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radiator to fan clearance

fordfan

Contributor
Bronco Guru
Joined
Sep 13, 2009
Messages
3,503
Why are these Broncos so hard to cool? I know a lot has to do with certain mismatched parts, mods, etc. But my question is why doesn't other Ford vehicles with SBF motor have these problems. The 60's Mustangs have a smaller looking radiator, and the engine is just a tight under the hood as the Bronco. Maverick's, Granada's, Econolines, etc. I find it hard to believe that our Broncos with the larger Radiators than the vehicles I just mention have such a problem over heating when simply just driving in traffic. I have a new 4 core radiator, factory shroud, factory everything under the hood, and everything is brand new, I mean everything including the factory overflow bottle. I got so mad last week when I was in some traffic and it started to heat up, I drove it home parked it in the garage put the car cover on it and will probably not get it back out until fall.

Hey Clarrance,
I think the problem with your Bronco overheating is because it is so BLACK and so SHINEY! If it was grey primer, you probably wouldn't have a problem!;D;D
 

pbwcr

Sr. Member
Joined
Jul 11, 2007
Messages
623
After much research with the fan sellers my conclusion is 1" between the rad and fan and 1" between fan tip and shroud is correct. I would not go less that 1" tip to shroud because when you get all twisted up on the trail the thing will hit*. The 1" may be hard to achieve depending on the choice of engine and shroud.
In and out of the shroud is also dependent of fan choice. Not much I could do about that due to my engine choice. Consult with the fan maker. If that fails shoot for 1"
Agree to close to the rad is bad for water crossing as well and reducing the effective area of the air column. The shroud is supposed to deal with moving the air across the whole rad and to close affects the performance of the shroud.
My rig came with the shroud off center compared to the fan and with a terrible fit to the rad. Yup I ended up cutting it apart and reshaping the thing to fit and making it have the 1" tip clearance and a nice snug rad fit. I used epoxy, fiberglass with metal inserts for my fix.
* (The result is the shroud was broken and the water pump bolts were stretched and complete loss of coolant resulted. Bummer)
PaulW
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Why are these Broncos so hard to cool? I know a lot has to do with certain mismatched parts, mods, etc. But my question is why doesn't other Ford vehicles with SBF motor have these problems.

Shame to miss out on some fun because of a problem like this clarrance. But I can also understand the frustration.

I've been convinced for a long time that radiator size and capacity is not really the main, or certainly only underlying issue with Bronco cooling. At least where a stock or very mildly modified EB is concerned anyway.
Only because I'm pretty confident that the Ford designers did take the usual things into consideration when they originally put these rigs to paper.
Though from what I remember, I'm pretty sure that the Ford truck radiators appeared to me to be smaller than the comparable GM and Dodge truck radiators of the day.
And while I heard a LOT of complaints about running hot from Ford full-size truck owners from the early to late seventies, I never heard of any that from any of the other brand's owners that I knew. Pretty much ever.
So maybe there's something underlying all this whole "size matters" thing after all?

Not the cars so much, but the truck radiators always looked smaller. Could just be the footprint/shape though, as I've never compared fluid capacities before. Hmm, maybe that'd be an interesting thing to find out.

You can't really compare any truck to any car of this vintage either, I don't believe. Aerodynamics and weight and engine tune and gearing and tire size/rolling resistance alone, when new and then after modifications, can all play a huge role in how air flows over the fins and how many BTU's are generated by an engine for a given use. BTU's, Calories, Watts, whatever unit of measure they use for heat generation from an internal combustion engine an the cooling system's ability to transfer that to the air, are all I'm sure a bit different for the cars. The theories are the same, but the actual realities can be very different.
If nothing else, I think that "most" cars had more thought put into the aerodynamic flow stuff than "most" trucks did at the time. So they might just throw a bigger heavier radiator at a truck than a car, but that was not always enough.

The trucks are heavier, have traditionally lower powered engines of the same size (more torque at lower rpms usually, but still less overall HP) carrying that greater weight, use different gear ratio equivalents, have much poorer aerodynamic shapes to push through the air, and so have a HUGE difference in how efficiently air flows over, under and around the radiators.
The high-pressure areas under the front end alone are hugely different. Add a foot or two of height change to the equation, not only with lifting the truck, but with the larger tires and that high-pressure area increases it's effect massively.
And since those same larger tires are also harder to get rolling and keep rolling, the engines are working harder even without adding anything else to the mix. Keep the same gear ratios too then, and the load on the engine has increased by quite a bit. Enough perhaps, to overcome any oversizing of the cooling system that might have been built into it almost 50 years ago.

So while none of that may have any bearing on why yours runs hot, they're all things that can add up to overcome any extra capacity for heat dissipation that the factory had ever imagined they'd need, and had built in to the design of the truck.
Make one undercalculation then, in capacity or presumed ability to flow air over the fins instead of around them, and it won't take much to push it over the edge.

Change the engines too then, whether just in tuning or in especially in an overbore, which is acknowledged as a quick way to run hotter in a Windsor-family engine, and that's just one more nail in the coffin.

For comparison to what I just rambled on about, I don't remember ever hearing of a stock Bronco that ran hot around here back in the day. From the first one a friend of ours had in '66 at Lake Isabella, to the brand-new '77 that a neighbor brought home in San Jose, to all of my buddy's rigs. None of them ever had a complaint about it being even a tiny bit hot on the hottest days or worst commutes. The first time I remember a slightly hotter running Bronco, was a friend's '72 AFTER he'd rebuilt the engine and added a 4bbl carb and the infamous "RV" cam and headers.
Darn thing always ran slightly hotter after that. Before that it was perfect.

When they were mostly stock and the only changes were to cut the fenders and put on "massive" 32" tires, overheating just wasn't an issue around here. Nor was it with customers when I started working in the 4wd industry. No internet to compare notes back then of course, but between magazines and word of mouth, the word about heat was just not an issue.
I remember maybe a couple of people talking a bit about it in Southern CA, so it wasn't completely unheard of. But it was never much of a deal either.

We never ran over temperature when doing the Rubicon in the height of the summer, or daily-driving in the city, or on any trip anywhere.
But that was stock...

Paul
 

Jeff10

Contributor
Bronco Guru
Joined
Feb 20, 2011
Messages
2,137
Loc.
Indianapolis
Hey Guys,

I spoke with Bill Williamson at Ron Davis.

He was pretty convincing that the blades needs to be half out of the shroud. He wasn't aware of any data which specifically supported that way of thinking; but, he talked of some practical experience. If I remember correctly, he thought the restriction caused by the turbulence could be as much as a 50% reduction in air flow through the radiator.

As much as I would like to leave the shroud the way it is, I won't be able to rule out the importance of the 50/50 rule of thumb until I try it. I'll take a look at moving the radiator hose back; but, I'm not sure I can do anything about the power steering belt. I should probably just bite the bullet and cut the shroud.

Bill really was very helpful. I would definitely talk with him again about cooling issues. (We discussed fans and pumps, too.)

I guess I'll be doing some shroud work this weekend.

Jeff
 

ScanmanSteven

Bronco Guru
Joined
Dec 19, 2010
Messages
1,129
So I'll throw some confusion in here. I have a mildly built 351 EFI with headers and the Explorer front serpentine. I used the BCBroncos 4 core 3 pass radiator and built a fan shroud out of sheet metal with the fan totally enclosed in the shroud. Lots of air flow and no overheating problems, even when idling on trails in 90+ temperatures. Thing is, I'm not sure what in the combination works, but it does. My wife's Liberty has a totally enclosed fan so that's the pattern I used. Now, fuel pump, filter and the like is a different story. My point is I'm not convinced a full shroud is a problem, plus I've got a Warn 8274 winch.

So I just checked, the fan is about 1/4" recessed with less than a finger clearance between the shroud at the top and hasn't hit yet that I know of.
 

Jeff10

Contributor
Bronco Guru
Joined
Feb 20, 2011
Messages
2,137
Loc.
Indianapolis
Hey Guys,

Here in Moab today it was in the 90s. The Bronco (although I haven't compared the temperature with a known good gauge) was shown to be running between 190 and 200.

My main reason for the follow-up post concerns a response I received from Ron Davis (Bill Williamson). I had written again saying that I was concerned that cutting the shroud could make the problem no better, or possibly worse. With no guarantee, I hated to just cut the shroud. Bill asked if I had tried putting a business card against the radiator with the motor running. At 800 RPM the airflow through the business card against the radiator. His response to an email describing the results said that he thought I had good airflow.

We'll hit some trails tomorrow, so I'll report back with additional temperature readings. For now, I am thinking that there is good airflow across the radiator.

I'll keep you posted.

Thanks

Jeff
 

red hot71

Sr. Member
Joined
Nov 26, 2009
Messages
648
Loc.
kent wash.
If it has to be modified I'd rather be cutting than adding.

Before cutting I'd look at the coolant recovery system first, making sure its doing its job. That way even if some is pushed out, its recovered and drawn back in when cool. I feel a closed cooling system that doesn't allow any air into the system when its cooling will give you better cooling, over the long term.

I too believe 1" fan to radiator would be the best.
 

Jeff10

Contributor
Bronco Guru
Joined
Feb 20, 2011
Messages
2,137
Loc.
Indianapolis
Hi red hot71,

The coolant recovery system appears to be doing a good job. I am going to check the fluid level in the radiator later this morning; but, the overflow has been filling when hot and drawing down to the proper level when cooling. I'm pretty pleased with it.

It was only in the low 90s here in Moab yesterday, so it wasn't too hot. We ran some trails and did some moderate rock crawling. There were only two situations that caused the temperature gauge to read in the range of 230 F. One case was doing low speed crawling on ascents. The temperature would drop to 190 (on the gauge) when we leveled out and built a little speed. The other case was when we were on the highway... driving at 60+ at about 3,000 RPM. The highway driving also caused the temperature to increase to about 230 F.

Based upon the temperature at higher highway speeds (at least it's high for this Bronco), I am thinking it isn't so much an air flow issue across the radiator. (Who knows, maybe the winch motor is creating too much turbulence in front of the radiator at highway speed?)

For now, I think I will leave the fan and the shroud the way they are.

I'll write more if anything changes.

Thanks

Jeff
 
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