So, most people seem to be looking for a larger radiator to get rid of all the heat from built engines...searches would lead me to believe, anyhow.

But think I need a smaller radiator. Maybe the smallest one I can get.

I've swapped a 5.9 12 valve into my 79 Bronco and the thing just does NOT like to get to anything over around 170 and typically it'll stay around 150 on my gauge. It'll raise a little with boost, as I have a charge cooler that runs through the coolant, but it'll cool right back down. This is even in the summer with temperatures over 100.

I've verified the thermostat working with some warm water.

It'd be nice to have a heater that does more than just get the vents lukewarm.

I've considered blocking portions of the radiator but decided against it as I'd like to have some air flow over the condenser.

It seems like the best option is to run the smallest radiator that came stock in these trucks. What I have in there now is a new unit that I ordered for a stock 79 Custom with 400.

Would the radiator from a truck with a 300 be a little smaller? I'd LIKE to have something that fits properly in the stock radiator support, so for now I havent looked into swapping in something from a Dodge diesel.

 

The smallest radiator listed for the 78-79 Bronco was the standard cooling radiator for 351 w/ manual trans. The core dimensions are 18 35/64" High X 25 53/64" Wide X 1 17/64" Thick
The 78-79 F series is the 6 cyl std cooling 18 59/64" X 18 29/64" X 1 17/64". However, if you go back to the '73, it shows the smallest is for a 240 6 cyl., manual trans. 2WD w/ std cooling 17 3/8" X 20 1/4" X 1 1/4". But if you use this one, I believe it takes a different core support.

 

I really doubt it's a too big radiator. What temp is your thermostat? Have you verified the gauge reading? Fan clutch engaged all the time?

 

I have a stock thermostat of 180. There is no fan. Well, there is the electric one, but it never comes on. ever. I can look up what setting it is at when I get home and checkthe part number on the switch. The only way I've verified the thermostat is by installing a different brand in the same spot. The borrowed Autometer and my personal Equus read the same. Also, the heater is very cool at the core. Warmish, but not nice and toasty.

 

Depending on how you drive, tire size, gearing etc.....i doubt a 5.9 is even getting a workout in a Bronco. What RPM does the engine typically run at? Assuming your Bronco is fairly stock, other than its engine, im guessing that axle gearing for a 79 Bronco and a 90's Dodge are reasonably close, probably 3.54 or 3.73......Id start off by trying measure or research what the cooling system capacities were between the donor vehicle and your bronco........And yeah, its ironic with 90%+ of us trying to get increased cooling, you are the exception!

 

The 5.9 Cummins is notorious for being cold-blooded when not being worked hard...

Cardboard over the radiator is almost mandatory (in winter), if you're concerned about restricted airflow cut a 8-10" hole in the center.

I've heard the design of the oem Cummins T-stat maintains operating temps better than the cheaper aftermarket T-stats (I can't vouch for this personally).

Running a block heater helps too, instead of ambient air temp your coolant is already 100-120 degrees before you even start the truck.

 

The gearing is 4.11 and the tire size is 35". It puts things almost back to where stock was, as far as overall gearing is concerned; at least according to a comparison to my GPS vs. the speedo.

Anyhow; I've considered the cardboard item. I was going to 1-up it with some aluminum sheet and Dzus fasteners for easy install and removal...but the condenser, in front of the radiator, makes that a little less than optimal.

It may be the best option, though. It's hard to consider right now, cause I've been drinking a little...

The fan switch that I've been running is a unit from a Mustang, PN ECH FS125, on at 205 degrees.

 

Try the aluminum and cut a few louvers in front of the condenser. When it's ice cold I'm sure it doesn't need a whole lot of airflow.

 

I'll probably wind up trying the sheet, as it's free. But I'd LIKE to be able to run the heat and AC all in one day as weather here often dictates. It'd be nice to have stock like functioning out of this vehicle.

After reading parts of your thread I'm surprised you'd suggest anything like that.

 

Yeah I'd stick with the desert cool in my truck. But I know it's too darn big already. I know a stock dodge one will fit. If you don't mind spending the money definitely try the smaller radiator. But I'd have to say since yours is done and running I'd give that aluminum a shot before I tore down a functioning truck.

 

Wait wait...I remember talking to you about this at some point, but maybe I didnt get the whole idea of it.

Will a Dodge unit fit and just slide in? Same mounting points and all?? Cause...if it will, that's the answer right there, no problem.

I bet it's thinner than what I have too...

 

Actually, that would be pretty trick!

Better than cardboard which gets all soggy and wet.

 

I can vouch for using the cummins thermostat over other brands. Get one and you will be able to forget about this smaller radiator stuff, cardboard blocking radiators, shutters . All of it..

 

I have a Cummins thermostat.

 

No the cummins radiator mounts on two rubber mounted aluminum pins on the bottom and two aluminum forks on the top that are rubber mounted as well. The radiator is thinner though. It's around 2" thinner than my desert cool. Not a direct bolt in but should be real easy to make it fit.