Cooling off the Early Broncos
by Greg Banfield 
Early Bronco Editor

My Bronco has never ran cool in the summer months here in Phoenix, AZ.  We have blistering summers here that exceed 110° degrees on a regular basis.  This year I wanted to find a way to keep my Bronco cool.  The first thing I did was pose the question to very helpful Early Bronco Mailing List (EBML).  After listening to the numerous suggestions, the analysis began.
  • Does it  have a fan shroud?
  • Does it have the stock metal fan?
  • Does it have a flex fan?
  • How old is the flex fan?
  • How far into the shroud is the fan?
  • What size is your radiator?
  • Do you have good flow through your radiator?
  • Do you have a thermostat installed?
  • Do you have anything blocking airflow through the grill?
  • Is your timing advanced too far?
  • Is your motor running lean?
First thing I did was put a new thermostat in the truck.  It was suggested to me to install a 195° degree thermostat to keep the water in the radiator longer than if I had a 180°.  That did not work.

I went down to Checker's and bought a $20 can of  '40 BELOW®'.  Followed the instructions on the can and proceeded to go 4 wheeling on Upper Terminator and she still ran hot!  220° plus!

The next thing I did was pull my radiator and take it down to the radiator shop where they pulled it apart and told me I had no obstructions and it flow tested perfect.  He then mentioned to me that flex fans go bad.  After years of flexing the metal fatigues and starts to flatten out closer to an idle than it should.
I had heard of people using electric fans, so I measured the distance from my water pump pulley to the inside of the radiator and it was 2.5".

For an electric fan to replace the mechanical fan, it needs to cover 80% of the surface area of the radiator.  A stock Bronco 3 core is 19" x 19" = 361 in^2.  That means you would have to put on an 18" circular fan.  I searched exhaustively trying to find an 18" electric fan with that profile.  I thought "No Problem", I will just put a pusher fan in front of the radiator.  


So homeward bound I went to get all the correct measurements to see what will fit.  I first pulled off my winch, then removed the grill to expose the sub frame that the radiator is attached too.  What I found out is there is only a 10" x 19" window to the radiator from the front...... 
What were the Ford engineers thinking?  Very limited air flow to start with.  Now that I had an idea of what kind of space was available, I went and purchased a brand new 18" flex fan (Imperial Part# 221618) to replace the 8 year old one currently on the vehicle.
After careful measurement and looking at the shape of the 10", I realized I could fit two 10" electric pusher fans (Imperial Part# 226110) in the space up front.  They had a short profile that would fit between the sub frame and the grill.
While I had the front end apart, I decided to take my power steering cooler and transmission cooler and attach them to the radiator, since I would have the additional cooling of the electrics. They were a perfect fit in the 10" x 19" opening.  The are both the MaxCool brand from Checkers.
Next, was figuring out how to mount the electric fans.  Due to the hood latch assembly I could not attach both to the radiator as I had hoped.  Instead I welded little L brackets to the sub frame to hold the fans.


Once mounted, the wiring was routed across the top of the sub frame and under the lip to the passenger side wheel well where I mounted a Constant Duty Solenoid (Overgrown Relay) to handle the amperage of both fans.  They came with an installation kit.  All I used was the 10 gauge wire that came with it.  I had my own switch for the relay and used misc. connectors.  Both fans were wired for pusher style.

With the fans installed it was time to put the grill back on.  I took a picture so you can see the fit.


The next trip I went on with Arizona Classic Broncos to Peck Canyon was the test.  I was able to keep the Bronco at a more steady temperature than before.  It still ran about 195-205°.  If I forgot to turn the electrics on, it would get up around 220°.  Once they were turned on again, it would quickly go back down.  

I recently learned on the EBML about balanced thermostats.  I installed a balanced 180° this weekend.  A balanced thermostat is guaranteed to open within 2° of the set point to eliminated higher deltas with the cheaper thermostats. (Robert Shaw #330-180) Performance Unlimited


Two more things I did to assist the cooling efforts was to ventilate the rear of the hood above the fresh air vents.  The vent box on the driver's side was completely removed and capped to let the air go out the vent holes in the rear of the hood.  On the other side the box was ventilated to let air flow through and up and out the vent holes.  Also the hood scoop was opened in the front and the back for air flow.  I removed 1/2 to 2/3 of the wheel well on each side to let the heat from the mild steel headers escape.  The temperature is much more stable now and with the fans running you can really feel the heat coming out of all the vented areas.

If you need additional information on any of this process or wiring diagrams for the fans, just drop me a note at

Some useful links I found along the way!



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Property of Greg Banfield
And may not be reproduced without the 
Expressed written permission of 
Greg Banfield
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