How do I check fan clutch? - PeachParts Mercedes-Benz Forum

wayne2970 · #1 10-04-2002, 05:18 PM

I am having a problem w/ my 1992 300D
running hot.

Temp climbs while idling and afer a hard run.
Sometines to 110 degrees.

replaced cap, thermostat, and coolant, seems alittle better.

With engine @ 100-105 I can reach in and stop the fan cluch by hand w/a towel

1. whats the acceptable operating temperature range?
2. when do the aux fans come on( passenger side fan doesn't seem to come on often) ?

Wayne

ILUVMILS · #2 10-04-2002, 06:04 PM

Hi Wayne It's possible that your problem may be a combination of things. I've seen partially clogged radiators that don't let enough heat thru to the fan clutch. It's easy to check for a clogged radiator( no tools req'd ). With the engine at operating temp, hold it at about 3000 rpm for a minute or two then let it return to idle. Shut the engine off immediately and reach in between the fan and the radiator. If the center of the radiator is barely warm or even cool to the touch it's clogged. In that condition it won't let the viscous fan clutch heat up so it's like having no fan at all. I know it sounds scary but it works! As far as your auxiliary fan goes, both fans should work at the same time. It probably has a two-stage setup. The first stage( lower speed) comes on with high engine temp. The second stage( high speed) comes on with high A/C pressure. One other thing to keep in mind. Diesel models usually have insulated encapsulation panels beneath the engine and transmission. If you remove these in the summer it will probably lower the temp a bit. My guess is that you'll need a radiator and a fan motor. Let me know how it goes.

jsmith · #3 10-05-2002, 08:34 AM

there was a post recently that if you spin it hard by hand, it shouldn't go more than half a revolution...

#4 10-05-2002, 11:33 PM

I've got to add my .03 cents here (inflation). Last year I too had cooling problems that were kicking my butt. The viscous fan seemed fine, no noticeable fore and aft play, resistance while spinning it, overall I dismissed it as being a problem. UNTIL........

I got the engine to operating temperature, shut it off and started my usual looking at everything and going into deep thought (I'm sure everyone has done this at least once while staring at your engine).

Anyhow, I reached down and grabbed the fan and moved it fore and aft, you wouldn't believe how much play I had in the clutch (after the engine was hot). It looked fine and felt fine when cold, but when it was hot is when all of the play showed up and I was able to pinpoint it as being the problem.

Try that and see what you've got if you haven't already.

Dale

MikeTangas · #5 10-05-2002, 11:42 PM

And please, please, please DON'T EVER TRY TO GRAB A SPINNING FAN with your hand. Real easy to lose a finger or two, or a whole hand. I don't care if your hand was wrapped in a towel, that just allows for something else to get caught in the belts & pulleys.

Keep it safe!

jsmith · #6 10-06-2002, 12:32 PM

wait a minute, it's supposed to free wheel at normal operating temps right? mine spins after the engine is warmed up. i've never seen it locked before though because getting temps around the engine to around 107F is hard to do unless it's midsummer (plus i have the cooling harness)...

JimF · #7 10-06-2002, 08:13 PM

you will never see it operate in your lifetime. The temp of the bimetallic strip (bms) is set to high to active the vfc at 'normal' temps.

You can remove it easily (see Menu #19) and see the temp tests (menu #20). But if by inspection, the bms looks the same, don't waste your time.

The 'mod' described in #19 will force it work. It does work well.

wayne2970 · #8 10-07-2002, 07:16 AM

How nuch noise is generated when you modify the clutch and can you still modify if the clutch has alot of play.

Thanx for your input...

JimF · #9 10-07-2002, 10:38 AM

and it's like the loud air rush. In my car, with the doors closed, you really can't hear it. At idle, it's not detectable.

re 'play': I'm not sure what lot's of play 'looks and feels like? Is it an eccentric side-to-side play?

My tech gave me a relatively new unit that was removed from a car, so it had no 'play'. My old unit (about 100k) didn't seem to have any play.

pentoman · #10 10-07-2002, 12:48 PM

To test if the fan clutch is engaging:

overheating troubleshooting 84 190E

jsmith · #11 10-07-2002, 12:56 PM

it's the viscous fan clutch that is being discussed. it's a mechanical component that is heat activated...