viscous coupling

[bennesspipers]

Anyone know how i can test if the viscous coupling on my W202 C220 is doing its job correctly ? I ask because iv recently changed the water pump & changed the engine oil, left it running for half an hour, & when i came back to it the temp was nearly on 100, took it for a ride & it soon cooled down, but im wondering why it got that hot in the 1st place.

 

[MBK]

Hi,

Try and spin the fan when engine is cold, should spin easily. Then get the car up to temp 90 - 100c switch the engine off, wait for fan to stop spinning, then try and turn the fan if the coupling is working then the fan should now be harder to turn as the coupling is engaged. This should give you an idea of whether you need a new coupling, by the way to change the coupling on a 220 engine is very simple, i done it and posted a thread on here on what tools i used and a basic how to. I'll search for it and paste a shortcut.

K

EDIT:LINKY

 

[bennesspipers]

Thanx MBK, iv already had it off,just changed the pump, try your tip now.

 

[grober]

Remember the large nut has a lefthand thread!

edit just read you already had the coupling off when you removed the pump!

 

[bennesspipers]

Just had it up to 88 degrees,stopped, fan still loose. So it appears the couplings not working !

 

[lynall]

Another way is to get engine good and hot and with it running try to stop the fan with a rolled up newspaper.
I have had to replace viscous on mine and the wifes old e320 they were both doing the same as yours.



Lynall

 

[kth286]

Not hot enough yet.

Looking at the Merc workshop manual for 202 it says that the fan cut in temp is 102 to 110 degrees.

Run engine at fast speed and once the coolant temp has reached above figures you should hear the loud noise from the fan coupling as the fan speeds up.

 

[Ali E300TD]

Oil was leaking from visco on my E300TD 98. I changed it with a brand new acm unit.

But it still goes to 90-95 deg when its around 45 deg outside... is it normal?? Or is there something else wrong with my engine?

 

[grober]

Just had it up to 88 degrees,stopped, fan still loose. So it appears the couplings not working !

Make sure the bimetal strip sensing/control assembly at the front of the coupling is not choked with road debris/oil/gunk preventing it from working properly. A old tooth brush+wd40 is a good cleaning combination [ CAREFUL its a delicate mechanism]. If you get a new one make sure its been stored vertically since resting horizontally allows fluid to migrate to places it shouldn't be and malfunction of the coupling.

 

[bennesspipers]

Iv removed it ,placed in a pre-heated oven @ 125 degrees, & its still loose. Good news is iv found a new one on e-bay for £30 inc p+p ! (For those of you who are married, WAIT FOR THE WIFE TO GO OUT before you use her cooker ! )

 

[kth286]

Iv removed it ,placed in a pre-heated oven @ 125 degrees, & its still loose. Good news is iv found a new one on e-bay for £30 inc p+p ! (For those of you who are married, WAIT FOR THE WIFE TO GO OUT before you use her cooker ! )

Whoops !

Whilst the fan should cut in at a coolant temperature around 102 to 110 degrees THAT IS NOT the fan temperature.

The fan senses air temp behind the rad and the bimetal strip alters it's shape and opens the valve at approx 71 degrees (air temp).

 

[lynall]

Make sure the bimetal strip sensing/control assembly at the front of the coupling is not choked with road debris/oil/gunk preventing it from working properly. A old tooth brush+wd40 is a good cleaning combination [ CAREFUL its a delicate mechanism]. If you get a new one make sure its been stored vertically since resting horizontally allows fluid to migrate to places it shouldn't be and malfunction of the coupling.

Ive always said this very same thing to people but, whenever i go to the stores to get a new viscous for a truck they are stored however they come in the box.

Plus surely they are not stored permanently upright when being made and transported.

Even when new my car one was not very stiff but straight away the temp was lower and i felt much happier sitting in heavy traffic.



Lynall



Lynall

 

[Ali E300TD]

Oil was leaking from visco on my E300TD 98. I changed it with a brand new acm unit.

But it still goes to 90-95 deg when its around 45 deg outside... is it normal?? Or is there something else wrong with my engine?

Can anyone reply to this as well?

 

[grober]

Can anyone reply to this as well?

First the water in the coolant system doesn't boil at 100c as normal because its under pressure [ABOUT 1.5 BAR] which raises the boiling point to quite a bit above normal.[Up to 130C] The sensing element on a viscous coupling is the bi metal strip at the front which moves a actuating pin allowing the silicon based viscous fluid to flow into a chamber to a varying degree coupling the drive to the fan. When engaged it will of course use some engine power to drive it effecting economy. Its calibrated NOT to come on over the normal temperature range of operation of the engine but SHOULD progressively engage over the coolant temperature range 96-110C It also has a safety cutout which operates at 4,500 rpm engine speed corresponding to a fan speed of 3250 since it never completely catches up with the engine speed.

 

[Ali E300TD]

So grober you mean to say its normal....?

 

[lynall]

You will see when you fit the new fan.

Mine was fine when running but hit traffic when warm outside and the temp would creep up towards 100, which whilst apparently inside mb parameters i wasnt happy with so new coupling fitted and now sits 85 rock solid everywhere.

This is also exactly how wifes old e320 m104 behaved until new coupling fitted.

So old fan was working just not properly and i would say yours is/was the same.

As for the guys e300 running hotter he did say 45 deg c outside temp and thats bloody hot hot, so is probably okay.



Lynall

 

[bennesspipers]

Thanx for that info Lynall, should arrive in a day or two, old one looked just that, OLD ! so im sure its all to the good.

 

[smick]

Just to let you know the packaging on my new visco does have arrows to indicate how it is to be stored.So I think your onto something. thanks.

 

[detomaso]

Pants, I think something similar may be happening with mine. I've just changed the coupling on my w201 this weekend and all seemed fine though I did think it odd that the fan was spinning quick along with the engine revs when cold, but this stopped after a mile or so once the engine had warmed up a bit (???) and I couldn't hear the fan. Did a couple of tests by purposely sitting in traffic and hearing the fan get louder then dropping away as it cooled down and disengaged but today when traveling back from work it was engaged all the way home. I've just done a twenty mile route to test again and it is still doing it. The temperature is about 85 all the time and I just had a little push of the fan after stopping the engine and there is some resistance. Do you think my new coupling has failed due to not storing it properly, I have had it lying flat in its jiffy bag for a week before fitting it...

I will check in the morning how little resistance there is.

 

[lynall]

I am still not convinced by the storage thing like i said in my earlier post the truck fan hubs are stored any old how and they are £840 each and if it was that important they would defo be stored upright.

Plus if it was posted to you it could be in any position possible as parcel man wouldnt keep it upright would he?

Sounds like it was working correctly, as in cutting out after a mile when cold and maybe still is ie have you an engine problem which the fan is trying to keep under control?



Lynall