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Discussion Starter #1
Since purchasing my 500SEL I've been trying to chase down why it seems to run warm. I've been through every post I can find about overheating and running hot and have came to the conclusion that I needed a radiator and fan clutch. Each was done at different times and had an effect on the running temps. Unfortunately I feel it still runs too warm.

The old radiator was definately clogged as once the car was hot it never cooled off. The fan clutch was also on its way out as even at 100C I could easily stop the fan with a rolled up newspaper. Since changing them the temps stay around 82-90C while driving with an ambient temp of about 18.3C. Which is much better than before when it stayed between 95-105 and depending on driving conditions and ambient temp it frequented 110C+.

My question is how hot should the car be at idle and how should the temperature act when coming to a stop? Most recently after changing parts it idles around 97C and coming to a stop after a highway run it will get to 105 but then settle back to 97C until I begin driving again at which point the temp comes back to the 82-90 range.

The thermostat is new but I don't know what temp it is. I'm running the brand new blend of MB coolant (the blue stuff) in a 60/40 mix. I might try a bottle of coolant enhancer like water wetter or purple ice.

Are my temps normal? Could there still be a problem? I've read about everything from running lean because a clogged fuel filter to clogged cats to incorrect tire pressure.

Any help would be greatly appreciated and I'm sorry to start another temperature thread. :surrender:
 

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sounds about right my cars operating temp is between 80-96c.
but i did a little computer trickery to have the electric fans come on around 90C
 

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Discussion Starter #3
sounds about right my cars operating temp is between 80-96c.
but i did a little computer trickery to have the electric fans come on around 90C
It runs in that range all the time? I'm concerned that its going to run way too hot with higher ambient temps.

I'm trying to not worry about it since Mercedes designed it with the electric fans not coming on under over 100C.

Changing the resistance of the temp sensor doesn't have any effect on cooling when the AC is on correct? I should have mentioned that these temps are with the AC on and the electric fans never came on.
 

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It runs in that range all the time? I'm concerned that its going to run way too hot with higher ambient temps.

I'm trying to not worry about it since Mercedes designed it with the electric fans not coming on under over 100C.

Changing the resistance of the temp sensor doesn't have any effect on cooling when the AC is on correct? I should have mentioned that these temps are with the AC on and the electric fans never came on.
the fan always comes on when the car reaches 105c factory setting, and around 90c with the resister mod no matter what.
i also added a swich to turn the fans on high when i need it.
 

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Discussion Starter #6 (Edited)
I added a resistor to the connector as shown on K6JRF's website and the fans never shut off. This mod works on a 93 500SEL? When I remove the resistor everything operates as normal.

I used a 1.1K ohm res.

Oh and incase this tells you anything, the fail safe when disconnecting the plug completely doesn't work. Disconnecting the plug makes the fans shut off if they are on. I only tested that theory when disconnecting the 1.1K ohm resistor. Not from having everything connected normally (no resistor) then disconnecting the plug. So maybe it was confused? Unfortunately it got too dark to play around..
 

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make sure your fan relay is working there are 2 of them on our cars, the big one turns on the fans high, and the small one next to it slows it down, to the low setting.

also try 1.2k and 1.78k
 

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Discussion Starter #8
I knew I should have ordered the other resistors as well.

Is there an easy way to test the relays? I just assumed they were working properly since the fans come on at the correct temperature and speed up as needed. Though there is obviously a problem since they don't go into failsafe mode when the connector is removed from the sensor.
 

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Discussion Starter #10
They were running even when I turned the AC off.
 

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1997 S600 (sold)
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They were running even when I turned the AC off.
Earlier you had said you had the AC on and the fans were off. I don't think that is proper operation. I'm fairly certain the fans should turn on whenever the AC is on.

Later you said the resistor caused the fans to run all the time. I don't know what effect the resistor that you used should have. Someone else will have to address that. The K6JRF cool harness fix should work on your SEL.

Brett
 

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Discussion Starter #12
Sorry if my posts have been incoherent or confusing.

AC on, No Resistor, Sensor connected = Fans only run if temp gets to 100C
AC on, Resistor, Sensor connected = Fans on 100% of the time
AC on, - , Sensor disconnected = Fans off

AC off, No Resistor, Sensor connected = Fans only run if temp gets to 100C
AC off, Resistor, Sensor connected = Fans on 100% of the time
AC off, - , Sensor disconnected = Fans off

AC on or off, Resistor, Sensor disconnected = Fans run 100% of time.
 

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Discussion Starter #14
Correct, I understand that. But thats not whats happening in my case. I'm hoping someone might be able to point me in the right direction as to why its doing what its doing.

From what I understand the fans should turn on full speed if I disconnect the two wire temp sensor. correct? When I disconnect that sensor the fans do not run.

With the resistor in place the fans turn on as soon as I start the car. Independent of the temperature.

BUT! If everything is connected normally the fans work properly.
 

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I read all of the previous posts, but it sounds like the car is operating within the normal temperature range. I live in Wisconsin, and this summer has been brutal, the entire month of July was 90+, all month. I ran the AC constantly, and the car never saw temps over 100 degrees C, so it seems to be well within the acceptable range.
 
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