I got a problem from my W126 280se.My radioator overheating.If i no turn on the A/c the temperature is 80-90 in between,but if i turn on the A/c the temperature will go up 100-110.When i driving fast with A/c the temperature will decrease until 80-90,if i idle the temperature will increase until 100-110.I just changed thermostat,clean up the radioator and change new A/c fan.But still the same problem.Anybody help me please!!!

Thank's
Mercw126

sounds right to me. The a/c puts a lot of heat in front of the radiator. Since you did all this work make sure that all of the air is bled out of the system.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

what you mean is {all of the air is bled out of the system. }
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Yes, unfortunately, your experience is what the rest of us experience, too. If you have already done the obvious maintenance, like clean out between the A/C condensor and radiator, and checked to be sure that the auxilary fan(s) comes on correctly, de-scaling (cleaning out) the inside of the radiator and maybe adding a wetting solution is all that's left to try.

As a long-time MB owner and fan, it pains me when MB does things that seem so obviously inferior, and engine cooling is right at the top of the list, along with anemic A/C systems, but they are what they are.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

all my the radioator is clean up already,but still the same problem...Help!!!

As long as it is not in the red you are ok. I live in south texas and with the a/c on in traffic, the temps rise pretty good, but i have never had a problem. Well the only problem is that the a/c sucks when the car is idleing.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

finally i fit my mercedes w126,the problem is the temperature swift problem.Thank's for everybody

Aux fan come on w/AC ???????????

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A Dalton

Was suffering this same issue on my '01 SL600. Finally got it fixed, but it wasn't cheap...

-New Fan Clutch ($411) with 2mm shaved off the actuator pin to lower the engagement temp to around 85c.
-New Radiator ($480ish)
-New Water Pump ($300ish)
-De-scaled cooling system w/vinegar, then flushed w/ a cooling system flush product.
-Custom-built T-stat, with 71c vernatherm swapped into an OEM housing in place of the stock 87c one ($150ish), from PTE over on MBWorld.
-Modified electric fan harness with resistor to engage at lower temp (free, thanks to good ole' kjcrf).
-Bunch of A/C work done also, ($1500). First, the car had a slow leak so the system was usually low on freon. Then in addition, the expansion valve was stuck, and the compressor was getting weak. All of this in turn caused the electric fans not to engage properly, or to engage too slowly when they did engage, because the internal refrigerant pressure sensor never sensed the correct internal pressure to engage the fans as required by conditions, which in turn further helped increase the coolant/engine temps.

Car now runs 81c on a normal day, 85c on a real hot day with the a/c on max. Everyone told me my old temp fluctuations were 'normal', but the M120 is an aluminum block and I just wasn't comfortable running around with 110c+ coolant temps, I felt eventually I'd wind up with warped heads if I didn't do something.

As a side note, when the car was new, it was always pegged at 85c no matter what. I assume the same for the W124. But as they age, all of these components (radiator, water pump, t-stat, etc.) slowly lose capacity due to internal and exterior aluminum corrosion, scaling, and general wear & tear. Truth is, 110c-120c temps really aren't normal in an 80's/90's Benz, at least in the sense of how they came from the factory. They are only normal in the sense of "well, a lot of them now have this problem...".

Your issues are some probable combination of electric fans being tired or not engaging properly, weak fan clutch, internal cooling system scale, or internal and/or external corrosion on the radiator, a sticky T-stat, leaky/weak water pump, incorrect coolant mixture for your geographical climate, or A/C system issues. The other thing that amazed me is, the mixture in my car was originally almost 60/40, coolant to water. Here in Florida you can easily get away with 30/70. Changing the mixture so that it was appropriate for the climate where the vehicle operates, plus adding some water wetter, brought the temps down a good 5c-10c just by itself.