300E Runs Hot With New Fan Clutch - PeachParts Mercedes-Benz Forum

mike690003 · #1 03-15-2004, 07:14 PM

Hello Board,

I Just Got My Fan Clutch Installed Today And The Car Is Running Hotter Than Before, It Usually Ran At About 88C And Now Its Running At 100C, What Could Be The Culprit?????

#2 03-15-2004, 07:16 PM

Is this happening in stop and go traffic or going down the highway? If in stop and go, the culprit could be your aux fan. Check the fuse and spin the fan by hand to ensure that it is free.

Hope this helps,

Duke2.6 · #3 03-15-2004, 10:43 PM

Sounds normal! The fan clutch tightens based on radiator exit air temperature. This typically corresponds to a coolant outlet temp of about 100C.

It's been so long since my electric fans engaged, I can't remember if it's 105 or 110.

Duke

Ali Al-Chalabi · #4 03-16-2004, 04:28 PM

Remember that the spec for a brand new fan clutch is fully engaged by 96C-104C.

mike690003 · #5 03-16-2004, 05:41 PM

This problem happens when the car is stop and go traffic. The aux fan kicks in and reduces the temp to about 80C, but I just do not like the fact that the temp gets so high. I have a:

New water pump (6 months old)

New radiator (1 month old)

New coolant tank and cap (6 months old)

New aux fan (6 months old)

New fan clutch (2 days old)

New creamic aux fan resistor (1 day old)

Is there a resistor or fuse on the 300E that keeps the fan running on a low speed all the time?

I bought the ceramic resistor for the aux fan, but it made no improvements.

The car does not overheat, but at idle the temps rise too high for my liking, the cooling system is fairly new, and the car still runs hot! What could it be???

Duke2.6 · #6 03-16-2004, 09:39 PM

Quote:

Originally posted by mike690003
This problem happens when the car is stop and go traffic. The aux fan kicks in and reduces the temp to about 80C, but I just do not like the fact that the temp gets so high.

Normal!!! That's the way it's designed. The engine driven fan clutch tightens at about 100C, but the fan doesn't draw much air at idle speed. At 105 of 110 the aux. electric pusher fan(s) mounted in front of the radiator engage at high speed.

In stop and go traffic the engine coolnat temp may actually be, on average, lower if the A/C is on because the A/C pressure switch will engage low fan speed periodically.

Duke

Ali Al-Chalabi · #7 03-17-2004, 01:23 AM

I believe the temperature cut-in for that vehicle for the electric aux fan is 107C and cut-out above 100C. Air conditioniong will also make the aux fan come on depending on pressure.

Mercedes designed this car so that below 95C without the A/C on, there should not be any fans doing anything to provide mass airflow through the radiator. It is supposed to reach at least 95C in traffic. This is what the engineers wanted it to do.

Your fan clutch is operating as it should. You got a brand new part that is functioning as it should. If, with the old fan clutch, it never even reached 90C, I would assume the old one was broken and cutting in too early, as a new part should not bahave like that.

Rafi · #8 03-17-2004, 07:47 AM

most responders say that is how it should be. The part I do not understand is why is the temperature going up and down so much ~85 to ~100 driving vs idleing, why isn't the thermostat and all other components doing their job and maintaining a constant engine temperature. I also do see a yo yo effect after my water pump started leaking, before changing the water pump I do not think I saw that or I did not pay close attention. Before anyone says I need a new thermostat, This is my third theromstat after the water pump change.

toknow · #9 03-17-2004, 10:41 AM

I installed a new fan and clutch last summer (sachs) for my 300D '87 (124). It took me a good driving in a hot day to actually make the fan clutch starts locking and it did good job since then. It seems that these clutches are stored horizontally, which is wrong according to MB CD. The fan clutch works with a valve that opens using a pin, I think this pin can be stuck untill the clutch is USED hardly. My advice is to make SURE that the clutch is engaging, before anything else, it makes all the difference. you should hear the fan roaring at the start (cold) and when revive the engine at idle when it is hot after driving.

Duke2.6 · #10 03-17-2004, 11:53 AM

Quote:

Originally posted by Rafi
most responders say that is how it should be. The part I do not understand is why is the temperature going up and down so much ~85 to ~100 driving vs idleing, why isn't the thermostat and all other components doing their job and maintaining a constant engine temperature. I also do see a yo yo effect after my water pump started leaking, before changing the water pump I do not think I saw that or I did not pay close attention. Before anyone says I need a new thermostat, This is my third theromstat after the water pump change.

Where is the "requirement" to maintain constant temperature? It's not Mercedes or any other OE as most cooling systems are set up similarly.

The thermostat begins to open at 87 plus or minus a few degrees tolerance. In mild weather at freeway speed it should not run more than 90 on the gage, but you get into traffic with no air flow through the radiator and the temperature rises. At 100C the fan clutch tightens and increases air flow through the radiator. If the temp still rises to about 105 the electric fans engage at high speed and quickly cool the engine. As long as you are in stop and go driving without the A/C on this cycle will continue.

The C5 Corvette guys have the same complaint. The only fans are electric and without the A/C on they don't engage until 227F, but at freeway cruise the coolant temp usually runs 190-195F.

The job of the cooling system is to maintain the coolant temperature in an acceptable range, not a constant value, and the normal range for the wide range of driving conditions is about 85 - 105C.

Duke

Ali Al-Chalabi · #11 03-17-2004, 06:28 PM

The engine is not supposed to maintain a constant temp regardless of conditions. Everything is functioning as it should when the car warms up at a stop in a mechanical cooling system.

If you think differently, you may want to call up the engineers in Germany and explain to them why they are wrong and have they have made a mistake in building cars for the last 50 years.