Temperature readings dont look bad with a/c on , but with a/c off it shouldnt go over 90. I would still put a thermostate in it regardless, when you do waterpump or radiator it is a good rule of thumb to replace thermostate. They are cheap and they do go bad at the wrong times.

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euro 287
Mercedes Technician 7 Years (retired to Hyundai)
2000 Dodge Durango
98 Mazda truck

I wonder if 90 degrees is even hot, though,

If you think about it, with an 87 degree thermostat, the temp that your t-stat starts to open is 87 degrees - not the temp that it is fully open, but the temp that it starts to open. I'm sure your car should be running between 87 and 92 degrees most of the time when running on the freeway, and will probably run about 100 degrees at an idle in hot weather. Here is what the CD says about the cooling system and temperatures on M104 engines:

Thermostat will start opening at 85 to 89
Thermostat will fully open at 102
Viscous fan clutch will cut-in at 96 to 104
Viscous fan safety cut-off will ocurr at engine rpm 4500
The same will ocurr at fan rpm 3250
Electronic fan (1st stage) will cut in at 16 bars of refrigerant pressure)
Electronic fan (1st stage) will cut out at 11 bars
Electronic fan (2nd stage) will cut-in at 107
Electronic fan (2nd stage) will cut-out at 100
A/C will go into 50%on, 50%off cycle (20 seconds interval) at coolant temp 121 to 123
A/C will go into emergency shut-off mode at 126 to 128
Pressure cap will open at bar 1.3 to 1.5
Coolant temp max is 130

Remember that water boils at 100 degrees celsius, but with a 50 / 50 mixture of water to coolant, your boiling point is raised to 120 degrees, and the car isn't considered to be overheating until the temp exceeds 130 degrees.

MB designed these cars to run hot, and 100 degrees is not even considered close to being hot. Your thermostat isn't even in the fully open position until 102 degrees. Further, the 2nd stage high speed fans comes on at about 107, and shuts off at 100! How can 100 be considered hot if that is the temp that the high speed fan shuts off at?

Now, many of us on this forum (including me) doubt the wisdom of the brilliant German engineers for these cars, and carry out modifications to prevent the car from going much over 100 degrees.

I have installed the "cool harness" that JimF sells, and it causes the high speed auxillary fan to engage at 100 degrees, and runs until the temp reaches 82 degrees.

I am convinced that your car is running at exactly the temp it is supposed to, but I'd still only run original MB coolant.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

All the Mercedes cars I have had show 90 to 100c when pulling a long grade (6 to 8 miles at 6 to 8 percent) even in winter.... Often with the AC on and out side temps from 100 to 118 F. I see it above 100c but never up into the red.. In general the thermostat does not really open until about 90.. So does run at about that on the long pulls in winter.. They do run at 80 or so down the road unless the out side temp is above 100 F then with the AC on even on the flats they run a little below the 100.. and a little below 80 on the 6 or 8 mile down hill grades in winter.. This is the way all the Mercedes I have had in the last 40 or so year have run.. 80 seems way to cool for a car that has an engine that is working hard.. I would worry about running that cool in the summer... I would for sure change the themorstat on one that ran that cool in summer..

Ken

True, and the design of the system to be under pressure raises the boiling point of the mixture significantly as well. (PV=nrT)

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1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick

Man, that's a cool formula. It makes me feel like I said something scientific, I just wish I knew what it stands for...

Pv=nrt

Hmmm...Paul likes Vanilla ice cream, but Never on Tuesdays

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

That is funny.

gee, my kid who's in high school was just asking me about that equation. can she email you guys about it? :p

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joE
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
http://banners.wunderground.com/bann...L/Key_West.gif

suginami,

Thanks for the info, it eases my mind a bit.

My school of thinking comes from old detroit iron in the 60's and 70's, and is hard to shake. It just seems like we are messing with mother nature.

I need to catch up with things and rembember that my 30 year old 4.5 has never overheated.......I just worry to much.

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Tim
300CE
280SE 4.5
Sandals (size 11)

My 93 300E M104 tends to run much hotter w/ AC on, the auxillary fans don't kick on until it reaches 110 or so. Aren't the Aux fans supposed to kickon when the AC compressor kicks on?

Please help,

Also, how are you supposed to properly flush and bleed the M104 engine.

Please advise.

Eddie