I have a w124 my wife has a w124 and my step daughter has a w124. So basically I have 3 cars to keep up with. we all live in the hottest part of the state. There has got to be a better way to keep these cars cool. New radiators, Mercedes fan clutch, but most of the cooling seems to be from the electric fans which doesn’t make sense. Basically the fans intended to be used as an auxiliary are now ruining 90 percent of the time. It doesn’t overheat but the electric fans are running full blast to keep the temps under 110

One idea I had was to just ditch the clutch fan and put a nice big electric in there with a variable ramp up speed. Clearly the clutch fan isn’t doing the job

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

i did this and it helped...

https://www.youtube.com/watch?v=Jo0HZ7KbNSA

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Ya that would work but I’m trying to take the Work load away from the Aux fans. The main fan should do most of the work. If there ever was a problem with the electric fans the car would surely cook

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

Iirc the electrics are there for the a/c system more so than the engine cooling. As long as engine stays at 110 and ac blows cold I'd run it.

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Jim

does the main cooling fan roar at all?

in february, I helped a person here with a W124 E320 and got him a good fan clutch and installed it. That thing definitely roars now when driving in 99F weather and the AC cranked up, the engine temperature is pretty stable at the usual 100C mark.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

It pulls air but I can’t say it roars. It’s a bran new behr. All 3 cars have the same Setup.

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

If its the same quality as the BEHR found on the 95 E300, then its a poor excuse of a fan clutch, I actually refilled the fan clutch of my old E300D with a thicker oil and got great results, uptil the time I changed it for a sachs branded one.

The fan was extremely loud when locked on, I think the original fluid in the clutch is too thin and causes too much slip and leaks too easy.

The guy whose W124 E320 I helped with had a sachs/horton clutch installed by me on his car and it was perfect - I had to use compressed air to clean the condenser fins and also washed it off of some non-corrosive condenser coil cleaner to remove road grease from it. This work definitely improved airflow a great deal lot.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Have you had the cooling system pressure tested?


These are old cars. Water pumps have probably deteriorated on all three cars.
I've had the same problem on W124's I've owned and then made the misfortune to install a cheap PRC water pump. Replacing a water pump on the M103 is a job you only want top do once.


After two less than effective pumps I bit the bullet and installed an OEM Graf. Never had an issue after. Even 40+ degree (110F) days, the auxiliary fan hardly came in.

And I'll put my habd up as well and recommend the Sachs fan. Beware there are a lot of cheap fan knockoffs with the Behr name on them.

even the original slim type behr clutch is useless, to make it work you need to fill it with 12000 cst oil, otherwise it doesnt engage.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Your best bet is to buy a brand new BEHR fan clutch. Been there done that.

You can also put in an electric fan with an adjustable probe switch that slots into your radiator. Of course switch the fan with a relay.

The reason why a radiator probe is better than a cylinder head sensor is because your engine/transmission will run cooler (with a cylinder head switch your cut in temp has to be higher that the thermostat temp. otherwise the fan will run all the time)

Running your car at 110 will damage your head gasket (already a weak point on M104), wear out your transmission sooner, wear out your rubber/plastic parts on the engine and cause leaks.

The electric fan(s) should be on pretty much any time the A/C is running. Ambient temps over 85 degrees should absolutely have the fan on if the A/C charge is correct and the compressor is running. This will be low speed, not high speed and is designed to help the A/C work better, not to cool the radiator.

The fan clutch is thermostatic. If air is not reaching the thermostatic element, it will not engage. Make sure that the radiator and A/C condenser are clean, they can plug up with debris and block the airflow to the thermostatic element. If the engine is running hot and the cooling system is working as it should be, that fan should be engaged and moving a large amount of air. If you open the hood and rev the engine, you should hear it whining and see/feel a substantial increase in airflow from the fan.

New doesn't always mean good. Behr clutches can be hit or miss. Verify that it's working properly before dismissing it as a possibility.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Just installed a new Nissens radiator, Behr fan clutch, thermostat and did a flush. Temperature stays rock solid just a pinch above 80. M103 1990 300SE.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

Everything on the cars is fresh. I been replacing the fan clutches On all 3 cars every other year or so. A lot of money going down the drain. I feel the main fan should be doing more work than what it is currently putting down. I’m going to swap in an electric fan on my w124 and see how much better it works. It’s hot where I live. 100-115 degrees Typically the whole summer till Late September. It’s calming to have a car that is functioning within a normal area instead of 2 **** hairs from boiling over

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

Don't know if this helps, but our fan clutches for Mercedes lean toward the "aggressive" side of the spectrum (we've received some complaints that they make the fan blade too loud). But if you're looking for maximum cooling, an aggressive clutch might help.

Our engineers are currently looking into tuning them less aggressively in the future, but we haven't made any running changes on the production line just yet.

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URO Parts online catalog: https://apaindustries.com/catalog

snj:

Prior to settling on air flow as the culprit, ensure that the thermostat is operating correctly. If it is not fully opening, it is also not fully closing the by-pass circuit. If the by-pass circuit remains partially open, the recirculated hot water will defeat radiator and air flow capacity.