I don't know what else to try to make my 300e run cooler, I use waterwetter in the radiator, have flushed the radiator several times. during the hot part of the day the aux. fan almost runs constantly.
What are my options

How hot are we talking here? Mine runs 100 to 110 and I think it's in good shape. The only anwer may be Flagstaff.

Don't waste your money on Water Wetter.

In the summer in Phoenix with the A/C on you're not likely to see the coolant temperature drop below 100C in the heat of the day.

There nothing to worry about unless it starts pushing 120 C.

Duke

You live in an oven. The car is going to run hot. What color is it?

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Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

The aux. fan is going to be on if your a/c is on, especially in phoenix.

If you are sitting in traffic it's pretty hard to get the air to move across the radiator.

Try using Mercedes Benz coolant with distilled water. Is your water pump, thermostat, radiator, radiator cap in good shape?

Consider a new radiator, etc, or a custom one made, and possibly a new fan/fan clutch.

Take off your belly pans (the covers under the car) off, that will get some more air moving around, but consequently the engine compartment will get dirty.

How how was it today 108 degrees F outside, and you are running 110 degrees C on the water?

Hope this helps.

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Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

I also live in Phoenix and have a 1989 260e which has the m103 engine and the cooling system is identical. A week ago I installed a Behr thermostat rated with a 79 degree celsius rating rather than the factory 87 degree. I bought it from an independent MB facility in Scottsdale. I don't believe it is available from MB. My car is running noticably cooler although it will still reach 105 C if sitting idle for prolonged periods. The part number is 100-200-07-15 e-mail me if you have any further questions. Tom

A new radiator may be in order. After 15 years it is probably pretty clogged both internally, and inbetween the rows of fins on the outside. It might not be easy to tell how dirty it is without taking it out of the car.

Also, at the very least, you should remove the front fan shroud (the one that covers the electric fans) and clean it out. I was shocked at the amount of road dirt trapped inbetween the front shroud and radiator on my '90 300CE. It was like my radiator had on a fur coat. Temperatures are noticeably lower since I did this, but coolant temps rise fast on my car too if I'm in traffic with the a/c on.

GregS

Radiator/coolant system problems have plagued me more than any other, so I have learned a thing or two along the way.

I'll probably get some flak for suggesting this, but reduce the coolant mixture to, say, 5% (or less) coolant to 95%+ water. Nothing absorbs heat more effectively than water. Anything mixed with it simply reduces its heat absorbing capability.

I have been doing this for the past two years and, in 90+ degree summer weather, I run at 80 to 82 on the highway and about 90 in stop and go traffic. I don't generally go over 90 to 95 unless I am idling in traffic jams.

Also, make sure your cooling system is airtight. The tiniest leak will lower pressure and decrease cooling capacity.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

You can change the ratio between water and coolant some and it will help. However, I wouldn't get carried away with it because the coolant has the additives needed to lube the water pump and prevent corrosion.

I'd go 55/45 or 60/40 at the most.

I also live in the Valley and my '91 300E operates normally with temps no higher than 105. Generally it's under 100 if I'm moving. I'm running a 50/50 mix of MB coolant and distilled water.

IMHO, the thing that screws up cooling systems more than anything else is the use of tap water. I avoid it like the plague and never have problems with MB cooling systems. BMW's are another story

What is it about tap water that is bad? I would think distilled, which leaches minerals like a sponge, would be more corrosive.

Also, does anyone know what the specific lubricating/anti-corrsion additives in coolant are?

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2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Distilled water isn't corrosive when mixed with coolant. As for tap water, it depends on where you live. In Minnesota it was iron (among other things).