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Quote:
Originally Posted by gsxr
1) The OM603 FSM has data on how the original clutch should engage... usually when coolant temp is above approx 90-95C. HOWEVER, the replacement clutch (with plastic fan) is from an OM606 and the FSM is silent on engagement temp. I believe it is a higher temp, in search of better MPG and emissions. On my cars, it may not lock up until the dash gauge is in the 100-105C range (or maybe higher).

2) Remember that the clutch is triggered by the temp of the AIR FLOW directly on the face of the clutch. If that area of the radiator (or condenser) has airflow blocked, or if the radiator has a 'cool spot' right there, even a perfect fan clutch WILL NEVER ENGAGE. Many a clutch has been replaced when the real problem was either a bad radiator (not uncommon on the 603 for some reason) or dirty rad/condenser fins.

3) From what is described, I'd bet a 3.5L con rod ( ) that the new clutches are working perfectly, but that it is never 'seeing' hot enough air to engage the clutch. When it's locked and you shut off the motor, the fan stops immediately or within approx 1 revolution, at least both my cars did this when locked. I usually needed the ambient temps to be 95-100F and the dash gauge to be at 100-105C to get it to lock.

4) The vertical storage thing is, IMO, a crock of stuff. New ones are shipped in any direction. I believe this only applies to used clutches.

5) Anyone who thinks the fan doesn't do squat at freeway speeds should remove the fan in the summer and go for a drive at 55-75mph and report back. You may be surprised at the results. (Tip: Bring the fan with you, and the special tools, so you can re-install it on the side of the road.)

6) If the fins are all clean and airflow is normal, I'll almost guarantee the radiator is the problem. An IR thermometer is helpful here, or you can try to feel (carefully!) if the area in front of the fan is blazing hot like it should be with the engine at 100°C+.



Thanks for that input GSXR. Yesterday, I removed the radiator, a replacement radiator from about 4 years ago, and blew 100 psi compressed air through the cooling fins of the radiator and while there was no oily gunked on crap restricting air flow, I did see a small amount of sand blow out. Also, I blew air through the AC condenser, also not much came out.

As mentioned, I can hold the aluminum fan still at temperatures at or around 110c according to my dash gauge. I dare not go any higher!

So as far as I can see, this fan clutch does little to nothing since the aux fan will come on at 105c, and it does, and when it does it returns the temp back down to around 85c to 90c. So now I'm wondering, is the fan clutch for the purpose of kicking in only if the aux fan cannot retain, or contain extreme temps. In other words, an auxiliary for the auxiliary, (isn't that an oxymoron?)a back-up for the auxiliary electric fan?
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I am not experiencing overheat problems here, but rather implementing avoidance. My cooling system is (with exception of question regarding the fan clutch) the cooling system is 100% with new water pump, thermostat, hoses, aux fan, aux fan thermo sensor, and a recent new radiator, 4 yrs ago.

The OM603 diesel engine with original #14 head, is highly susceptible to cracking due to high heat, such as produced from faulty cooling system components. You need only overheat a 603 with #14 head once and it is toast!

I'm just trying to understand the if I have gotten 2 defective clutch fans, or is there nothing wrong with them. The possibility of blockage in the radiator, directly in front of the clutch fan seems unlikely in my case, so I'm looking for answers? ..................BB