Fan hub servicability TSB..

Fingers test:
Run engine till warm....thrust open hand into blades...loose a little skin or a finger nail before fan stops....replace hub.

Loose a finger or two...hub working as designed. :D

____________________________________________________

Lea, Marty,

Here is an attachment that shows the details of my fan clutch.

Phil

Here's some detailed answers to your questions. . .
 

Answers to your questions in the body.

If want to see the difference between your VFC and mine, all you need due is to remove your bms from the VFC and test it in water. It will bend at a lower temp than the one in my VFC, just as it does on your car. The reason is very simple; the bms was designed to bend at a lower temp because it's a different bms made with a different amalgam.

Jim

I'm sorry for questioning (I am not criticising) although I believe if one accepts things at first glance we would still be thinking that the world's flat - however I don't want to revisit that again ;)

How did you think from my comment that I don't realise that the bms raises? What I don't understand from your comments is the word 'engage'. The pin is under constant pressure from the bms which bends upwards in proportion with temperature as we all know. The fluid from within one chamber is then allowed (under centrifugal force) to exit and reach chamber two, where is locks the clutch/fan.

If you are referring to 'engage' in terms of 'the bms has moved the 1.79mm which allows engagement' then I understand. And therefore I will question anyone's test which relies on the human eye to see the this subtle movement under water due to the effects of refraction and similar difficulties.

This is why I believe Phil chose to affix his bms within a measuring instrument (albeit crude - a spark gap).

Phil destroying his vfc does have me confused too I have to say, as that would have been the last thing I would have done whilst this debate wrangles on....!! :confused: :confused:


With regards to the bms suffix A (A-GE), mine has further characters after the 77 but are a little unclear. Tonight I shall take a rag, clean the strip and take another photo to see what they are - netherless the MB part number is the same. If they have different compositions and therefore temperature characteristics how do MB differentiate?

If my bms is different we have finally solved one of the mysteries - but why would MB ship the 'tropical' version to the UK where the temperature and humidity is similar to all Europe - perhaps all Europe gets the 'tropical unit'...

???

I need to leave for work..I'll comment some more latter tonight :D

Thanks for hanging in there with me Jim, it is appreciated.

Lea

Hi Lea,

Unfortunately at the time, I had no idea that there may be a second internal bms. Had I known, I would have tried to open it up for a closer look. Oh well. Will try and locate another VFC, or two. I am now especially curious about that internal bms.

Phil

. . precisely!

It surely looks like there's no "A" after the part number as mine has. Also the color of the top metal is different; mine being brass. Not sure what yours is but it surely looks the color of the BongC36 'tropics' VFC.

I think that MB found the 119.9xx engines got TOO hot and so they modified the bms so cut in at a lower temperature. Check out this attachment for 119.974/5 engines.

Now that you have seen that 'document' (posted by Neil, KE6DCJ), we are coming rapidly to the 'very-short-strokes'! So here's two questions from me to you;
Note: abbreviations for 119 200 00 22 = "00"; For 119 200 01 22 = "01".

1) How do explain that the "00" VFC assy was designed to cut-in at 96C and this was confirmed by Ritter and me back in 2001 and again just recently? Those measurements are as the should be but 'some' are saying it should be at a lower temp. How do you explain that?

2) If your VFC is really a "00" instead of a "01", how can it cut-in at 85C??

3) Since you claim that your VFC does cut-in at 85C, how can your bms be the same as that on the "00" assy?

4) Do you think that your VFC and bms will work the same if tested in water as it does on the car?

5) If not, what possibility can be the difference? How can you explain that?

Hi Jim,

From your attachment, it is obvious that in order to lower the Fan's engagement temperature, Mercedes did indeed at some point change the VFC design for the 500E/E500.

I am curious however as to why they found it necessary to change the design of the VFC housing, and its the cover. For a much smaller cost, they could have just substituted a lower temperature rated bms into the existing VFC design, but for some reason Mercedes concluded that they needed to do more than just change the bms.

I am speculating that there was an airflow problem around the bms. Something in the original design may have prevented ambient air from adequately circulating around the bms, causing the bms to bend and engage the VFC at a much higher temperature than desired.

Any thoughts?

Phil

Phil

Yes exactly - 'looking out of the box' again - to coin a phrase I heard today! Nice work...

Why didn't Sachs simply change the bms if this is the governing factor? In fact, the tech doc regarding 974/975 engines doesn't say that they did, does it! It says they changed the identification number ;) That's my interpretation of the text.


Jim

To attempt to answer your questions (this is novel) :thinking:

Engines 960, 970, 971, 972, 980, 981 and 982 all use the '00' MB part numbers - if MB had discovered this over temperature problem they would have introduced a rolling change and 'a replaced by' part would appear in their EPC similar to their Australian models, surely? No such part replacement is visible. Also, 5 years is long enough to implement this change; as it's my understanding that the 119.975/975 only ran from '91 to '95. Note engines 980, 981 and 982 still use the '00', why don’t these use ‘01’.


LOL, sorry Jim, us Brits have no idea what 'very-short-strokes' means... :D :D

Reading back in this thread it appears we wandered off on to tstat openings, had we continued reviewing the data I was trying to present from MB doc 20-0020 we would have clearly seen that the 'design' was 92C-100C cut-in AIR TEMP. We assume 10C lost water/rad to air coupling (although this is a ‘finger in air’ delta) and we have 110C rad temp. Assuming this, stage 2 aux fans (stage 1 is never audible in my car ) cut in just before the VFC.

But, of course we assume 10C is lost in air coupling efficiency and I cannot comment much as I would guess at 10C too, but is this so?

I've shown you the pictures, there's no more I can do. Or do mean a printing error?

I've offered a couple of suggestions in my previous posts.

1. I've replaced the silicone fluid with 12,500 CST. Volume was added until the fan 'felt about right' by my mechanic colleagues (MUCH experience in automotive repair - do you guys call these 'Indies' BTW??))

By doing this I could have overfilled the chamber changing it's characteristics.

2. I don't know if it's the original fitted - although judging by its failure it probably is.

3. I've bent the bms holders and bent them back to where I thought they were - my comments about the bms being fixed and no horizontal movement were invalid (I forgot to point that out in my last post).

Yes, with differences as noted by yourself and others who have previously posted but there may also be centrifugal forces at work. My background is in electronics and so I remain cagey in detailing mechanical points, but simply want to question such that we think of all possible influences – like the plastic cage and aluminium extrusion heatsink.

4. That’s got me thinking. OBVIOUS point, I have NO black plastic cage. I removed it after my first fill and of course is why I can easily take pictures.


Some new facts about my bms - see picture attached.

The bms part number is:.... wait for it Jim.... I can see you're excited now.... :D :D :D

TB1577-GE no reference to A

How interesting and it has a M92 stamp on - year of manufacture? My MY is '92 I see yours has M94??

BUT with the same MB part number as used on the R129 model for most it's life 960, 970, 971, 972, 980, 981, 982



Out of interest I checked with Sachs' parts list for a cross reference and Sachs do indentify the 'tropical' units with separate part numbers. There’s no ‘tropical’ unit listed for the R129.



Wow.... this post hurt, but I think I'm slowly understanding....I think

I wonder if anyone else is actually bothering to read any of this garbage ?????? :ban: :ban: :ban:


I forgot to say is all this excitement, I'm going to order a new VFC from MB tomorrow so... it could get even more exciting .......

Lea

Lea,
You may be right, I re-read Jim's attachment and it could well be that Mercedes did not change the bms, but rather only the identification number.

Your other points are also extremely valid, especially the following:

==========================
"Engines 960, 970, 971, 972, 980, 981 and 982 all use the '00' MB part numbers - if MB had discovered this over temperature problem they would have introduced a rolling change and 'a replaced by' part would appear in their EPC similar to their Australian models, surely? No such part replacement is visible. Also, 5 years is long enough to implement this change; as it's my understanding that the 119.975/975 only ran from '91 to '95. Note engines 980, 981 and 982 still use the '00', why don’t these use ‘01’."
==========================

We are now much closer to solving this mystery. I see a light at the end of the tunnel. I just hope Jim does not turn the light "Off".

Regards,

Phil

Yes, they did and that was (has been) one of my points since the 'discussion' started.

The term for what you describe is called a "design deficiency" and a team of engineers, electrical and mechanical, tackle this problem from a number of aspects to find a reliable and hopefully, low cost solution to the this deficiency.

When many changes are made, it's because the data from the many engineering tests, show that ALL of the improvements were needed. Companies don't spend money redesigning 'stuff' that's not needed.

I believe I made that point a number of times in this post: and that testing in WATER is MUCH more condusive than testing in air especially in situ.

If the VFC/bms doesn't work in WATER, you can bet it needs to get much 'hotter' in air to engage. Now you are starting to see the light.

I know you keep saying that too much or too little 'gel' can cause the vfc to cut-in at a different temperature. You need to re-think that statement: the bms is the 'switch' which activates w/ temp. If the bms doesn't bend at all, there's NO VFC action. You need to drop that argument 'cause to doesn't have anything to do with the pullin point of the vfc.

I guess I need to ask you more questions in the future. Answers come very quickly it seems! ;) When I saw your picture, that's what generated my closing comment. . "don't loose that bms, it's one of a kind".

Why would you want to do that?? It's going to have a 00 bms or worse. What I would advise: your local MB dealer may have one on the shelf that you can 'inspect' before you purchase. Why would you spend $400 or more for a vfc/bms combo that pulls in at 100C.

Of course, your-one-of-a-kind bms would replace the factory version but I'd live with your old one. You can buy a lot of Toyota 'gel' for $400.

Tnx for the data; talk about VFC and aux fan cut-in points being "two hairs" apart, it certainly shows there.

Also MB can let their coolant get 123C, but I think I'll pass! Can you believe those numbers?? :(

I don't the 'problem' is any where close to being solved. Look at the excerpted 200-0020 document so as to review the "fix" for the "00" pn. MB generated the "01" pn that has the 82C bms. WRONG!

Check MENU#21 on my page, and you will see that I tested the "01" part (MB 119 200 01 22) with a Sachs number of 2100 013 032. Note the pictures of the bms show the exact same part as that in the "00" assy.

So it's a open-ended problem: personally, I've NEVER seen a low temp cut-in bms!

Jim

I have thought about this statement and still conclude that silicone viscosity may effect cut in temperature - how do YOU explain that my vfc cuts in at 80-85C then? Maybe Sachs are completely out of control in their manufacture of bms'!!! I doubt it.

My assumption is based on that the fact that the bms will bend but not much, it's transfer characteristic is linear - not bent or net bent as I know you understand. Therefore if my silicone is far to viscous less will be required in chamber 2 to achieve lock, thus locking at possibly an earlier temperature.


Jim

I'm now also concerned about what I'm going to receive from the dealer....one of the reasons I started to discuss here. But assuming that I still have my bms I can resolve both the leak AND the potential of HOT coolant by simply swapping.

But, if those 'copper' '00's you tested are not of different algaman to mine (and your pictures do look greater in 'orange' (but bear in mind mine is 12years old), this means that both Sachs and MB appear to have no control over supply of two completely different parts. And they know this should be tightly controlled as they have admitted to a problem (only documented in the E500).

I cannot understand why two companies, MB and Sachs DO NOT distinguish.

My questions for you:

1. How do you explain why MB hasn't rolled out the 01 part if it's a known issue on the R129 and W140 - assuming the 01 part has been modified to reduce coolant temperature.

2. Why didn't MB place the 01 part in all R129 119 engines post 974/975 engines?

Must dash...be back tonight :)

A ton of posts in this thread, and you still think that the 'gel' in your VFC may effect the cutin temperature. Hint: it doesn't!

Maybe you are pulling my leg. . got to be that??? :confused: Have you forgotten that yesterday you found that your bms is "different" than mine; remember "1577" and "1577A"? It has different material, etc. That's why it operates at 85C.

So carrying you argument a little further, if you test your bms ALONE in water, it won't bend at 85C because the it NEEDS the gel in vfc chambers to help it bend??? You think that sounds crazy but that's what you have just said.

The BMS HAS TO BEND enough to allow the gel to 'migrate' but, IF IT DOESN'T BEND, the VFC will NEVER lock not matter what you have in the chamber. And it has to bend a goodly amount for the vfc to start to function.

You said the ". . the bms will bend but not much". It will bend linearly with increasing temperature but the "NOT MUCH" has to be at least 0.060" (or so) to start to act as a vfc.

Now you've said that your bms IS different than my BMS since you said ". .I still have my bms (and) can resolve both the leak and . . hot coolant . . by simply swapping". But you couldn't do that if your bms was the same as mine. And what happened to the 'gel' argument? You said that "viscosity of the gel may effect lock temperature". So what is the viscosity of the gel in the new VFC??? I'm sure you see that you are going around in circles! :confused:

Again you must be pulling my leg??? Maybe you mean "copper" in color??? But it's not copper, but brass. Brass is brass; it doesn't FADE with time. It still has its characteristic color and can be 100 years old and will still look as it does today.

The reason your bms is a different color is that it IS made of different material otherwise it wouldn't lock at 85C! We are going around in circles.

I can't answer those questions! That's what I posted in #145 since I tested what was supposed to be a 82C bms "01". That was also tested on the car with no lock-up. I think that these VFCs are OUT-OF-CONTROL but why that is, I don't know.