2003 viscous fan is always quiet. Not kicking in?

Jiberfish

New member
My engine has had overheating problems on long uphills on hot days. The temp will rise to about half way been the 215 and red line marks. ( Around 230-235 degrees) I've heard the aux fan kick in, but never noticed a difference in the viscous clutch kicking in. Its always spun. Tried to stop it when hot and it spins strong. But I've never noticed it kick in loudly when under load like I've seen people say on the forum. I replaced the clutch and no difference. Changed thermostat, radiator cap, flushed coolant and cleaned between the radiator stack. Then I thought maybe it was the serpentine belt or tensioner. Changed the serpentine belt and the newer one was certainly tighter than the old one. And the tensioner took quite a bit of strength to release the tension, so it seems strong. However, yesterday on a long uphills it still rose to about 230. Any ideas what it could be? Next thing I can think to change is the belt tensioner. It's an $80 part and id like to not keep throwing money at the problem with no improvement.
 

220629

Well-known member
The Electric Fan is programmed to kick on at 221F engine temperature.

If you skim down through this thread rkymtn outlines the tests that he did.


After all of the comments in that thread, my take on the viscous fan clutch...

If everything else has been exhausted through testing (see rkymtn tests), but the Sprinter still isn't cooling, consider replacing the viscous fan clutch with a MB dealership boxed part. To be clear. That comment relates to the everything has been checked situation. There are many T1N Sprinters around the world running just fine using viscous fan units that didn't come in a MB labelled box. My replaced 2004 clutch has been fine. It is not a dealership part.

:2cents: vic
 

Nautamaran

2004 140” HRC 2500 (Crewed)
Having read that thread it seems there is a high initial failure rate with these fan clutches? Lots of tales there of money wasted on dead-when-new, non-returnable units. So I wouldn’t trust that the new clutch that you installed was a good part, especially if you can’t hear it grabbing. I can hear mine on 80 degree days whenever I pull away after waiting at a red light at the bottom of a freeway off ramp.

The fan clutch is triggered by the hot air coming out the back of the HOT radiator, so you’ll never hear it in rain or fog (or snow), or if your thermostat is stuck closed, or if your rad is plugged, etc. These conditions will prevent the rad staying hot enough to heat the air flowing through it.

But if the top pipe coming from your thermostat is getting properly hot (use an IR thermometer to measure it: above 190’F it should closely match your dash gauge) then your pump and thermostat are likely fine. Since your rad is recent, in your situation I would take another hard look at your fan clutch.

The belt tensioner is unlikely to cause overheating unless it has failed completely, but its condition can be assessed by looking at its plane of rotation - its pulley should be parallel to the other pulleys, not tilted; and by removing the belt and turning the pulley, which should rotate smoothly without any steps or roughness in the ball bearings. The spring pivot must also move smoothly as you compress the tensioner to put the belt back.

-dave
 

Jiberfish

New member
The Electric Fan is programmed to kick on at 221F engine temperature.

If you skim down through this thread rkymtn outlines the tests that he did.


After all of the comments in that thread, my take on the viscous fan clutch...

If everything else has been exhausted through testing (see rkymtn tests), but the Sprinter still isn't cooling, consider replacing the viscous fan clutch with a MB dealership boxed part. To be clear. That comment relates to the everything has been checked situation. There are many T1N Sprinters around the world running just fine using viscous fan units that didn't come in a MB labelled box. My replaced 2004 clutch has been fine. It is not a dealership part.

:2cents: vic
Tested rad hose temps and the thermostat and pump seem to work fine. Gauge is accurate.

Having read that thread it seems there is a high initial failure rate with these fan clutches? Lots of tales there of money wasted on dead-when-new, non-returnable units. So I wouldn’t trust that the new clutch that you installed was a good part, especially if you can’t hear it grabbing. I can hear mine on 80 degree days whenever I pull away after waiting at a red light at the bottom of a freeway off ramp.

The fan clutch is triggered by the hot air coming out the back of the HOT radiator, so you’ll never hear it in rain or fog (or snow), or if your thermostat is stuck closed, or if your rad is plugged, etc. These conditions will prevent the rad staying hot enough to heat the air flowing through it.

But if the top pipe coming from your thermostat is getting properly hot (use an IR thermometer to measure it: above 190’F it should closely match your dash gauge) then your pump and thermostat are likely fine. Since your rad is recent, in your situation I would take another hard look at your fan clutch.

The belt tensioner is unlikely to cause overheating unless it has failed completely, but its condition can be assessed by looking at its plane of rotation - its pulley should be parallel to the other pulleys, not tilted; and by removing the belt and turning the pulley, which should rotate smoothly without any steps or roughness in the ball bearings. The spring pivot must also move smoothly as you compress the tensioner to put the belt back.

-dave
Dave, thank you for the reply. Your information is a huge help and it's encouraging you also suspect the clutch. I looked on europarts SD and it looks like the clutch I received is an ACM Germany branded part. They also sell a whole assembly with fan installed that is genuine Mercedes and then a febi Bilstein branded one for about $30 less. Any idea where you can get a genuine Mercedes clutch without the fan or is the Bilstein worth a shot? Thanks again.
Andrew
 
B

billintomahawk

Guest
Remove fan and add some of this it’ll roar when it locks up! The silicon oil they put in them is shit house!!!
I'll bite since I have no idea how the damn thing works, how it can be shipped upside down and then come to life when put in service for the first time.

Are you saying we can 'change' the oil in them?

Maybe we should boil them first before installing.

Has anyone cut a failed on open?

And let the magic out.

bill
 

trc.rhubarb

Well-known member
I'll bite since I have no idea how the damn thing works, how it can be shipped upside down and then come to life when put in service for the first time.

Are you saying we can 'change' the oil in them?

Maybe we should boil them first before installing.

Has anyone cut a failed on open?

And let the magic out.

bill
Maybe this helps a little:
 

trc.rhubarb

Well-known member
Also, skip to about 14m in
 

220629

Well-known member
I'll bite since I have no idea how the damn thing works, how it can be shipped upside down and then come to life when put in service for the first time.

Are you saying we can 'change' the oil in them?

Maybe we should boil them first before installing.

Has anyone cut a failed on open?

And let the magic out.

bill
Someone already asked the same questions here.



vic
 
B

billintomahawk

Guest
Someone already asked the same questions here.


It was almost a year ago. They probably forgot about the replies.

vic
Haha Vic, But he didn't get an answer? anyway I do remember but I still don't understand why why why I can't lay the damn thing flat, that makes no sense to me?

I'm not being dense, I just don't get the why therefore for me the thing is either still the realm of magic or the need for vertical storage is incorrect.

bill
 
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Flyingquincy

New member
I can’t help but suggest that if you have a known “dead fan” that you physically lock it up (tek screw has been used previously) and see if cooling is improved. Yes it will roar as it it running flat out all the time but it’s another thing to eliminate.
 
Pull it out undo the bolts holding the fan on then the bolts holding the halves of viscous hub together. split it shaft side up empty out the burnt shitty old silicone oil. Give it a good wipe out then some brake clean loving, about half fill the reservoir with new silicon oil like the one i listed above (i like 10000cst but 8000 to 20000 will be fine higher the number the more viscous and harder it'll hook up) in the part with out the shaft, hold vertical and see if it spills out the hole in the centre if not add more till its just shy of spilling out. lay flat on bench and reassemble the hub, fan and reinstall. Crack a beer and call it good.
 

marklg

Well-known member
Tested rad hose temps and the thermostat and pump seem to work fine. Gauge is accurate.



Dave, thank you for the reply. Your information is a huge help and it's encouraging you also suspect the clutch. I looked on europarts SD and it looks like the clutch I received is an ACM Germany branded part. They also sell a whole assembly with fan installed that is genuine Mercedes and then a febi Bilstein branded one for about $30 less. Any idea where you can get a genuine Mercedes clutch without the fan or is the Bilstein worth a shot? Thanks again.
Andrew
Febi and genuine Mercedes are nothing like each other. I think Mercedes only sells the combo as an unbalanced fan can wreck the viscous clutch.

IMG_20200901_071436_copy_900x675.jpg

Genuine on the left. Febi on the right doesn't work well after a year.

Although I did not start out thinking this way, I've installed two aftermarket clutches, one noname and one Febi Bilstein that haven't worked out. I spent way more than if I had just bought the genuine one the first time.

Regards,

Mark
 
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220629

Well-known member
Haha Vic, But he didn't get an answer? anyway I do remember but I still don't understand why why why I can't lay the damn thing flat, that makes no sense to me?

I'm not being dense, I just don't get the why therefore for me the thing is either still the realm of magic or the need for vertical storage is incorrect.

bill
There was an answer.

...
:idunno:
Not an old wives tale to me.

The old "they shipped it to me flat" argument often comes up. My theory is that when they are manufactured the clutch units have the fluid trapped in a certain section/area of the assembly. Once the clutch is installed, the operating temperatures cause the fluid to be released to do the job as designed.

I have seen where fan units that were laid flat needed to be replaced because they no longer worked properly. Was it being laid flat, or was it just being disturbed that caused the problem? I can't answer that, but I still stow the fan assembly upright when removed for repairs.

There are those who replace leaked fluid. The replacement clutch units aren't so expensive as to tempt me to research the refill procedures.

:2cents: vic
During shipment the fluid is trapped by the thermostatic valve seal [aka pin seal] to stay in the correct place. After the clutch is installed the engine heats up, the valve opens, and the fluid is distributed by centripetal forces out into the proper chambers. Once the fluid is distributed the clutch unit can no longer be laid flat.
*****
Added:
The condensed Sachs brand text that I provided is:

"It is most important that the fan clutch be positioned correctly during transportation and storage. Please note the arrow on the fan clutch package. The fan clutch should be stored either vertically but preferably flat with the arrow pointing up. This is to ensure that silicone oil does not leak past the control pin seal. Should a small amount of oil leak past the control pin seal due to incorrect storage, the fan clutch will still perform correctly."

By extension a large amount can matter. Why take the chance?
*****

MWD brought up a valid point. Some of the infant mortality or clutch never worked properly may be related to the seal leaking. Temperature extremes or altitude changes may create enough pressure to let the fluid out during shipment.

Just my understanding of the situation. I'm certain a search will reveal professional/expert opinions.

:2cents: vic
 
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JCramer

2019 MB Sprinter 3500 Coachmen Galleria
FWIW, I just drove my 3500 out to Colorado in August. I have a bluetooth OBD and use an 8" pad to monitor and watch my temp gauge, engine load %, rpm's, etc., pretty closely. On several occasions I was climbing passes over 11,000 ft with the air temp in the 95 degree range. My van usually temps around 194 up to 204. On these occasions, it would climb as high as 226.4, never higher...and that made me nervous. I did not want to overheat on a 6% grade with nowhere to pull off. I found that if I down shifted, typically to 3rd or 4th gear, slowed until the engine load was around 80% and tach'ed between 2800 to 3000, the temp gauge would drop down to about 214 and stay there. This usually brought my speed down to 45 to 55mph depending on the steepness. If I didn't have the OBD monitoring system I could not do this. FWIW, I felt it kept me from stressing or tearing up my engine. I am not an engineer or engine guy, just trying to dumb it down for me. Maybe I am fooling myself, but those steep hills on a hot day are hard on every engine on a truck or heavy vehicle.
 
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billintomahawk

Guest
"During shipment the fluid is trapped by the thermostatic valve seal to stay in the correct place. After the clutch is installed the engine heats up, the valve opens, and the fluid is distributed by centripetal forces out into the proper chambers. Once the fluid is distributed the clutch unit can no longer be laid flat.

MWD brought up a valid point. Some of the infant mortality or clutch never worked properly may be related to the seal leaking. Temperature extremes or altitude changes may create enough pressure to let the fluid out during shipment." Quote from Vic.

OK. How does it work brother?
To me.
Should the fluid or a portion of it migrate back into the center section when the unit is laid horizontal a reapplication of heat would simply reopen the thermostatic valve and the fluid would redistribute properly. Bimetalic right?
If there is one?

What am I missing? It's not a one trick pony.
Or a one way valve.
Is it?

bill
 

Jiberfish

New member
Febi and genuine Mercedes are nothing like each other. I think Mercedes only sells the combo as an unbalanced fan can wreck the viscous clutch.

View attachment 151860

Genuine on the left. Febi on the right doesn't work well after a year.

Although I did not start out thinking this way, I've installed two aftermarket clutches, one noname and one Febi Bilstein that haven't worked out. I spent way more than if I had just bought the genuine one the first time.

Regards,

Mark
Mark thank you very much for the information. Did you purchase the oem combo on europarts SD?
FWIW, I just drove my 3500 out to Colorado in August. I have a bluetooth OBD and use an 8" pad to monitor and watch my temp gauge, engine load %, rpm's, etc., pretty closely. On several occasions I was climbing passes over 11,000 ft with the air temp in the 95 degree range. My van usually temps around 194 up to 204. On these occasions, it would climb as high as 226.4, never higher...and that made me nervous. I did not want to overheat on a 6% grade with nowhere to pull off. I found that if I down shifted, typically to 3rd or 4th gear, slowed until the engine load was around 80% and tach'ed between 2800 to 3000, the temp gauge would drop down to about 214 and stay there. This usually brought my speed down to 45 to 55mph depending on the steepness. If I didn't have the OBD monitoring system I could not do this. FWIW, I felt it kept me from stressing or tearing up my engine. I am not an engineer or engine guy, just trying to dumb it down for me. Maybe I am fooling myself, but those steep hills on a hot day are hard on every engine on a truck or heavy vehicle.
I have tried down shifting, etc. But because the temp continues to rise past the 225 range, and because I've never heard the viscous fan become louder than the aux fan, I believe it is shot. What kind of scanner would work well for an 03? Ive heard the scangauge won't do much for an 02-03. My glowplug light has been staying on and I don't have a scanner to figure out which one is failing.
 

trc.rhubarb

Well-known member
@Jiberfish i have the MBII and the AP200 - id definitely get the autel. The iCarsoft doesn't seem to work for me very well while the autel is just crazy slow but works great. not as sleek as the scangauge but you could use your phone to monitor as I have.
 

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