Check out Steve Brotherton's comments in the following thread about testing a fan clutch.

checking 603 viscous fan drive

I think there's more to it than just seeing it spin freely once the engines warm. I changed mine out for this reason and saw no reduction in temp.

You mentioned early on about cleaning the radiator...bugs, etc. In my opinion, the only way to do this is pull the radiator and flush both sides once out. This will also allow you to do the same to the A/C condensor and in order to really do it, you'll want to pull the aux fans off so you have a clear shot at the whole front surface of the A/C condensor. While the radiator is out, you way wish to have a shop clean it professionally - inside and out.

If you're seeing higher temps on the highway, you could indeed have a blocked air path.

If it's running hotter only at slower speeds, it could be the fan clutch or a blocked air path, or ?????????.

Thanks Mike, good thread.

I had previously removed the rad and washed both sides, I also blew it clean and dry with compressed air - it was quite dirty. I didn't do the AC condensor. Upon inspection yesterday, my mechanic pointed out how dirty the condensor was.

I'll remove the rad again and clean the condensor fully - including removing the aux fans. If that doesn't fix the problem, I'll install the new (used) clutch. If that doesn't work it's time for a new rad and a new lottery ticket...

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

most stories like this turn out to be plugged radiators. you replace the thermostat, flush the radiator, worry about the VFClutch, replace the pressure cap and nothing works. i think that specially in the case of a used car where the PO didn't regularly replace coolant or used non-MB stuff, the deposits will accumulate and eventually clog some tubes. there have been recent cases when two year old radiators were found to be clogged and causing the elevated temperatures. i suspect that mine is not 100% free flowing anymore and have since moved to a "cooler" thermostat which is working for me. i don't believe that the citric acid flushes are enough to dissolve the types of clogging i am referring to. the rads have to be dipped in those special baths and the tubes reamed out. that, or get a new one -i would check out those remanufactured ones that are half the price....

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joE
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
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