87 124 cooling fan upgrade SERIOUS issue
 

OK, I've had several 603 powered 124's at this point. the original cooling fan is a 9 blade aluminum fan on a large viscous clutch. the clutch is EXTREMELY expensive, so many have found the Turbo 606 clutch to be a less expensive upgrade. however, it will not work on the aluminum fan, either the mass or something else will cause the clutch to fail prematurely. so getting a new Turbo 606 fan blade along with the fan clutch is a great alternative.

DO NOT USE THE 9 BLADE PLASTIC FAN ON THE 124 with a 603!!!!

many have noticed the notches on the back tips of the original aluminum blade. this was to allow clearance to the intake boot that passes through the heat shield. this is a consideration when choosing a blade, but it's not a deadly sin if it's not matched, as the na 606 blade has a smaller diameter, and a much rounded profile compared to the stock blade.

HOWEVER! the 9 blade FLAT EDGE blade will cause SERIOUS DAMAGE TO THE RADIATOR!!! it's mounting face is much further back on the hub of the blade, which makes the blade faces closer to the radiator.
this sounds like a good thing, since the blade being closer to the radiator should draw more air through it... the problem is that on the 124, the fan clears the cooling surface of the radiator by about 1" on the passenger's side... so being closer to the radiator means the blade can contact the flange of the radiator.
it's happened to TWO of my radiators... took me a while to figure out what was happening, as sitting still the motor is still a good and solid point, and the blade is at least 1/2" away from the flange...
BUT! when the clutch fully engages, the blades FLEX TOWARDS THE RADIATOR... the tip hits the edge, and POP the radiator tube ruptures, and coolant is lost.

I'll post up some pics, as I just got home from fixing the mess with an 11 blade Turbo 606 fan... I'm tired.

I think the flat edge fan is from a 602... not a 606, and it WILL NOT BE SAFE ON THE CAR!!!

Ouch
 

The pictures will be interesting.

.

John I had a problem with a 124 eating radiators under panic stopping. I took the car to a frame shop owned by a friend. The lower radiator support is at parking block height and easy to knock in by previous, less vigilant owners. They pulled my lower radiator support by 3/4" and I haven't blown a radiator in two years with a plastic fan.

I looked over the lower rad support, and while it's been bumped a few times, the radiator is the same distance from the fan top and bottom, so I don't think that's it.

+1. I had the same problem on multiple cars. You can't really measure from fan to radiator to check this, you need to measure the distance between the mounting holes for engine splash shield.

Also: The 9-blade plastic fan is specified in the EPC as the correct replacement for the 124.133/.193 (1987 300D/TD) when the clutch is replaced. There is nothing wrong with this fan if you have the correct part number and have it installed correctly. The original clutch + metal fan was replaced by new clutch 606-200-00-22 and 9-blade plastic fan 606-200-00-23. The lack of notches in the blades is irrelevant. I had this setup on my '87 for years with zero issues. I later changed to the 606 turbo clutch with 11-blade plastic fan (pics here and here).

What part number(s) did you have installed?

:detective:


9-blade plastic fan 606-200-00-23:
http://img.eautopartscatalog.com/hir...0388129MEY.JPG

http://www.w124performance.com/image...clutches01.jpg

I'll post part numbers and pictures asap.

keep in mind, the motor mounts on the car I'm working on could be sagging. that would add complexity to the equation...

That is another likely cause. Weak motor mounts can let the engine move forward under braking, especially hard braking. Normally there should still be enough clearance, but if combined with the lower radiator support pushed in maybe 1/2" (or worse), the result is usually a sliced radiator tube.

:nuke:

I have an OM603 part no. BEHR clutch with MB star with 04 roundel stamp on my OM606.910 along with the rounded blade slim fan. According to your description my setup should bring the fan real close to the radiator.

I removed old grayish fluid and refilled it with Lucas 3000 cst fluid (fill and tested 3 times) and it couples and decouples correctly, But I believe this clutch was made to turn either a heavier fan or a fan with wider blades as I feel the drive is really strong for that poor looking fan. Ive been told by a mechanic that some early OM606 used this clutch.

I have not tested an OM606 clutch, I have only seen another car with it and it was quite slippy - meaning that it only lazily tried to follow engine rpm - hence very quiet too, This one roars to action. My engine temp never goes more than 95 though with A/C in TX summer.

btw you say that the fan bends forwards, I have seen mine bend a bit backwards when I raise engine rpm when the fan is working.

Yeah I was wondering about that, it would seem that the air flow would bend the blade tips in the direction of flow.

You've got centrifugal force acting radially about the hub and force from the air flow axially in the direction of flow, I.e. towards the engine. I can't think of any forces going toward the radiator in the fan. I'm not a mechanical engineer somebody correct me if I'm wrong.

I can't see how the blade can bend forwards. Unless it is due to the action of the clutch and it causes the fan hub to somehow move forward when the clutch engages at temperature.

my thinking is the blades grab more air, pulling the blades towards the air source... not blowing them with the flow of the air...

don't think of it as centripetal force, think of it as FLUID DYNAMICS and the fluid is air, and the faster the blade spins, the greater volume of air being forced through the blades, and the plastic stretches with the load.

I'd change the motor mounts before we get into fluid dynamics.

Actually vstech is correct. The fan blades are in essence small wings which are moved through the air mass by the engine. The angle of attack creates a low pressure area on the "top" of the wing (the surface facing toward the front of the vehicle) and a high pressure area on the "bottom" of the wing (the surface facing toward the engine). This pressure differential does two things - first it "pushes" the air toward the engine (also "pulling" air in through the radiator) and because of Newton, the action of the air foil puts a force on the airfoil bending it toward the front. Most fans and propellers are very stiff and we can seldom actually see the flex, but occasionally we can view it, as in the photo of this helicopter lifting a very heavy load.

http://www.peachparts.com/shopforum/...1&d=1349407444

Under load and with increasing speed, the forces will bend the blades of our cooling fans toward the radiator, potentially enough to cause damage if the clearance is less than designed.

Centripetal force will tend to cause the blades to straighten out counteracting the lifting force. Again we can see this in helicopter blades at rest. The blades droop until the centripetal force straightens them out and then they can flex upward under load.

http://www.peachparts.com/shopforum/...1&d=1349407784

considering the above excellent explanation - why am I seeing the blades bend backwards when I rev the engine with clutch engaged. Is it due to the blades having a rounded profile on the tips of the blades?

what you are seeing is more than likely an optical illusion from the spinning blade profile flickering in and out of your visual markers...