Eliminating the fan coupling-any issues?

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jjs2800cs

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Our 1970 2800CS water pump just died, so out is the radiator and off the old pump. With everything off I realized that years ago (at least 15 or so) I or the previous owner must have eliminated the friction fan coupling and bolted the red 5 blade fan directly to the water pump.

Living in southwest Florida we really have not seen any overheating problems. We do use the R12 AC in the summer occasionally and the aux fan comes on with the compressor. Also we have a way to manually turn on the electric aux fan even if the AC is off, but really do not have the need to do so.

Car is originally a 4 speed converted to a five speed. The radiator is from an automatic CS as I believe they are a little bigger and help in cooling. True?

So the question is, what is the down side to having the fan bolted directly to the water pump? Noise?, Reduction in cooling?, additional wear on the water pump bearing?

Any comments? Anyone else done this and if so what is your experience?

Also as a discussion can someone explain why cars use either a friction or the later viscous couplings? What is the advantage? Older cars all used to have the fan directly bolted to the water pump.

Thanks in advance

jjs2800cs
 
The old style friction clutch is notorious for failing and causing overheating problems. In the shop manual it says in case of failure to use longer bolts to lock it in place which is what I did with mine as I did not want to take a chance on this crappy design and blow the head up.

Having since upgraded to the viscous clutch/9 blade fan it is a world of difference, better cooling and efficiency with less noise. The fan only saps energy when needed vs 24/7 when it's bolted.

On a side note, I have triple webers and could not figure out why my front carb would flood at low rpm, it took me months of frustrating trouble shooting before I found the solution - the 5 blade fan creates a weird turbulence that caused the flooding. Possibly because the blades are assymetrical or because it was bolted to the water pump. No such issue with the 9 blade-nice and smooth.

I am not sure the cooling area on an auto radiator is bigger because there is an area dedicated to the transmission cooling. More important for hot climates like ours is having it triple cored.
 
Blades on the five-blade CS fan, and the 2002 fan, are not evenly spaced to avoid a resonance which could occur with evenly spaced blades.

Fan clutches all seem to look the same (I just replace one on the wife's Benz). Why couldn't they all be interchangeable? Because Hans is jealous of Fritz and neither likes Otto?
 
When I first revived my coupe I replaced the friction clutch and 5-blade fan with a viscous clutch and 9-blade fan. The only concern is that the fan is very close to, but has never hit the radiator. I could put the fan adapter in a lathe and cut about 5mm off the mounting surface to gain additional clearance. That had been on my to-do list for about 30 years.
 
Stevehose said:
... the viscous clutch/9 blade fan it is a world of difference, better cooling and efficiency with less noise. The fan only saps energy when needed vs 24/7 when it's bolted.
Click to expand...

To ask a stupid question: "how does the viscous coupling know when the radiator needs more airflow?".

Is it that the viscosity of a liquid inside the coupling lowers as temperature rises, and that makes the coupling lock up and start spinning the fan? And how does the coupling sense temperature - is it exposed to the coolant inside the waterpump? I'm not getting how this gizmo works.
 
Thanks for the info so far-but back to my initial question.

Anyone have their 5 blade fan bolted directly to the water pump and driving that way? We have no coupling, viscous or friction installed at all, so our fan is spinning all the time. Are we wasting energy (HP), not cooling as we should, or does it not make a great bit of difference?

Here are a couple of photos as installed.


Thanks

jjs64bj8
 

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I am not sure either but I believe as the temp heats up the resistance in the clutch increases and grabs onto the fan more than when cold.

jmackro said:
To ask a stupid question: "how does the viscous coupling know when the radiator needs more airflow?".

Is it that the viscosity of a liquid inside the coupling lowers as temperature rises, and that makes the coupling lock up and start spinning the fan? And how does the coupling sense temperature - is it exposed to the coolant inside the waterpump? I'm not getting how this gizmo works.
Click to expand...
 
You're probably wasting a little energy, but getting the max cooling possible out of the fan, and maybe more wind noise but not a big deal.


jjs2800cs said:
Thanks for the info so far-but back to my initial question.

Anyone have their 5 blade fan bolted directly to the water pump and driving that way? We have no coupling, viscous or friction installed at all, so our fan is spinning all the time. Are we wasting energy (HP), not cooling as we should, or does it not make a great bit of difference?

Here are a couple of photos as installed.


Thanks

jjs64bj8
Click to expand...
 
I have and always been (more than 10 years). The main symptom is the sound of revving higher. May be wasting energy and read about additional stress on the water pump. So far no issues. I do not think there is any harm in cooling too much the radiator coolant, in the end the thermostat determines when to let coolant in.

One day I may try the upgrade, which is what I have in the E24.


jjs2800cs said:
Thanks for the info so far-but back to my initial question.

Anyone have their 5 blade fan bolted directly to the water pump and driving that way? We have no coupling, viscous or friction installed at all, so our fan is spinning all the time. Are we wasting energy (HP), not cooling as we should, or does it not make a great bit of difference?

Here are a couple of photos as installed.


Thanks

jjs64bj8
Click to expand...
 
Since the fan is always spinning, could be that by having the fan bolted directly to the water pump may be part of the reason what I have not had any overheating problems here in Florida during the summer. The extra load probably true, but since it is so flat here (the highest point around here are speed bumps), and our drag racing days are over, maybe not an issue.

I am raising these questions because since I have it all apart, should I consider locating and installing the upgraded viscous coupling? But I am not sure it is worth the $$ in my case. So unless there is a real technically degrading issue, I will bolt the fan up the way it came off.

Any other comments?

THANKS

jjs2800cs
 
I don't think it makes any difference having it bolted to pump. If you go with viscous clutch you also need the mounting nose, reducing clearance. The latest pump uses a spin on bolt.

I would replace your upper hose with a proper BMW hose though!
 
The zip-ties on the upper left of the second pic made me wonder: do you have the rubber bumper on the radiator support bracket? It holds the rad in place for and aft, without having to zip-tie it to the front bulkhead.
 
To answer some questions being raised,

Yes the radiator hose will be replaced with BMW, one was not available when last had to replace them.

Yes the thermostat housing will be using a proper gasket, believe leftover from PO.

The tie wraps are just to keep the electrical wires in place which are for the AC compressor which was added a few years ago. The rubber radiator mounts are in place.

Thanks

jjs2800cs
 
As you can tell, we like to see everything nice and neat on our member cars :-) I'm prepared for tons of abuse when I get to Monterrey- mostly for deviating from stock :-)
 
When I bought my 2800 CS in 1980, it had the fan bolted directly to the water pump with longer bolts. I have continued to run it that way with no problems. It does whir a little at high rpm but that is not of great concern to me.

I was having a slight overheating problem around 2009. It was due to too many tubes being pinched off in the radiator due to leaks. I elected for a new core and the overheating problem went away.
 
The auto radiator is physically larger due to the tranny fluid reservoir on the right that cools the tranny fluid, but the coolant fluid volume and cooling surface area are no different.
 
fan coupling

Running fine without a fan coupling. I have a '72 CSA, so rad with trans cooling. Been 25 years without a fan or coupling. There is an electric control over the fan in front of the radiator, works well when temp reaches mid way of gauge, cools things down and have never had any problems. Asterisk....reside on the left coast of Canada, rare to have extreme heat...though this past summer I did identify "heat soak", and made adjustments to keep interior tolerable. Plus, low humidity. So...there's that. Mike
 
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