Electric Aux Fan Wearing Out? - PeachParts Mercedes-Benz Forum

emerydc8 · #1 06-10-2007, 07:34 AM

Does anyone know if the MB electric aux fan motors weaken with age? I noticed that it is fairly easy to slow my fans down significantly, when they are operating in low, by just putting my hand around the front hub and applying pressure.

I've heard that an "unofficial" test for the viscous fan clutch is to carefully stick a rolled up newspaper in the fan blade while it is running and hot. If you can manage to get the fan to stop or slow significantly (without injuring yourself, of course), the clutch is worn. If the fan shreds the paper and keeps going, it is probably okay.

I was wondering if there is any quick and dirty way to see if the electric fans are worn. After over 230,000 miles in the Arizona desert, I'm wondering if replacing them would improve cooling capacity for the summer.

I replaced my radiator about 100,000 miles ago and I've flushed it out regularly over that six year period. I think it's still okay. I just replaced the thermostat and water pump too. I noticed, however, that while idling with an outside air temperature of 72 F, once the high fans came on (I have the Cool Harness modification that sets them off at 92 C coolant temp), the fans (and maybe the radiator) are not capable of getting the temperature back down to the point where the high fans should normally turn off (I think that is about 85 C with the Cool Harness). The coolant temp seems to stagnate right above that point (around 85-87 C) and never cools lower than that, unless I drive the car. This occurs with the a/c on or off. BTW, with the a/c on, the vent temp was running a steady 39-40 F at idle.

It's no big deal, and I probably wouldn't have noticed it at all with the normal 105 C trigger for the high fans. But I was curious as to whether the efficiency of the cooling system could degrade with wearing aux fans and, if so, how can one determine whether they are worn.

Any thoughts?

lee polowczuk · #2 06-10-2007, 09:08 AM

i don't think the radiator test applies to the aux fan test.

i just replaced my aux fan at 209k.... it was drawing too much current and blowing fuses at the high fan speed.

then it started making an awful noise like bearings were going out....

i have the single fan system..pretty easy to change out... 15 minutes out..and probably 25 minutes back in... i took one bracket bolt out that i didn't need to..and it was a bear putting back in..

Arthur Dalton · #3 06-10-2007, 10:09 AM

When you have modified the cut-in as low as 92C , you can not get to a cut-out when you are running NORMAL temps.
92C is too low for aux fan in normal climates , but you are in extreme climate, so I assume that is why you have gone that far...You have gone from 105/107 to 92..don't even expect a cut-out. The thermo doesn't even open until 80C.

..

emerydc8 · #4 06-10-2007, 10:15 AM

And the 80 degrees will never be seen if the car isn't moving.

Arthur Dalton · #5 06-10-2007, 10:17 AM

Correct.

mespe · #6 06-10-2007, 10:40 AM

Alot of times you can take the fan apart and clean the bearings,,, lots of crud gets caught in there and makes the fans turn slowly. I used brake cleaner to clean the bearings out and then repacked them with a little axle grease.

JimF · #7 06-10-2007, 11:20 AM

If your car is in a hot climate, then IMO, there's three (3) things that must be working 'properly';
1) the radiator must be fully "open" so that the entire internal "network" is used so that the returning coolant is as 'cool' as possiblel.
2) the tstat should be fully operational (80C tstat recommend).
3) The Aux Fans (A/F) are operational.

Additionally, the VFC should be operational. Most are not b/c if it's like mine, it doesn't cut-in until above 100C. So it's not much use at lower (90C) engine temps.

A/C off:
Even in a 90F climate it's possible to keep the engine temperature around 85 to 90C. I do it in my W140 cpe with no problem and it's 13 years old.

The coolant mixture is set to 35/65% with the use of MB af and distilled water. The last item is a must! You can "get away" with tap water for awhile but as the radiator ages, you will see higher operating temps, plain and simple. If your rad is partially plugged you WILL see higher engine temps. If you use tap water, you will see higher engine temps as it ages. Additionally use a coolant additive does help remove heat from the coolant very effectively.

My A/Fs do not come on until 94C is reached (on the temp gauge). And they normally do not come on in stop-go driving primarily due to to 1) + 2) plus the 35/65% ratio. The engine temp stays between 85 - 88C w/ no A/Fs.

Now if we consider A/C being on, then, of course, the A/Fs will come on simply due to "pressure"; if it exceeds 14 bar (practically speaking, 15 bar), the A/Fs will come in low speed independent of the engine temp.

Once the A/C is on the engine temperature is now 'stepped-up' but still not above 85 - 90C for my car. So the A/F will cycle as they should. Of course, ambient temperature plays a big part here; if it's 95F day, the A/Fs WILL run in stop-go traffic; will not run during highway driving if your radiator is working properly.

A/F 'wear-out': If they don't turn. . . it's normally that the brushes are worn and don't make contact. A "tap" on the front has temporarily fixed many A/Fs. Yes, you can slow them with some hand pressure.

For my car w/ a Cool Harness (CH-92), the fans start at 94C which is a typical start temp. Since, even in a warm 85F day, the fans do not come on (no A/C) primarily because of 1), 2) and 35/65% ratio plus the use of a coolant additive.

"80C will never be seen if the car isn't moving": MB states that the minimum operating temperature to meet 'specs' (emission, etc) is 80C. You would NOT want your engine to operate at that temperature, period. I believe that 85 - 90C is ideal for that.

Palangi · #8 06-10-2007, 11:45 AM

Quote:

Originally Posted by mespe

Alot of times you can take the fan apart and clean the bearings,,, lots of crud gets caught in there and makes the fans turn slowly. I used brake cleaner to clean the bearings out and then repacked them with a little axle grease.

I can't find it at the moment, but there is an ancient thread where someone wrote up replacing the aux fan bearing. I think it was on a 123 or 126.

emerydc8 · #9 06-11-2007, 01:28 AM

Thanks. I'm running 35%/65%, but I've used tap water instead of distilled water. I'm also using Prestone instead of MB coolant. Is there really a difference? If so, I'll make the change.

I love the Cool Harness, Jim. It works just as advertised and I haven't seen the coolant temp above 100 C yet--even though it's already reached 102 F here in Arizona; so, even though the fans tend not to shut off once they come on, they do keep the temp from getting above 100 C.

I thought about taking the car in to have the radiator flushed at a radiator shop, but I've never done this and I'm not sure whether it really does much, versus the more expensive option of replacing the radiator outright. Has anyone had any experience with a professional radiator flush? Can a professional radiator shop do much more than the flush available at Autozone?

JimF · #10 06-11-2007, 10:39 AM

Quote:

Originally Posted by emerydc8

Thanks. I'm running 35%/65%, but I've used tap water instead of distilled water. I'm also using Prestone instead of MB coolant. Is there really a difference? If so, I'll make the change.

If you have 230K miles on the radiator that has used tap-water, I can almost guarantee that it's partially plugged and/or the passages are not a wide as they were when new.

Quote:

Originally Posted by emerydc8

I thought about taking the car in to have the radiator flushed at a radiator shop, but I've never done this and I'm not sure whether it really does much, versus the more expensive option of replacing the radiator outright. Has anyone had any experience with a professional radiator flush? Can a professional radiator shop do much more than the flush available at Autozone?

I would try the flush. . . what have you got to loose?? If you see a lot of 'stufff' coming out, then maybe it's time for a new radiator. Personally never had a 'pro' flush so can't comment.

As far as use of af, I have used Mercedes af + distilled water and it does what it says. But I'm not sure that there isn't other brands that are as good. But distilled water has NO substitute.

Had a good friend who's MB was running as you described; car had 110K on the original radiator that saw only tap-water. While "playing" with the VFC, he broke the "nipple" on the top of the radiator that goes to the overflow bottle. Once that has been broken, there's no way to 'repair' it. So he bought a new radiator. Now engine temp "NEVER" goes above 95C w/ AC on in 90F weather. That opened my eyes.

So if the 230K miles are on the original radiator, it may be time. However, make sure it's not something 'dumb' like a partially stuck tstat; ie one that won't fully open.

emerydc8 · #11 06-11-2007, 12:36 PM

So many parts to change; so little time and money to do it. I'll wait until it really gets hot here (118 degrees) and see how it works. If it spends too much time above 95 degrees, then I'll change out the radiator and be done with it. Thanks. Any advantage with an 80 C thermostat vs. 85 C?

Arthur Dalton · #12 06-11-2007, 12:44 PM

I would clean the radiator/condenser outside fins with soap/water ..you can aslo seperate them a bit and get the dirt in between,, you will be surprised at how dirty the fins get. and how the airflow will improve with a simple cleaning...for no $$$$.
Dirty fins cut the effieciency of both quite a bit.

JimF · #13 06-11-2007, 01:05 PM

Quote:

Originally Posted by emerydc8

So many parts to change; so little time and money to do it. I'll wait until it really gets hot here (118 degrees) and see how it works. If it spends too much time above 95 degrees, then I'll change out the radiator and be done with it. Thanks. Any advantage with an 80 C thermostat vs. 85 C?

I changed an 85C temp a few years ago (it wouldn't fully close) so the car took a long(er) time to warm up. Replaced it with a 80C version.

Quote:

Originally Posted by Arthur Dalton

I would clean the radiator/condenser outside fins with soap/water ..you can aslo seperate them a bit and get the dirt in between,, you will be surprised at how dirty the fins get. and how the airflow will improve with a simple cleaning...for no $$$$.

Great point! In fact if you want to try having the radiator "professionally" cleaned, then while it's out, you can clean and blow out the 'stuff' that's in there and in between the AC condensor (stuff in between the cooling tubes also) and radiator.

Arthur Dalton · #14 06-11-2007, 01:16 PM

I used to do commercial refrig and we had a liquid condenser cleaner that was applied to a warm condenser [ squirt bottle] and let to sit for 15 min.... it would turn to a heavy foam and then you just rinsed it off with hose/warm water..does a great job ..they have to Breathe.
But any good detergent and hose flushing will do.
I have seen some guys use pressure washers , but be real careful here b/c the trick is to hit the fins straight on..if you accidentally let the pressure hit them from any angle at all, you will bend the fins over and wind up with resticted airflow...no good.

myarmar · #15 06-11-2007, 08:46 PM

I have two fans set up on W140 and pass. side fan was making noise and did not spin as easy as driver side fan. According to WIS, to remove the fans on W140 radiator and condenser have to be removed with the fans as an assembly. That would require freon recovery and recharge. I did not want to do that.
What I found was that fans could be taken out without disturbing condenser and radiator. There are a few small bolts hard to access, but still better then WIS process. Also the fan shroud needed to be trimmed in the lower driver side corner to clear condenser feed line.
When the fans were removed I found a big pile of leaves, dead bugs, etc. behind and below pass side fan. This pile was covering about 10 - 15% of the condenser area, and not visible from outside. So do clean your condenser!
As for the fan, I lubricated outside bearings with a few drops of ATF. That made it spin better for now. The inside bearing is not accessible without full disassembly. I'd wait for the cold weather when car can live with the single fan and then try to take bad one apart and see if it could be fixed.
Mike