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  #1  
Old 06-28-2002, 03:03 PM
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Exclamation M119 Viscous Fan mod & problems with aux. fan resistor-mod

Here's an interesting comment by Stu Ritter, current technical editor of the MBCCA's "The STAR" periodical, and former MB shop-owner (35+ years experience), on overheating M119's and modifying the viscous-fan cut-in, as well as possible problems with the resistor-trick, and a lower temp. thermostat.

JimF, Guido, comments?

:-) neil
1988 360TE AMG
1993 500E
===========
> Thanks Stu! I was just getting ready to install a *new* radiator
> (mine's original 10-years old), and replace the viscous fan with a SPAL
> puller-fan at 2780 CFM, on an adjustable thermostat as well.

The problem is the viscous coupling. I've done a lot of work here
to get my car to run cool. Now, with 95 degrees in Denver and full tilt
A/C running, I'm staying under 90C. Actually, it only goes up to 90 when
I'm idling for awhile at a stop. It stays at thermostat most of the time
now.
I was seeing 115-120 under these conditions. I found that the viscous
coupling wasn't working as it should. I went through three of them, and
guess what, they all worked the same way. I discussed this with the
chief
MBUSA engineer. He said that is the way they are supposed to work.
The fan clutch wouldn't engage until the strip saw 107C which really
meant
110C air going through which meant the radiator saw 115-120C. If you
listen carefully to the fan you will see how quickly it cuts out. It
only locks
on when you get up around 120-125C which is really bad. This little mod
takes care of the problem and counters the factories pathetic
engineering.

I took the viscous off the engine. You can carefully remove the
bimetallic
strip which has the pin attached. Drill a small hole (say 4mm) and
thread
it (say 4mm). Get a little 4mm bolt with two nuts. There isn't enough
thread on that thin strip to trust the threading. Screw the bolt in and
double
nut it, one on each side of the strip. Bow the bimetallic strip around
1mm.
This will give you full tilt fan engagement right up to the high speed
disconnect
around 3,200 rpm. You won't believe the amount of fan noise. It's noisy
but the engine runs cool as a cucumber. For winter, I reach down with a
4mm wrench, loosen the nuts, back out the bolt the 1mm and have a normal
(ha ha ha) viscous coupling during the winter when I don't need the fan
howling all the time.

> Also, the resistor trick
> (http://pages.prodigy.net/jforgione/MB_CTS.html) hasn't helped enough. I
> can really feel the "retard" and loss of power when the engine gets hot.

There are problems with the resistor trick that took me a long time to
figure out. Don't do it. That temp switch provides a temp signal to far
to
many things to trick it the way I did. It shouldn't be done. Once you
study
the wiring diagrams, you'll see what I mean.

> BTW- Satish had mentioned some 70-C thermostat, but I can't find one.

DON'T EVER, under any conditions use a thermostat that is rated lower
than
the factory spec. There is no quicker way to wear out an engine
than to run it cool. It is better to run it at 120C than at 70C. At 70C,
the
engine
still thinks it's in the final part of the warm up cycle. Wanna talk
about
wearing
something out. Excess fuel will wear it out so fast it will make your
head spin.

You will also be running the cat with too much fuel for too long. No
good.
Disastrous
idea.

Stu


Date: Fri, 28 Jun 2002 10:24:45 -0600
From: Stu Ritter
Subject: Re: [MB] Viscous fan fix for hot M119s (Was: 124 aux fans on
all thetime)

> Stu,
> As someone who has never removed a viscous fan clutch, how hard is it?
> Also, for switching back to "normal" operation in winter, do you have to
> remove the clutch?
>
> Steve Wengel

The manual says to remove the radiator. We have been able to sneak
it out without taking out the radiator. Just take off the shroud.

Switching back does not require removing it again. Don't put the 4mm
bolt at the center of the strip but rather out toward the end. Just
figure
that you have to lift it about 1mm to get full tilt fan action. I have
done
it twice now and it takes a minute or two on a cool engine. When I go
to set the 1mm clearance, I use a screwdriver and pry the strip up
and use the screw as a set screw, rather than trying to use the threads
to set the clearance. Works like a champ.

I just came back from the shop. I had to deliver something. It's about
88-90 in Denver right now and with A/C on, it was staying at thermostat
temp. One needle width above the 80C mark. Just right.

Doing research for my book, I found that the temp sensor that I had
jumpered provided a signal to the LH-SFI injection unit that determined
mixture. My car has been running better since I removed it. I didn't
think to go past my nose when researching the resistor affect on the
switch and changing the value seen. That signal is looked at by both
the LH control module and the EZL/AKR ignition module.

Stu

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  #2  
Old 07-01-2002, 11:24 AM
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You can still use the resistor mod on the 190e 2.3 engine which has a seperate fan switch to turn on the electromagnectic fan.

Good post STU!
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  #3  
Old 07-03-2002, 01:35 AM
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I did Stu's mod, and boy can you hear that fan roar. And it does a great job. Driving in 85F on a 70% humid day, and the car never got over one-needle width past 80C at 90MPH, and never over 90C when creeping through a 15-minute delay at 10-20 mph.

The only problem, it sucks down power; which means you have to give it more gas to get it moving the same way, and gas mileage suffers.

I think I'm going to really look into electric fan (s) with a thermostat. . .

:-) neil
1988 360TE AMG
1993 500E
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  #4  
Old 07-03-2002, 11:33 AM
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Everyone is entitled to their opinion even though it's not correct!

All MB autos that employ a separate CT sensor, B10/8 (M119 engine), use that sensor to control the A/C and Aux Fan(s).

Furthermore that sensor (B10/8) is not used to control the mixture, fuel mapping, etc. In short, it does not control any function that has to do with the engine or engine electronics!

Yes, it makes the A/C 'think' that it's a little warmer than it really is but no big deal.

The ECT sensor (B11/2) connects to LH-SFI module and is used to calculate air/fuel mixture and idle speed correction. Also the EZL/AKR module (N1/3) uses this info.

Stu's comments have nothing in common with my Cool Harness mod. He is mistaken!
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Last edited by JimF; 08-17-2002 at 01:20 AM.
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  #5  
Old 07-03-2002, 11:49 AM
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An added note to JFs reply..
Not only are there two seperate sensors, but the later models retained the same system but encased the two into one 4 pin connector sensor.
The single 4 prong still has two seperate thermistor circuits
[both with the same values] , but are isolated from one another electrically so as not to feed info from the aux fan one to the engine management FI/Ignition module....

If both were referenced for Eng management, then two sensor
circuits would be unneccessary...
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  #6  
Old 07-04-2002, 02:45 AM
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JimF, and Arthur Dalton-
Are you 100% sure about the resistor mod. Stu is the editor for the Star and a former shop owner I would think he knows what he is talking about.
I just dont want anything to go bad on my car because of the fan mod.

neil-
I am interested in this mod you did. Dont know if I will keep the resistor or not but I would like to try the 4mm bolt.
Can you explain it a bit better then in orignal post. If you had pics that would be great. Do the aux fans come on more? I am just kind of confused on driling a hole and haveing my fans work better.

Excuse my Ignorance.

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  #7  
Old 07-04-2002, 03:06 AM
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Neil holds the key!

Subman, et al:

It appears that Neil has caused this problem because of comparing apples and bananas! However Stu Ritter's comments are also incorrect. Since Neil hasn't posted a 'clarification' of his initial post, I guess I will.

As I stated in the original thread, when Donnie (Benzmac) made the same 'shoot-from-the-hip' comment (as did Ritter), it too was not correct! Here's the thread, besure to read it. How to change Aux Fan cut-in point

So bottom line, my web page (my menu #17) that explains the theory of operation and the MS thread above are correct. As stated, the B10/8 sensor controls the A/C and Aux fans and does not affect the fuel injection, mapping, etc..

You car is safe!!!

Maybe Neil will favor us with an answer! He has sent me an email trying to clarify what he has created but has not yet posted here.
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  #8  
Old 07-04-2002, 11:48 AM
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Ok, here's what I think happenned, including me cross-posting from the Ritter-Easley Mercedes list and the Mercedes-shop forum:

1) Stu had written about jumpering sensor B11/2 which provides engine coolant temperature to the LH (engine fuel-management system) system- Stu realized this is wrong and posted that this was wrong;

2) Jim's research revealed that jumpering (with the correct value range resistor) sensor B10/8 which DOES NOT feed info to the LH system, only the air conditioning system, will fool the aux. fans to come on early;

3) In Stu's post about not doing it, there was no mention to the sensor he was referring to, so I incorrectly assumed it was B10/8; this caused the confusion.

In short, don't jumper B11/2, but do jumper B10/8.

Here are schematics for the W124 with M119 engine and LH; and the W124 M119 Air Conditioning system:
http://www.silcom.com/~neilv/sportline/images/W124-ACC-M119-LH-83-6.pdf
http://www.silcom.com/~neilv/sportline/images/W124-LH-M119.pdf

Regarding modifying the engagement point of the viscous fan (the thread that started it all!):

1) Stu is correct, the bi-metallic strip in front of the viscous coupler will not engage until heated until 107C. Unfortunatlely that means ambient air temperature will need to get to 110C, with a radiator temp. off 115-120C- NOT GOOD.

2) The bi-metallic strip is held in front of the viscous coupler with just four small tabs that can be bent OR, just gently bend the bi-metallic strip to remove it;

3) Once removed, you'll notice a pin that goes between the viscous coupler and the bi-metallic strip. The bi-metallic strip pops up and out towards the radiator about 1-2mm allowing the pin to move up. This engages the fan until about 3500-3800 RPM when it automatically disengages;

4) The mod, should you accept it, is to drill one 3.5mm hole into the bimetallic strip, and insert a 4mm bolt, such that the bi-metallic strip is popped up about 1-2mm; I did what Stu did and used a 4mm bolt and two 4mm nuts, plus I tapped the 3.5mm hole with a 4mm tap. I tapped the hole in the strip about 5mm out towards the end of the strip from where the pin and strip meet, or 10mm from center;

5) There is no doubt about it, this MOD works, however it does eat about 10-15 HP, and you fan is always on until the cutoff RPM.

6) Driving at night with 57F femps, the car gets to 82-84C, so the thermostat is open and I sill can get heat- in the day never past 90C in town, 85C on the freeway.

7) Don't try this unless you remove the radiator OR have access to special tools. I use a OM603 fan clutch holder tool, and the 8mm/10mm A/C clutch tools to remove the viscous fan without removing the radiator. You can find them here: http://www.technictool.com/

Hope this ends all of the confusion.

:-) neil
1988 360TE AMG
1993 500E

Last edited by ke6dcj; 07-04-2002 at 08:35 PM.
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  #9  
Old 07-04-2002, 12:04 PM
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cooling cont

I am with Jim F. This set up has worked. Im not changing anything. Lets just be thankful,we live in southern calif and not
texas or AZ, with ambient temps scorching our cars would not be happy campers. I think Mercedes should of put in bigger radiator, since this engine is just rammed in that small compartment. I have a service bulletin from MBAG/stating our cars can run up to 110 C. and before red zone long as all system are operating normal.waterpump,fans etc. I'm going to find this bulletin from yrs ago,and post it on here.

My temp gets up to about 90-92 then fan kicks on and stays on for about 30-45 seconds then goes off.


thats all i have to say.
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  #10  
Old 07-04-2002, 02:08 PM
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Tnx for the clarification!

I believe that you have it correct. Stu tried to use a resistor across the B11/2 sensor, which is a no-no! That would explain his comment, ". . . loss of power when the engine gets hot".

Your schematics are very clear and easy to read. Tnx!
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  #11  
Old 07-05-2002, 03:39 AM
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Not sure how Jims mod affects this, but........

The worst thing for an engine is heat cycling...i.e. getting hot, then overcooled, then hot again. On the Elise there is a bit of a design flaw in that the thermostat is next to the engine, but the radiator is 8ft away in the fron tof the car. This water gets supercold. The moment the thermostat opens, cold water rushes into the engine. The Thermostat then closes quickly, and the water heats up. This repeats, and eventually the head gasket will go (or the head will warp).

My point is... it's better to have a car run at 110degC all day long rather than oscillate between 85 and 105degC.

Bri
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  #12  
Old 07-07-2002, 11:29 AM
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Not certain about that???

Since Mercedes states that an engine meets specs at 80C, then certainly operation between, say 85C to 95C would be ok.

In fact most MBs do just that! Without A/C here in southern CA, my car runs between those limits. So I cannot believe that any damage will be done. My engine has 101K miles on it and is still running strong.

However, I do believe that running the car 110C all day long could cause some bad results. One that I can think of a severe retardation of timing at the temperature.

I do agree that cycling between 85C and 110C would be not the ideal operating conditions.

Interesting story: saw a '91 380SEL where the engine 'melted'!! The woman that owns the car let her 19 yr old son drive it and it overheated. The temp gauge was on-the-pin and he didn't notice anything wrong so he continued to drive it.

The car got so hot that the radiator MELTED! The plastic endcaps were deformed badly. The top 'plastic' pieces on the engine melted like glue! The engine froze 'solid' but, I was told, there was no smell of anything burning. That's hard to believe.

Engine was replaced along with the radiator and a number of other components. It runs great now!
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  #13  
Old 07-12-2002, 07:40 PM
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I don't know much abt this but I had a 90' mbz 300e and it overheated once and I didn't notice it too, the car suddenly stopped and smoke came out of the engine bay, I towed it to a mechanic and he said that my block had cracked...I didn't know why.. but this was a few years ago...
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  #14  
Old 07-14-2002, 12:23 PM
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I have done a little research into the electric fan upgrade. Say a pair of narrow puller fans mounted on the inside of the radiator, which should be able to move 1500-2000 CFM of air each.

A pair of 14 inch fans should do the trick, but will the alternator be able to cope with another 20 amp draw? What is the alternator rated for? Will I need to upgrade to a different alternator?

The fan upgrade should be a sub $500 conversion, and would probably give a few extra HP, as a not too inconvenient consequence.

Any thoughts?
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  #15  
Old 07-14-2002, 03:39 PM
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Huge alternator-no problem as long as it's not the original (actually, mine IS the original & runs my nearly 100 amp sound system) which could be compromised.

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