the lower radiator hose is dangerously close to the alternator pulley. I had to buy a fresh alternator belt that was unstretched so that I could take advantage of any adjustability left in the alternator bracket.


To fit the electric fan, I had to install it in front of the radiator. The fan needs to have the capability to be wired as a pusher in this configuration. Using the 16" fan provided with the radiator, I was able to make it fit, but I was unhappy with how it sealed against the radiator. The 16" fan was just big enough that it could be persuaded to fit in the stock radiator opening but it caused the 3 and 9 oclock position of the fan to lift off of the radiator which made it inefficient. The other thing I noticed was that the blades had a good 1/2" clearance around the entire circumference of the fan shroud. Because the radiator is so thick, when I tested the fan, I could feel a lot of air being pushed through these openings and not actually making its way through the radiator.  I ended up finding a 12" fan with large fins on amazon. Even though it was smaller, it was able to force much more air through the radiator because it sealed better.


Here is the 12" fan. The black heat exchanger you see in the top right corner is my automatic transmission cooler.


Wiring the fan is pretty straight forward. I bought a "Derale 16738 Single Stage Thermostat push-in probe" on ebay. As I mentioned before, the probe should be installed as close to the radiator inlet as possible. This will give it the quickest response based on your engines heat. Make sure where ever you put it, it does not push into the radiator fan or you'll have some trouble.  I installed the relay on the radiator close to the battery to try to keep wiring clean and simple.


In the photo below, wiring is as follows

Black(on relay): ground

Red: Straight to battery

Yellow:Thermostat probe

Green: On/Off Switch (if you want to be able to bypass the thermostat probe) or you can delete it.


Orange through Inline fuse (provided with relay) to black wire on electric fan( because we are wiring it as a pusher)

Blue/Red (power) on electric fan gets wired to ground


Brown (what ever color you choose) will be your power signal to your thermostat probe. I spliced into the blue/red wire at the wiper motor.This allows the fan to run only when the car is on and the thermostat reads above its set temperature, but it will not run while you are trying to crank the engine over even if the radiator is hot. The other side of the brown wire goes to the thermostat probe.





Here it is all back together. Everything fits as best as I could get it and it's looking nice and pretty. Usually when driving, the electric fan doesn't turn on. The temperature gauge in the car reads about 1/4-1/2 way mark. Its about 1/4" above the lower operating range tick. As it moves up to around 1/2 way mark, the fan kicks on. Mostly this only happens when the car is idling in traffic. Then it cools back down and the fan shuts off. I wired an on/off switch in the engine bay that bypasses the thermostat using the green wire. When I turn the switch on, even without the key in the ignition, the fan runs. I figured this would be good if I pull over to the side of the road for some reason and pop the hood and want to run the fan without wasting power on anything else. 

If I had to buy another radiator, I'd probably go another route because of the clearance issues between the alternator and the lower radiator hose. Im pretty sure all of the ones offered on ebay are the exact same dimensions. However, if you are looking for a larger radiator to keep your beast cool, this one definitely does the job. I would say go OEM but I am a sucker for aftermarket parts and OEM might not always be available.

I hope I can help a fellow member with this write-up and I apologize for any errors I may have missed. Let me know what you think.

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Thermostats only begin to open at their rating. They are fully open at 15 to 20 degrees above this. So a 180F thermostat is fully open (if ever needed) at 195F. So I guess engines under heavy load can safely run 15-20 hotter than the thermostat rating.


A sensor near the upper rad (where the hottest water is) will turn on the fan without even giving the rad a chance to cool the water first. Upper rad hose water will almost always be at or likely above the temperature of thermostat you are running (180 for the 710) The sensor should definitely be set for higher than the thermostat or it will run all the time.




My temp sensor (from a KA 240sx) is in the stock location in the 710 rad return line. Stock air con rad. The 240sx has a clutch fan but this is an auxiliary fan for the air conditioning if it begins to over heat in traffic. I believe it turns on at or near 198F. I can hear the fans come on at 2/3 the way up that 'run range' on the temp gauge. Car normally runs at about 1/2 the scale. They are also wired 'on' at all times and the fans can come on even after I exit the car. This is not a problem as they run less than a minute and prevents boil over during heat soak. 



Didn't notice if you have a coolant recovery rad cap and bottle, but they totally prevent constant topping up of the rad. 

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They are also wired 'on' at all times and the fans can come on even after I exit the car. This is not a problem as they run less than a minute and prevents boil over during heat soak. 


I've been doing this for years, and works really well here in Texas, and the 100+ summer temps.


Nice write-up Kathos.

But plan on having a spare fan set aside in 12 months, if yours was made anywhere in Asia.

I've been getting about 1 to 1.5 years out of them.

FlexLite & Spal last about 2-3 years, but cost a lot more.

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I have two Subaru fans but because of the rad width I can't fit side by side, I ran one behind and wired the other backwards as a push fan and mounted it ahead and to the other side of the rad. There is maybe 4" of overlap, shrug. I figure fans from cars that ran them are better than after market.

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That's a good point Mike. It probably comes on before it gives the radiator a chance to do its job. From experience I can tell you that my fans don't come on while I'm actually cruising around. Usually the fans kick on a little under the 1/2 level on the temperature gauge.


From the installation instructions: https://static.summitracing.com/global/images/instructions/der-16738_.pdf

" For best results we recommend installing the probe as close as possible to the water inlet of the radiator."


When you think about it, the radiator is getting airflow while cruising( fan on or not).. So the temperature of the radiator as a whole stays "cool". Because the probe isn't actually in the coolant, its contact is through the radiator fins, so I am sure that the heat of the radiator core also helps moderate when the fans switch on. If the thermostat doesn't fully open, it will take some time for the probe to read the increased temperature of the engine coolant. If the probe is all the way down towards the outlet of the radiator, your fans could be kicking on much later then when the engine actually reaches temperature.


I tried wiring the fan so it would stay on after I shut the car off for simplicity but I found that my fan ran for much longer than just a minute. Probably because the radiator is so large and also possibly because the probe is so close to the inlet of the radiator. I started worrying about running the battery dead so I modified it to run only when the car was on. So far it hasn't posed a problem but I am sure it works either way.

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I have no problem saying that. They make shit, their quality control is for sale and they are corrupt as fuck. Ya gets wat ya pays for. If it can leave you stranded or dead on the highway don't buy it from China. Lawn furniture.... maybe. People should be made to put a sticker on their cars if they install Chinese brakes, steering or suspension parts so I can get out of their way.

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