A few weeks ago, I had to replace my water pump due to leaking at the weep hole. While there, I also replaced the thermostat. Both items were oem Mercedes. Since then my operating temps have increased by 8 to 10 degrees C. I used to run 85 when driving and 90 at idle. In extended stopped traffic it would creep up to 100 but not higher. Now the thermostat starts to open at 80 and will settle in 85 to 87. At idle it will go 95 to 100 and as soon as underway drop immediately to 87 to 90. This is all without air running. If I turn on the AC, at idle it will soot up to 105 and kick on my aux fans.

The viscous clutch seems to be functionally properly, aux. fans, etc. When I check the radiator it is hot at the top and gradually cools down toward the bottom hose. I appear to have good flow and you can tell when the upper hose gets hot and the bottom one warms up but is much cooler. This would seem normal and the radiator is working ok? What could be different since the water pump and thermostat replacement? Is the thermostat working properly or should I further investigate the radiator? System was flushed last year, and I replaced the coolant again when I replaced the pump with a 50/50 mix of MB coolant. What would indicate proper t-stat operation and radiator functions?

Any advice would be appreciated.

Thanks, BDBENZ

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87 560 SL
93 300E 2.8
91 300CE-24

Classic syptoms of a bad visco clutch.

Check it hot (when the gauge is near 104) by watching the fan while someone shuts the car off. Must stop almost instantly (less than one revolution). If it spins any more than that, it's toast. You should also hear it in traffic, it makes enough noise. Comes on when the air temp at the fan is 90C or so, so will show up at just higher than normal operating temp.

It will also roar for a couple of seconds when started cold -- certainly if you don't hear/see this, it's bad.

New clutch fixed the TE last year, same symptoms, including the water pump.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I will check the viscous clutch more closely tomorrow.

Thanks,

Bill

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87 560 SL
93 300E 2.8
91 300CE-24

Was the jiggler valve on the t-stat positioned at the highest point on the t-stat housing?

I've used both the Behr and Wahler t-stats in my 103 system. The Behr runs hotter even though both are rated 87C. Not saying this is how it always works - just what I've experienced.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Check the input and output temps on the cooling hoses routing to and from the water pump. If the input is as cool as I think you are saying, you may have a flow problem (like a stat not opening all the way). Might buy a summer stat to check it with, they're cheap (79C stat# is 110 200 06 15) and buy a IR thermometer -- they're indispensible

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Don't ask me, I'm a shop-owner by default