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1996 S600 Coupe
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191 Posts
Discussion Starter #21
So far I have only removed the expansion tank and drained the coolant. Someone's been there before me. The rubber grommet was missing. I noticed an unplugged connector hidden under the expansion tank, it looks like it leads to the air pump. Is that it?
The overflow tube is dried up and cracked .. it dissappears down through the wheel well.. I'm thinking of trimming it and trying to use it. I got all 6 o-rings for the thermostat housing , will remove water pump next.
 

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1996 S600 Coupe
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191 Posts
Discussion Starter #22
Here is the connector that was unplugged and the cracked tube circled in red.

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W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
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7,607 Posts
That is the Air Pump connector .
On mine it was also disconnected ,when i re-attached it ,for the 1st 60 seconds or so on cold start only ,you will hear a weird noise ,it will stop after a min . The reason on mine it was disconnected was ,Everything was completely blocked of ,all egr hoses-pipes to throttle actuator etc & cracks in the hoses . Replaced everything she is driving 100% .
 

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1996 S600 Coupe
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191 Posts
Discussion Starter #24
Nice, I have already bypassed my air pump with a shorter belt. I didn't know that it was never connected since I got the car.
I might plug it in if I get a good deal on a new/refurbished air pump.
I hope I didn't make a bad call changing the water pump .. the impeller doesn't slip on the shaft so that was not the problem.. but it does look old and rusty , possibly it had a small leak since it was wet in the area around the waterpump and caked on dirt.
I almost rounded some hexbolts for the thermostat pipes , otherwise not bad job.

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1996 S600 Coupe
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191 Posts
Discussion Starter #25
Does anyone know the part number for the 4 screws that goes through the thermostat pipes ?? 2 on each side . I want to order new ones. (Part 7 and 8 on the diagram)

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1994 S600 Coupe, 1995 S600 Coupe
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2,009 Posts
N914021008002 is the part number.
One thing I should have mentioned earlier is that I install all of the Allen head bolts with antiseize, both in that location, and the ones holding the thermostat, to keep from rounding out the heads in the future.

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1996 S600 Coupe
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191 Posts
Discussion Starter #27
Thanks a lot, unfortunately the dealer said that they were out of stock so I have to carefully re-use the old screws.. I will put a drop of oil on the threads , is there a specific torque spec ? I can't find any on these screws.
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,009 Posts
The long ones thru the thermostat housing are 9 Nm. The elbows into the heads are 21 Nm. Water pump to block at 21Nm. Pulleys on pump are 10Nm. Front mount bracket bolts are 21Nm.

Jon
 

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1996 S600 Coupe
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191 Posts
Discussion Starter #29
Wow thanks again , I'll be sure to torque to spec. So far I've only cleaned the gasket surface , had to stop early due to bad weather. In the opening above the water pump there's a ton of dirt but I can't really reach in there . That's work for another day..

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1996 S600 Coupe
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191 Posts
Discussion Starter #30
Finally some progress! I looked at the SL forum how someone did the water pump on same engine , he had to change water pump 2 times because the thermostat housing didn't align parallel with the water pump. Now it was my turn I work myself up starting with the water pump , then the thermostat housing, it had a big gap on one side and it was tightened all the way .. I had to loosen the water pump bolts to give it some movement , that was all that was needed to mate the surfaces straight. The trick is to torque the water pump bolts last!

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1994 S600 Coupe, 1995 S600 Coupe
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Thanks for writing that up. Haven't run into that issue, but may come in handy another time.

Jon
 
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