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1997 S500 Coupe
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136 Posts
Discussion Starter #1
My dad bought superb 95 S500 sedan charcoal gray sort of color benz.

The car seems brand new in every way but it has two major problems, it wants to overheat and the AC doesn't work. Its engine temperature goes up to 110 C sometimes if it's in stop and go traffic during a hot day, our other two W140's never do that in our weather conditions in southern california.

So far here's what's been replaced with no luck:
- Radiator
- The one big fan in front of the car. (Auxillary Fan?)
- Thermostat (twice, to make sure it wasn't faulty, and am using one of them on my other W140 and it works fine)
- Water Pump (I think)

One thing we think is that maybe because the AC doesn't work, it doesn't turn on the two little fans infront of the one big fan (the ones that turn on when AC compression is high or when the car is overheating in emergencies). and maybe the AC somehow directs some of the cold to the engine? What other possibilities could there be.

The AC doesn't work due to a leak behind the front panel from the inside.. :'( Scared to take it apart to fix it, don't want any loose ends and the panel to make sounds. Right now it's solid like day 1 that it came out since it was never pulled apart.
 

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1997 S500 Coupe
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136 Posts
Discussion Starter #3
Ahh yes the fan clutch was the name I forgot.

Yes the radiator gets hot and is brand new, and the fan clutch works and is brand new too. They're the official parts and not used nor aftermarket.
 

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1997 S500 Coupe
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136 Posts
Discussion Starter #6
I appreciate your responses! I will look into buying those parts and trying it out. The AC isn't working, since there ir no freon so the two small fans don't spin in the front, so that may also be the issue.

We were quoted 1,500 - 2,000 for the dash disassembly to fix the AC leak, so I want to rule out the other cheap parts first :\ Will forsure change these parts in my Coupe too, just to make sure it runs cooler, since that car has no issues except running hotter than usual when I first bought the car (my coupe runs at 95-97 C when it used to run 83 C max, but this thread is about the Sedan that runs 100-110, just not to get confused) :)
 

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94 s420 250kmiles
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827 Posts
the electric fans are controlled by the A/C control panal if you have a blow fuse for any of the a/c system the fans will not operate
 

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Premium Member
1997 S600 (sold)
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4,660 Posts
Slowhands comment may be a little misleading, so just to be sure, the auxiliary fans (the electric ones) do not require the AC to be on in order to run. They should turn on by themselves at particular temperature setpoints. First at slower speed, then at higher speeds at higher temps. Certainly at 110 degree C coolant temp, I would expect them to come on.

Have you independently verified the coolant temp? Ping the metal coolant pipes with an IR thermometer.

Check fuses as mentioned. Check that the fans run if you put 12 V directly to them at their connectors.

Brett
 

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1996 s320
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16 Posts
Did you ever find a solution. My ac has a freon leak and my aux fans dont come on. My car overheats sometimes. Aux fans work if forced on or if ct sensor is unplugged.
 

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Premium Member
'97 CL600
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2,941 Posts
One way to check the operation of the two aux fans in front of the radiator is to turn on engine and put a newspaper over the grille. Watch the temp on the inside and you should hear the fans coming on. At least in my cars you can hear them. Note temp. Should be around 100-105C. My two 119 engines run below 90C even in the summertime here. (105-118F) The resistors that JimF sells will turn them on sooner. One day last summer it hit 118F. My car sat idling for about 10 minutes. It still blew cold air and barely moved on the temp gauge.
Anziani
 

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99 s320,and 83 300sd
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2,072 Posts
quit driving or you'll blow a head gasket.Check that air is out of system.I always drill two
small hole in thermostat so it will bleed air faster
 

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1996 s320
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16 Posts
i dont really drive the car. im going to change my thermostat today to see if it helps. My main concern is trying to figure out why my aux fans aren't coming on when engine gets up to 120C, Im thinking my temp sensor might be bad. because it can go from way in the red to normal operating temp in a couple seconds. As always thanks for any and all input.
 

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1985 500 SEC EURO AMG/LORINSER; 1988 560SEL, 1995 S500 Sonderschutz
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3,679 Posts
i dont really drive the car. im going to change my thermostat today to see if it helps. My main concern is trying to figure out why my aux fans aren't coming on when engine gets up to 120C, Im thinking my temp sensor might be bad. because it can go from way in the red to normal operating temp in a couple seconds. As always thanks for any and all input.
Wow, what is your coolant level at?
 

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94 S420 RIP 2/8/13 02 ML55AMG, 06 CLS55AMG, 89 Mas. 228, 84 Por. 911 Carrera, 93 Toyota t.t. Supra
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1,582 Posts
Would suggest you ping the thermostat housing with ir thermometer. It may be that the car isn't really overheating just running normally and the defect is in the water temp sensor. It's on the front top of the engine next to the fuel injection sensor. Mine started going bad and for a long time displaying a hot or overheated state. After I changed it I carried and used the ir thermometer to make sure it wasn't " acting silly" anymore.
 

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1996 s320
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16 Posts
Would suggest you ping the thermostat housing with ir thermometer. It may be that the car isn't really overheating just running normally and the defect is in the water temp sensor. It's on the front top of the engine next to the fuel injection sensor. Mine started going bad and for a long time displaying a hot or overheated state. After I changed it I carried and used the ir thermometer to make sure it wasn't " acting silly" anymore.
I am going to try to work on it this weekend. Is the sensor you are refering to one of the ones on the thermostat housing area or am i looking in the wrong area? Thanks for any input.
 

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2014 Mercedes S550 AMG Appearance Package
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756 Posts
Check ur radiator. Mine was basically full of corrosion on the cooling fins. When I removed it sounded like and looked like it was sand coming off of it. The fins were clogged from corrosion. New one and never moves off 82 degrees C.
 

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1996 s320
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16 Posts
finally tracked the problem down to my instrument panel. A light thump above the gauge will cause my temp hand to start reading correctly when it does act like the car is running hot.
 
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