External Oil Cooler Mount / Air Directional Flow Theory

[plywoodkid]

All,

I know there is a lot of threads regarding External Oil Cooler mounting and wiring, but I think I have a valid concern and just need to talk this through.

Particulars:

1970 Bus, Full-Flow, Ex. Oil Filter mounted under Driver’s Side Battery Tray, External Oil Cooler w/ Fan mounted on Driver’s Side of bus about a foot ahead of jacking point near middle of bus. Cooler is on top and fan is pointing towards ground. Fan is currently wired through a relay and is “pulling” air down per the factory setting.

My dilemma is that first I don’t think this mount is optimal, but I certainly don’t want to rip it apart. I should have mounted it with the fan pointing towards the floor of the bus.

Anyway, Derale recommends with the way it’s installed to continue to allow the fan to pull the hot air away from the cooler. However, the model allows the reversing of the blade and polarity to cause the fan to blow directly on the cooler.

Derale sent this response per how I have it mounted:

“There does not need to be airflow blowing along the top as the fan is creating its own airflow. The fan is going to have more suction therefore more airflow if its pulling by creating a vacuum against the bottom of the vehicle which means more heat coming out. All of our remote coolers are primarily designed to be pullers due to the higher efficiency and better airflow characteristics.”

I just don’t think air circulation under the bus is enough based on where it’s mounted. I’m no thermodynamics guy, but I feel I would get more bang for the buck by reversing air flow on to the cooler. But, this could simply be me not getting it.

Now, I do know and understand that “sucking” air away from the cooler lowers temps, but in my mind I would think it would be minimal.

Any opinions would be appreciated as I am really attempting to understand and get a better cooling situation.

[bsairhead]

Pulling air away from the body "heat sink" is optimal but at speed I don't now how efficient it would be. If you want to reverse fan direction make sure the fan blade is not an airfoil.

[SGKent]

you have to make sure that the fan cannot pull or push air around the oil cooler or that is where most of the air will go.
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[richparker]

My .02:

That’s fan/cooler set up is very exposed to the elements. Usually these fans are not water proof, more like water resistant. A drive through one good rain storm and that fan could be killed. Not to mention it’s exposed to road debris, anything could get kicked up by the front tire and destroy that thing. Also, I’m always weary of pulling hot air through the fan. I’m sure your fan blades are plastic, like many others are and I’d be worried about possibly melting the blades.

That set up wouldn’t last a summer of camping under my bus. I’m always crossing streams on dirt roads in the National Forest.
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’71 Westy build
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[plywoodkid]

Great points….

And Rich, you are correct. If I was using my bus like you were, I wouldn’t have mounted there either. Lots of Beach Day gatherings, cruises and V-Dub Events. I don’t think I’ve ever drove it in the rain…..even when I daily drove for it for two years. But that’s Ventura, California.

With that said, it is seriously exposed.

[bsairhead]

Looking at your fan makes me think it's designed to push air. Pusher propeller am I wrong?

[lonewolfone]

Those fans don't last, they don't like dust or moisture, I had 2 fail before I switched to a setrab cooler and fan.
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[plywoodkid]

[bsairhead]

[Cap10323]

[richparker]

I have a louvered piece of sheet metal protecting my cooler as well.
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’71 Westy build
Adventure thread
’65 Deluxe Build

[aeromech]

So you actually have two coolers plus the fan, right? It is possible to have too much cooling. You want your oil temp to be 185-220 or so. If it runs cold you accumulate water in your oil. Going down the road there should be plenty of airflow over your #2 cooler. Now, if you plan to do stop and go in Los Angeles in the hot summer you might need the fan.
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[plywoodkid]

Aeromech, you are correct Sir. Doghouse Cooler and External with Fan.

[RalphWiggam]

Are you sure you even need a fan?

[sodbuster]

I have run that same set up for about 17 years with one difference. the cooler sits between the frame rails instead of outside them. It will tuck up a little more too. cooling and airflow has never been a problem. My sink drain and rear sway bar hang lower than the cooler I also run an inline oil thermostat as well.

Best you trust the folks that actually made your cooler. You seem to have good info there. I'm betting they put more thought into it than anyone. in other words. Try not to over think it too much.

[vwwestyman]

I recall when I was looking at fans for my Bus' radiator, that most are more efficient when pulling/sucking than when pushing/blowing. It seems like the average was somewhere around 20% difference, but that was some time back so I could be making that up in my head.

Unless it is just a crappy model, the fan's blades are designed to have hot air passing over them-so that shouldn't be a concern.

Concerns about debris and the like are valid, though!
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[germansupplyscott]

We've been working on a complete oil cooler kit - to offer for sale - for a while. Two kits actually, one for Type 1 engine and one for Type 4 engine Buses. We use a Setrab fanpack and components - Setrab has a new line of billet filter mounts and sandwich plates with integrated thermostat, super nice stuff. The fan is a puller. The fanpack is very small but perfect capacity for the Bus engines. This kit has been installed in prototype form in 2 Buses and it works super well. Type 4 engines especially tend to run pretty hot oil temps and this setup keeps the oil at or below 185 all day long. There is a thermostatic switch for the fan and a simple shroud to direct air into the cooler. I think the ducting could be improved frankly, but it works.

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SL

[plywoodkid]

Thanks for all the comments. Very helpful. This will definitely assist me as I adjust in the future whether that is remounting and ultimately probably purchasing a new cooler set-up.

Based on the discussion and advice, I’ll leave the configuration as “pulling” and give it some run time and watch the temps. My sender is close to where the oil leaves the case. I also have a 3.5 sump as well. I have about 200 miles on this new engine. Like Aeromech and others have stated, I may need the cooler less than I think. While breaking the engine in, I was purposely was in a lot of stop and go situations, so maybe I misjudged some of the temps.

Scott, I really liked that prototype.

[mikedjames]

When I fitted an external cooler, I decided that for a horizontal radiator the airflow should go up as that would be the natural passive flow. Then I fitted a forward facing scoop made out of thin stainless steel sheet.. if it gets caught or crushed it gives way.
This way no big cooling fan at all and one less thing to break.

Drops oil temps about 20F. Still use the doghouse cooler.
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[plywoodkid]