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1989 300SE
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6 Posts
Discussion Starter · #1 ·
Hi everybody...I am a newbie here to the site. I have been quite the lurker for a while, this is a great site that has been put together!!! I live in Orlando, FL, student at UCF, and bought a 1989 300SE last year from a good friend of my mom's. I am very handy with cars (I have a 95 camaro z28 back home running 12's in the 1/4, did all the work myself). I bought my 300SE for $900, since it wasnt running when I bought it. Just needed a new fuel pump and she was good to go. SO here is my new dilemma...

Ever since I have had the car, it likes to run hot when the car has been standing in traffic for a while. I assumed it was either the water pump, fan, or radiator. I never did anything, because the car would hold temp fine as long as it wasnt standing for long periods of time. About 6 months ago I replaced the water pump and radiator (since the water pump sprung a leak). The car is still overheating when I am standing in traffic. I noticed that the fan spins at a constant speed (it never speeds up or slows down no matter how hot the car is). I am assuming the fan clutch is the problem.

Is there anyway to tell for sure? If it is the clutch, how difficult is it to replace? Any input would be greatly appreciated. Thanks in advance!!! Pleasure to be part of the site...
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,449 Posts
Could be some kind of fan related thing. Make sure the electric aux fan is working.

The M103 engine runs hot. Mine gets hot sitting in traffic, and it gets very hot under the hood when the car sits after shutting it off. I actually installed relay and sensor to turn the fan on when the car has been shut off if the temp is over 100*C. It shuts off at 95*. On hot days it'll cycle 3 or 4 times.
 

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1989 300SE
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6 Posts
Discussion Starter · #3 ·
Could be some kind of fan related thing. Make sure the electric aux fan is working.

The M103 engine runs hot. Mine gets hot sitting in traffic, and it gets very hot under the hood when the car sits after shutting it off. I actually installed relay and sensor to turn the fan on when the car has been shut off if the temp is over 100*C. It shuts off at 95*. On hot days it'll cycle 3 or 4 times.
Appreciate the quick reply. I have checked and double checked to make sure the electric fan works. It does come on, but only when the A/C is on (which would make sense since it sits right on top of the condenser).

I, too, have noticed that the car gets extremely hot after you shut it off (creeping up to 100C sometimes). Usually when I am driving the car will hover right around 80-85C, but when I sit in traffic it will creep up to 110-115C if I am standing long enough. As soon as I start moving again, it drops within half a minute. Like I mentioned earlier, I have noticed that the mechanical fan spins very slow, no matter how fast the motor is spinning or how hot the car is. It is also very hard to turn when the car is off....
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,449 Posts
All of that is pretty much normal.

As stated, I added a device to turn my fan on at 100 celsius. It helps. Works with the car on and off.

Make sure you have fresh coolant and a good thermostat. If your radiator is gunked up with crap it'll run too hot as well.

You could replace the fan clutch.
 

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1985 500 SEC EURO AMG/LORINSER; 1988 560SEL, 1995 S500 Sonderschutz
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3,680 Posts
Try turning the fan with the engine off. There should be a little resistance, but not much.
 

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1989 300SE
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6 Posts
Discussion Starter · #6 · (Edited)
Try turning the fan with the engine off. There should be a little resistance, but not much.
I did that...there seems to be quite a bit of resistance on the fan. With a good push it will maybe spin about 1/2 a turn. As I stated earlier, I have noticed that the fan spins the same speed all the time when the car is running. Doesnt matter if the car is cold, boiling hot, at 3,000 rpm, or at redline.

How does that fan clutch work? I am assuming there is a bearing with some kind of bi-metal that expands as the heat comes off of the radiator...
 

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1985 500 SEC EURO AMG/LORINSER; 1988 560SEL, 1995 S500 Sonderschutz
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I did that...there seems to be quite a bit of resistance on the fan. With a good push it will maybe spin about 1/2 a turn. As I stated earlier, I have noticed that the fan spins the same speed all the time when the car is running. Doesnt matter if the car is cold, boiling hot, at 3,000 rpm, or at redline.

How does that fan clutch work? I am assuming there is a bearing with some kind of bi-metal that expands as the heat comes off of the radiator...
I wonder if you're referring to the right thing. There is the fan clutch which is belt driven and rotates according to engine RPM, then there is the auxillary fan which is on the front of the car that blows onto the AC condenser.

someone correct me if i'm wrong.
 

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1989 300SE
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Discussion Starter · #8 ·
I wonder if you're referring to the right thing. There is the fan clutch which is belt driven and rotates according to engine RPM, then there is the auxillary fan which is on the front of the car that blows onto the AC condenser.

someone correct me if i'm wrong.
The auxillary fan works perfect...it kicks on when the A/C is on. I am referring to the fan that is driven by the belt in front of the motor behind the radiator...
 

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1991 300SE
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65 Posts
the aux fan should kick on at a certain temp even if the a/c is not on. having your temp creep around 100c is normal in traffic. just make sure it doesn't go above 105. otherwise you might have some problems. also, if youre in slow moving traffic, turn the a/c off. it'll slow down how hot your car gets. I'm from LA so i know how this can be..
 

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2007 S550
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243 Posts
Blue,

I have a 1990 300se and have had the exact same problems as you. I have found that high temps while sitting is normal for these cars. I have replaced radiator, fluidss, hoses, thermostat, checked both fans, AC system, and everythng else. The car still drifts toward the high side while sitting. Once you move, its OK. An indy even replaced my Viscous fan because he did not think it was operating like it should. The car still ran hot. He eventually put the old fan back in. One thing he did do was change a relay or switch that was connected to the AC system and add freon. From what understand, the AC system not fully charged and operating properly will contribute to this problem. The A/C system and the cooling system some how work together. Now, although it still rises, it recovers very fast. Maybe this is a sign of other problems. I am having other work done later this month that may have contributed to the problem and will post results when the temps are warmer here.
 

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1991 300SE
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65 Posts
above poster knows the symptoms well. i drive a 300te, all the 3.0 I6 engines seem to run hot when stuck in traffic. it might help to turn on the EC button after the vents have gotten cold, then switch back and forth appropriately if you must have a/c on at all times.
 

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1990 300SE and 1995 C220
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2 Posts
Not sure if this is applicable to the US, but where I live, we inject silicone oil into the visco fan, creating more resistance, and therefore turning the fan faster. My 300SE used to run up to 105 as well in standstill traffic. Now only goes to 93 to 95. Also, you can add a thermoswitch that kicks in Hi fan mode when it reaches a certain temp. (usually 100C)
 
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