SL/R107: 107 owners - check your fan clutch
08-31-2010, 02:01 PM
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107 owners - check your fan clutch
Just a heads-up to fellow 107 owners. My 560SL was not overheating per se, but it was running really hot. Once the temp gauge climbed up over 100 degrees C, it never came down. Stop and go driving was death: the car would often stall even though the temp was not technically in the red zone. Reading in another forum, I found one possible cause of the excess heat could be a faulty fan clutch.
The fan clutch is a thermo-mechanical device, meaning that it functions in direct relation to the temp. Over time, the fluid that makes the fan tighten up when hot leaks out, evaporates, or whatever. The result is a fan that will spin freely at all temperatures – which means that it does not move enough air through the radiator or over the engine.
I could take my fan and spin it freely by hand when the engine was hot (and shut off!) so I knew that it was shot. It looked like a simple enough DIY: just four 10mm bolts on the water pump hub. With some models, you may have to remove the fan shroud, but I did not. It’s simple, but not easy: only a small 10mm box wrench will fit in between the bolts and the fan hub. It takes a while to get’em out. Leave the bottom-most bolt in – it will help with getting it aligned again. [Also, do not run the engine while the fan bolts are out: I did so to back the car out of the garage for better light, and the belt pulley rotated on the water pump hub such that the holes did not line up. It took a few clicks of the key to spin it back in place.]
I had ordered a replacement fan clutch through Performance Products. The price was right, since the OEM replacement was astronomical $$$. The fan blade assembly is attached to the clutch with four more 10mm bolts, so you remove these and transfer your fan blade assembly to the new clutch. Make sure you tighten the bolts well and use a cross-over pattern when tightening, like you would with one of the wheels.
So now my new fan clutch assembly was ready to go back in. After a painstaking ½ hour of threading the bolts back in and working them in a quarter-turn at a time with the 10mm box, it was on. Now the fun starts.
I gave the fan a turn just to see how it was and found that the blades now scraped against the belts. The fan blades were now too close to the motor, plain and simple. Performance Products had sent the wrong part. Check the photo below – the new part is on the left, the old on the right:
As you can see, there is a 5/16” difference in the bolt flanges. The new part put the fan blades just close enough to contact the belts. So out came the bogus part and I shipped it back for a refund. Cost me $13 in postage just because Performance Products could not get it right. Unfortunate - I used to like shopping there.
Hat in hand, I went to my local MB independent mechanic who agreed to get me the correct fan clutch at a reasonable price. Fit like it was supposed to!
The difference was amazing. It moves so much more air now that my rising temperature problem seems to be gone. I took several test drives with mixed highway and stop-n-go driving and the temp never went above normal. Maybe slightly above normal at stop lights, but nothing like before.
The one down side, if you can call it that, is the noise. The new, properly-working fan now has the car sounding like Grandma’s old Hoover vacuum cleaner at start-up and when the car is under throttle. Although it’s reassuring in a way, knowing that the car is now moving enough air, but the turbine-like noise must be dealt with. There is only one solution: moving ahead with my exhaust modification plan to drown out the fan noise!
So the next step is: Magnaflow cat, delete resonator, stainless steel pipes back to a new Magnaflow muffler to replace the rotting OEM stuff. I can’t wait.
The fan clutch is a thermo-mechanical device, meaning that it functions in direct relation to the temp. Over time, the fluid that makes the fan tighten up when hot leaks out, evaporates, or whatever. The result is a fan that will spin freely at all temperatures – which means that it does not move enough air through the radiator or over the engine.
I could take my fan and spin it freely by hand when the engine was hot (and shut off!) so I knew that it was shot. It looked like a simple enough DIY: just four 10mm bolts on the water pump hub. With some models, you may have to remove the fan shroud, but I did not. It’s simple, but not easy: only a small 10mm box wrench will fit in between the bolts and the fan hub. It takes a while to get’em out. Leave the bottom-most bolt in – it will help with getting it aligned again. [Also, do not run the engine while the fan bolts are out: I did so to back the car out of the garage for better light, and the belt pulley rotated on the water pump hub such that the holes did not line up. It took a few clicks of the key to spin it back in place.]
I had ordered a replacement fan clutch through Performance Products. The price was right, since the OEM replacement was astronomical $$$. The fan blade assembly is attached to the clutch with four more 10mm bolts, so you remove these and transfer your fan blade assembly to the new clutch. Make sure you tighten the bolts well and use a cross-over pattern when tightening, like you would with one of the wheels.
So now my new fan clutch assembly was ready to go back in. After a painstaking ½ hour of threading the bolts back in and working them in a quarter-turn at a time with the 10mm box, it was on. Now the fun starts.
I gave the fan a turn just to see how it was and found that the blades now scraped against the belts. The fan blades were now too close to the motor, plain and simple. Performance Products had sent the wrong part. Check the photo below – the new part is on the left, the old on the right:
As you can see, there is a 5/16” difference in the bolt flanges. The new part put the fan blades just close enough to contact the belts. So out came the bogus part and I shipped it back for a refund. Cost me $13 in postage just because Performance Products could not get it right. Unfortunate - I used to like shopping there.
Hat in hand, I went to my local MB independent mechanic who agreed to get me the correct fan clutch at a reasonable price. Fit like it was supposed to!
The difference was amazing. It moves so much more air now that my rising temperature problem seems to be gone. I took several test drives with mixed highway and stop-n-go driving and the temp never went above normal. Maybe slightly above normal at stop lights, but nothing like before.
The one down side, if you can call it that, is the noise. The new, properly-working fan now has the car sounding like Grandma’s old Hoover vacuum cleaner at start-up and when the car is under throttle. Although it’s reassuring in a way, knowing that the car is now moving enough air, but the turbine-like noise must be dealt with. There is only one solution: moving ahead with my exhaust modification plan to drown out the fan noise!
So the next step is: Magnaflow cat, delete resonator, stainless steel pipes back to a new Magnaflow muffler to replace the rotting OEM stuff. I can’t wait.
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Arik Yakir (10-21-2020)
08-31-2010, 10:16 PM
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