Hey guys,


I have no idea whats up, but on occasion I can hear a groaning from the engine compartment, and what sounds like a low whine when I'm on the highway.

My thermostat is wicked amounts of wacky; It'll peg itself at 120 and jump down to 60 on a whim.

I assume the first is my fan clutch? Is that a tough job to do for a light DIY-er?

Also I've read it's best to do the thermostat and a coolant change at the same time; what do you guys say?

the 560 has officially gotten to 213,000 miles today, still running strong (I'd prefer to keep it that way).


Thanks a lot,


Carlen

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1987 560SEL (210,000 miles)

There are plenty of threads here about testing and replacing the fan clutch assembly, so I'd start with a search.

I am getting an odd noise on occasion from mine, but I think in my case it is the power steering pump starting to get old.........

As to changing the coolant, I figure if you're gonna get glycol all over your hands anyway, you might as well change the coolant while you're at it.

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

The whine and the temp variations could be related; the thermo could be bad, and the clutch could be tightening and loosening randomly (maybe a result of the thermo going bonkers).

Although thermostats usually fail in the closed position, I have seen aftermarket thermostats flex and bend the pellet support, causing the thermostat to partially fail in the open position. The better ones (cost a couple $ more) have this area beefed up to eliminate the problem.
If yours is indeed stuck open, and the fan clutch locks/unlocks randomly, that could be the whine you hear and cause the wide swings in temp.

Contrary to some posts, what I have observed of a good fan clutch is that it will turn very free under normal engine temp conditions, under 100 degrees C. You can raise the hood on a just-driven car, and spin the fan 10 revolutions with one hard flip of your hand. If the AC is on and has the electric fans running, the clutch fan will spin freely like that.
When the motor is stone-cold, or quite hot (over 100C) without the AC electric fans on, the clutch tightens up and will spin only one turn or two by hand.
That's just a rough way to check general condition of the clutch.
I only hear my fan roar for a few seconds when I sit in traffic with the AC off (no electric fans on) and get things good and hot - water temp over 100 -then accelerate up to speed.

DG

I'll test it out tomorrow after my drive to work (45 mins on I-95, ugh).

I don't think it's my pump, as it groans when I'm in park or moving in a straight line; plus I had that replaced maybe 20,000 miles ago...

I don't know if it's just me, but my viscous fan is definitely spinning when in park after driving around.

How can I spin it with the A/C on if it is already spinning on its own?

This whole fan problem is driving me crazy!


Thanks again guys,


Carlen

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1987 560SEL (210,000 miles)