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Old 03-30-2003, 08:28 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
Posts: 2,011
I'll assume that your 103 engine is configured the same as my '88 190E 2.6.

The engine driven fan viscous clutch does not fully engage until about 100 C, so in heavy stop and go traffic or idling in warm weather the temp will often creep up to about 100. You can tell the fan clutch is fully engaged by revving the engine to about 3000. If it's fully engaged you should hear a distinct roar, and you can feel greatly increased air flow.

The electric fans have two speeds and are partially controlled by the A/C system, so if you have the A/C on, the fan(s) will operate intermittently based on the condenser cooling requirement. The engine will often operate cooler in stop and go traffic if the A/C is on.

With or without the A/C engaged, the fan(s) will activate at their highest speed at about 110C and they can be clearly heard.

You can check the fan functions by allowing the engine to idle on a warm to hot day while observing/listening for the fans as the coolant temperature rises, and you can do this test with the A/C both on and off to gain a full understanding of the fan control algorithms.

From your description, I wouldn't conclude that you have a problem, but verifying fan operation can give you some peace of mind.

As time passes deposits slowly build up in the radiator, which will reduce radiator efficiency and cause the fans to work harder, and eventually the radiator may become so inefficient from deposit buildup that overheating is inevitable. The best way to insure maximum life from the radiator is to change the coolant every two years using an organic inhibitor based antifreeze such as MB antifreeze or (GM) Dexcool. Conventional inorganic inhibitor antifreezes with silicates, phosphates and other salts will clog up aluminum radiators a lot faster than organic inhibitor based antifreezes.


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