w124 e220 viscous fan question

[mr_day]

Hi, first ever post here, been trawling threads diligently for a year since buying an S124 '96 e220 (so M111 motor) wagon here in Germany where I now seem to live. 250kms on the clock (after my 10), runs beautifully at speed but has the dreaded idle shake n stall problem and have been slowly trying to eliminate that from cheapest solution (new sparks, air filter, OVP relay, new temp sensors last week) through to bigger jobs – unfortunately I think at this point it can only be the throttle body or something faulty in the..... wiring loom There's a mob here who do a reco on both those items fairly reasonably if you remove and send yours to them so that's next port of call. (someone suggested it could also be the fuel injection pump?)

Anyway, my actual question for now is that since replacing both temp sensors last week (the one that talks to the engine and the one that sends info to the dash) I've noticed that:


a) possibly the viscous fan wasn't ever coming on properly until now (ie. switching on high as opposed to just spinning freely), because you can definitely hear when that thing engages, usually after driving for 15/20 minutes in town – ie. perhaps the old temp sensor was indeed kaputt...

b) the temperature remains a lot more steady around the 85 mark (last summer it would float up to 100 odd and then something would kick in but I wonder if it was the viscous fan? Possibly aux fan? We don't run the aircon though, or at least keep it in E mode)

c) and here the problem: though the fan engaging is a good thing, after kicking in, it doesn't turn off – even when cruising down German country roads on crisp spring days when it definitely shouldn't require the fan to remain at 80-85.


Any ideas out there? Relay switching it on but not off? Faulty temperature sensor, though I think the it's precisely the new one working and triggering the fan to come on in the first place... damaged wire when I replaced the sensors?

Unlikely paranoid theory: could over-torquing the new sensor have damaged it? (I had to do that one by feel...)


Questions questions. Answers much appreciated. Sorry to start a new thread but haven't been able to locate this exact problem anywhere on the boards.


Ps. For what it's worth I've done the carrot test on startup to determine that the fan is spinning freely and "stoppable", though I haven't tried it when shutting down after reaching my destination. I'm not sure quite what that would tell me anyway.

 

[mattkh]

...........since replacing temp sensor last week (the one that sends info to the dash)
Please help increase my knowledge of this engine. Where on the engine is this sensor fitted..? Thanks
.......Unlikely paranoid theory: could over-torquing the new sensor have damaged it?
If this sensor had an O ring, then you would have had a coolant leak when over-torquing.

 

[mr_day]

...........since replacing temp sensor last week (the one that sends info to the dash)
Please help increase my knowledge of this engine. Where on the engine is this sensor fitted..? Thanks
.......Unlikely paranoid theory: could over-torquing the new sensor have damaged it?
If this sensor had an O ring, then you would have had a coolant leak when over-torquing.

Thanks for your response. Sensors in this one are at the front of the engine under the plastic cover.

Ok yep checked for leaks, all good.

 

[LostKiwi]

a) possibly the viscous fan wasn't ever coming on properly until now (ie. switching on high as opposed to just spinning freely), because you can definitely hear when that thing engages, usually after driving for 15/20 minutes in town – ie. perhaps the old temp sensor was indeed kaputt.

Temperature sensors will have nothing to do with the viscous fan. The two are independent. The fan senses when to turn on through physical means (usually a bimetallic strip that operates as a clutch or through a liquid that thickens with higher temperature as in Toyotas).
You could have no electrical system at all and a viscous fan would still work as normal.
If the fan wasn't engaging previously something else has changed to make the engine run warmer or the fan viscous unit has failed.
Try the carrot test when cold.
Start the engine and allow to idle. Put a carrot into the blades. The fan should stop with some resistance. If it cuts the carrot the fan coupling has seized.

 

[mr_day]

Temperature sensors will have nothing to do with the viscous fan. The two are independent. The fan senses when to turn on through physical means (usually a bimetallic strip that operates as a clutch or through a liquid that thickens with higher temperature as in Toyotas).
You could have no electrical system at all and a viscous fan would still work as normal.
If the fan wasn't engaging previously something else has changed to make the engine run warmer or the fan viscous unit has failed.
Try the carrot test when cold.
Start the engine and allow to idle. Put a carrot into the blades. The fan should stop with some resistance. If it cuts the carrot the fan coupling has seized.

Ok excellent info, thanks. Have done the carrot test cold, fan stopped no worries. It's more a case of once properly on, why it doesn't turn off when cruising, especially as it's still only 6 or 7 degrees outside at the moment.

 

[LostKiwi]

Ok excellent info, thanks. Have done the carrot test cold, fan stopped no worries. It's more a case of once properly on, why it doesn't turn off when cruising, especially as it's still only 6 or 7 degrees outside at the moment.

It gets heat from the engine to determine if it needs to be engaged or not.
The water pump spindle for example plus the ambient temperature of the air after its come through the radiator.
These both heat the viscous coupling and determine when it cuts in or out.
It's possible the bimetallic strip is bad but that requires a new coupling to change.
A viscous fan will always windmill and turn through drag on the coupling. Just because it turns doesn't mean it's shifting air. Again you can (carefully!) do the carrot test after a run by leaving engine running and seeing if the fan cuts the carrot. If it always cuts the carrot either your engine temp is high or your fan is coming on too low.

 

[mr_day]

It gets heat from the engine to determine if it needs to be engaged or not.
The water pump spindle for example plus the ambient temperature of the air after its come through the radiator.
These both heat the viscous coupling and determine when it cuts in or out.
It's possible the bimetallic strip is bad but that requires a new coupling to change.
A viscous fan will always windmill and turn through drag on the coupling. Just because it turns doesn't mean it's shifting air. Again you can (carefully!) do the carrot test after a run by leaving engine running and seeing if the fan cuts the carrot. If it always cuts the carrot either your engine temp is high or your fan is coming on too low.

Ok many thanks, will pack a carrot on the next run.

 

[Blobcat]

It gets heat from the engine to determine if it needs to be engaged or not.
The water pump spindle for example plus the ambient temperature of the air after its come through the radiator.
These both heat the viscous coupling and determine when it cuts in or out.
It's possible the bimetallic strip is bad but that requires a new coupling to change.
A viscous fan will always windmill and turn through drag on the coupling. Just because it turns doesn't mean it's shifting air. Again you can (carefully!) do the carrot test after a run by leaving engine running and seeing if the fan cuts the carrot. If it always cuts the carrot either your engine temp is high or your fan is coming on too low.

Packed up on my 110, just windmilling away but not shifting air - cab heater on full heat and blower on full got me home without it boiling over (again...)
Replaced the viscous coupling and all good again

 

[mr_day]

It gets heat from the engine to determine if it needs to be engaged or not.
The water pump spindle for example plus the ambient temperature of the air after its come through the radiator.
These both heat the viscous coupling and determine when it cuts in or out.
It's possible the bimetallic strip is bad but that requires a new coupling to change.
A viscous fan will always windmill and turn through drag on the coupling. Just because it turns doesn't mean it's shifting air. Again you can (carefully!) do the carrot test after a run by leaving engine running and seeing if the fan cuts the carrot. If it always cuts the carrot either your engine temp is high or your fan is coming on too low.

Ok so applied a carrot after the run and it stopped the fan, BUT... am I even taking about the correct fan? I was always checking the big fan between the radiator and the engine – that is the viscous fan, right?

Turns out the fan I was hearing coming on and never turning off was always the fan in FRONT of the radiator – the little one. This is the aux fan, right? And thus controlled by the electrics and so possibly affected by the new temperature sensor?

It always comes on after about 20 minutes, even if the whole trip has been cruising on country roads – so plenty of air naturally flowing through, and again, only 7 degrees celsius outside today.

 

[LostKiwi]

Turns out the fan I was hearing coming on and never turning off was always the fan in FRONT of the radiator – the little one. This is the aux fan, right?

That's an electric fan. If it runs at high speed all the time it's probably low A/C pressure.

Given you don't run the A/C (why do people do this???) The seals in the compressor have probably dried out and lost some gas.

 

[mr_day]

That's an electric fan. If it runs at high speed all the time it's probably low A/C pressure.

Given you don't run the A/C (why do people do this???) The seals in the compressor have probably dried out and lost some gas.

It's not that I don't run it, I just have it on EC – which I gather is the same thing... the three button system in these models is famously baffling. But yeah I do this because a) I've never liked aircon, b) it never blew very cold anyway, and c) it never gets that hot here... not by Oz standards anyway. Prefer the window down.

So that fan is not to draw air into the radiator then? Still odd that this cropped up only after the temp sensor replacements.

 

[LostKiwi]

The electric fan operates for two reasons:
1. To cool the air conditioning condenser.
2. If the engine temperature exceeds a given threshold it will assist engine cooling.

If the fan won't turn off it can be a symptom of low gas pressure.

 

[mr_day]

The electric fan operates for two reasons:
1. To cool the air conditioning condenser.
2. If the engine temperature exceeds a given threshold it will assist engine cooling.

If the fan won't turn off it can be a symptom of low gas pressure.

OK thanks, then it must be A/C related because the engine is steady at just over 80 degrees and like I said, running at 80-100kph down country roads.

 

[mr_day]

So the other day after a run I opened the bonnet whilst still idling to pull the temperature sensor wire, to see if that changed anything with regards to the AUX fan. However before I got to it the aux fan stopped of its own accord, leading me to believe that perhaps the heat dissipating with the open bonnet caused the fan to cut out. The engine temperature is certainly more steady around town and in traffic with the aux fan running, but it is ALWAYS running after the engine gets up to temperature.

So I'm still unclear why the fan would not also cut out when cruising outside of town in relatively cool temperatures.

Could this be a relay issue? Or is the engine really running so warm that even with a lot of natural air intake the aux fan is still required?

 

[Botus]

does it have functioning Air Con ?

many cars have an electrical fan to pull air through the AC condenser (the bit that sits in front of the engine cooling rad - and looks very similar), being an old car the AC will have an electro magnetic clutch and cut in and out based on its need / temp set point. The electric fan usually does the same

if an old car the engine cooling thermostat can wear out and get lazy (opening later than it should) and make the car run hotter than it should

 

[mr_day]

does it have functioning Air Con ?

many cars have an electrical fan to pull air through the AC condenser (the bit that sits in front of the engine cooling rad - and looks very similar), being an old car the AC will have an electro magnetic clutch and cut in and out based on its need / temp set point. The electric fan usually does the same

if an old car the engine cooling thermostat can wear out and get lazy (opening later than it should) and make the car run hotter than it should

It does have A/C but as I was telling LostKiwi I never use it... I remember it did blow a bit colder the time I tried it though.

I also don't think the car is running hot – if anything, since I replaced the temp sensors it is running bang on 83 or so, and stable, probably because this aux fan is coming on. My problem is why isn't turning off when it should... It could be an A/C issue but the "problem" only started when I replaced the temp sensors.

 

[Botus]

AC should be left on.... a domestic fridge works as its used regularly, car ones die because misguided people think its expensive... but opening a window or a sunroof (aside from making you deaf and wasps going in your face / up your sleeve) creates so much drag its almost as bad for the planet and fuel consumption. About 2% less with a window. But AC gets you safety benefits, cooler calmer and thus better reactions…. plus demisted windows and a lack of damp soggy electrics and rotting carpets inside the car

Thermostat was last replaced when ? and the new sensors used - genuine and the correct part numbers ?

 

[mr_day]

AC should be left on.... a domestic fridge works as its used regularly, car ones die because misguided people think its expensive... but opening a window or a sunroof (aside from making you deaf and wasps going in your face / up your sleeve) creates so much drag its almost as bad for the planet and fuel consumption. About 2% less with a window. But AC gets you safety benefits, cooler calmer and thus better reactions…. plus demisted windows and a lack of damp soggy electrics and rotting carpets inside the car

Thermostat was last replaced when ? and the new sensors used - genuine and the correct part numbers ?

Yes well thankfully not driving around in monstrous heat (I left that country) and for enjoyment/family/sanity's rather than economy's sake I reserve the right to open a sunroof or a window. There's no insects left anyway, right?

Car history is a bit patchy but will look into thermostat – it's a good reminder actually: what's the easiest way to obtain the genuine part numbers? Obviously putting W124 M111 OEM thermostat into google just results in miles of aftermarket ads, and some original parts are not Mercedes per se, but Bosch etc...

 

[Botus]

try this (it was the only 220 model I saw...)

M 111.960 - ENGINE COOLING SYSTEM > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Car. Engine - Power Systems ENGINE COOLING SYSTEM.

nemigaparts.com

FG 124.022 - RADIATOR > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Car. RADIATOR.

nemigaparts.com

don't use my info _ I'm not sure what engine / spec it is

THERMOSTAT 87 DEGREES;RANGE OF DELIVERY

001

A 11 120 009 15

-

$38.36

 

[mr_day]

try this (it was the only 220 model I saw...)

M 111.960 - ENGINE COOLING SYSTEM > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Car. Engine - Power Systems ENGINE COOLING SYSTEM.

nemigaparts.com

FG 124.022 - RADIATOR > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Car. RADIATOR.

nemigaparts.com

don't use my info _ I'm not sure what engine / spec it is

THERMOSTAT 87 DEGREES;RANGE OF DELIVERY

001

A 11 120 009 15

-

$38.36

Ok, many thanks. Will check it out.