W124 overheating / cooling fans? - PeachParts Mercedes-Benz Forum

yosshimura · #1 11-02-2005, 06:41 PM

Its nice not to have to post often in the tech area , which means no problems

.....

Anyway, I have seen my temp gage max out 2-3 times recently when idling for a few minutes (ie drive through at fast food). I read through the archives and I think it might be the fans.

Here is the scenario:
- 95 W124 / new water pump & hoses about 9K miles -5 mths ago / 110K miles
- WHile driving you would not have a clue of the overheating, needle is pegged at midpoint.
- Today, I noticed , after one of these "high temp" episodes that only oneof the two fans up front was spinning. Is this right? Or are they both supposed to run at once? Makes a little sence, since when the car moves temp goes back to normal.

Once I figure out if these dual fans are supposed to run simmulanously (sp?) I can either discard that as being the problem or address it. What is the correct name for these fans?

Thanks

Arthur Dalton · #2 11-02-2005, 08:32 PM

Both fans are wired in parallel, so they both work together..
Spin the non working one to be sure it is not blocked by a stick/etc.. it is probably bad...

sydney · #3 11-02-2005, 10:54 PM

Have you already ruled out the fan clutch as it is the device that engages the radiator
cooling fan as the engine becomes hotter. I think the electric fans are related to the air
conditioning. The fan clutch is a commonly replaced item. You should be able to
hear a change in the amount of air blowing when it is engaged. It should be engaged when
the engine is cold and will release after running for a short time like 30 seconds or so and
it should also then engage when the engine is hot. This is not to say you may not have other issues , but the fan clutch is definately related to cooling when the temperature
rises.

yosshimura · #4 11-03-2005, 01:39 AM

Quote:

Originally Posted by Arthur Dalton

Both fans are wired in parallel, so they both work together..
Spin the non working one to be sure it is not blocked by a stick/etc.. it is probably bad...

We have a problem b/c when I noticed the passenger side one wasn't spinning today, I moved it and it just spinned without any hesitation with the push of my hand, while the other one was going full force... so even though in parallel only one is working

While in these episodes the a/c stops cooling, which obviously is tied to eng temp...

RAYMOND485 · #5 11-03-2005, 02:13 AM

1984 300d Turbo 135k
Engine Hot, Turn Off Engine, Move Fan By Hand If Loose Replace
Fan Clutch $160.00

Arthur Dalton · #6 11-03-2005, 03:25 AM

Quote:

Originally Posted by yosshimura

We have a problem b/c when I noticed the passenger side one wasn't spinning today, I moved it and it just spinned without any hesitation with the push of my hand, while the other one was going full force... so even though in parallel only one is working

While in these episodes the a/c stops cooling, which obviously is tied to eng temp...

The fan motor itself is at fault [ probably brushes, as you have verified the bearings are not locked up by hand spinning ]...
The a/c has a high pressure switch that will cut the compressor in the event that the high side pressure has reached a danger zone caused by high thermal load conditions, which is exactly what a non operating aux. fan will create. These two fans are activated by high coolant temp for the high speed and a/c high side pressure for the low speed. Either activation requires both fans to run at the same time, regardless of which system is being called for.
Fan motor should be replaced.

justino · #7 11-03-2005, 05:43 AM

I had a similar problem on a 1991 300e 4matic in the UK, 205,000 miles

When I bought the car it would overheat quickly, and max out when stationary. A new thermostat (very cheap and quick to fit) cured that problem immediately.

During the diagnosis of this I noticed that neither of my 2 electric auxillary fans worked. I managed to get one slowly back into life by tapping the centre spindle lightly with a small hammer. Following this I drilled a small hole into the plastic cowl which covers the centre of the fan motor and filled this with WD40 spray lubricant using the straw that comes with it. Shorting out the temp sender I let the fan spin for 5 mins to free it self up. You may wish to silicone up the small hole once all is well.

However this method hasn't worked on both fans, but is worth a try as a temporary fix. I think the power lead may have become detatched from the other, and it's not easy to get access to.

In any event with the new thermostat the car doesn't get hot enough to turn the fans on (105 degrees I think) and my aircon is out of gas which is the other trigger for turning them on.

Michael K · #8 11-03-2005, 05:47 AM

When did the problem start, right after the new water pump or later?

optimizer · #9 04-19-2009, 12:23 AM

Ok I know this thread is 3 years old, but no point in retelling my story since it's almost identical... lol...

So here it is: W124, 1993 300CE (pre-facelift)

- Replaced thermostat
- Replaced fan clutch
- Cooling fans occasionally turn on 66% of the time both turn on when engine reaches around 105 deg. If they don't turn on I can just give them a quick tap and they will turn on.
- In stop and go, or idling traffic, engine will quickly rise to between 100 - 110 deg
- Cruising, engine will hover around 90 - 95 deg

So at this point, does a water pump or radiator replacement make sense? Is there something simpler? Thanks

Arthur Dalton · #10 04-19-2009, 12:30 AM

< In stop and go, or idling traffic, engine will quickly rise to between 100 - 110 deg
- Cruising, engine will hover around 90 - 95 deg

>

With or without A/c ON ???????

optimizer · #11 04-19-2009, 01:38 AM

Quote:

Originally Posted by Arthur Dalton

< In stop and go, or idling traffic, engine will quickly rise to between 100 - 110 deg
- Cruising, engine will hover around 90 - 95 deg

>

With or without A/c ON ???????

without a/c on...

Arthur Dalton · #12 04-19-2009, 12:26 PM

OK

Try this test,
On the a/c drier there is a pressure sw with a 2 wire pigtail. Slide the sleeves back on the connectors and jumper wire those two wires
That should give you low fans.
If YES, then try the car in traffic and idle and see where the temp gauge registers.
Regardless , you still want those both fans to be fixed.............

optimizer · #13 04-19-2009, 02:55 PM

thanks - ok sounds easy enough so if having those fans on permanently on low seems to keep the temp low then what would be the actual long-term fix?

optimizer · #14 04-19-2009, 04:28 PM

ah gotcha... cleaning the rad should be relatively straight-forward

another question... when you say condenser are you referring to the AC condenser or something else? I tried googling pics and all I got were AC condensers. If it's the AC condenser, how do I get to trying to unblock an AF issue here?

Arthur Dalton · #15 04-19-2009, 04:34 PM

Listen

The ac cond has fins...the ac cond is in FRONT of the radiator...if the fins of the cond are full of dirt and debries , then the air can not get to the radiator..see?
So , the rad has a problem cooling b/c it has rstricted air flow.
That is the gest of it.
The ac cond gets cleaned with a garden hose and soap spray..just like you would clean your house ac unit. Then , you can seperate the rad and cond on top a bit and look in between the two for debries and leaves and such...they inhibit flow ..it is that simple.