W124 fan coupling

[Mercedes 190E]

Hi All

Reading another thread about replacing the water pump on a 300 W124, it reminds me....

My temp gauge never gets above 45 degrees. I noticed that the fan runs constantly-I never realised it was viscous coupled ! Am I right in thinking that it shouldnt be running when the engine is cold? Puzzling thing is that the heater is fine-very hot.
Does the viscous coupling need replacement do we think ? If so, can anyone advise how much it will cost and how do I do it ???

 

[television]

Hi All

Reading another thread about replacing the water pump on a 300 W124, it reminds me....

My temp gauge never gets above 45 degrees. I noticed that the fan runs constantly-I never realised it was viscous coupled ! Am I right in thinking that it shouldnt be running when the engine is cold? Puzzling thing is that the heater is fine-very hot.
Does the viscous coupling need replacement do we think ? If so, can anyone advise how much it will cost and how do I do it ???

The visco fan runs all of the time, but only at low speed. it is thermo coupled,, when the engine reaches 80C, you can hear the click as the visco coupling cuts in and speeds up..

Your engine never going over 45C does suggest a faulty thermostat,,and running like this will make it very thirsty

 

[wireman]

As per malcolm your engine thermostat is dead and stuck open. If you dont replace it your engine will wear out prematurly due to operating at a temperature well below its design limits. Engine oils dont work properly or last long at low temperature either giving the poor engine a double whammy.

Your heater will work much better as well in spite of its current hot enough state, the 124 heater is one of the best I've met, at -5C I can have the windows fully open and still be warm enough.

You dont need a fan in a UK winter ram air will suffice, so only bother to change the visco if it is indeed duff, do the carrot test.

The visco coupling has either a hydraulic medium or clutch inside its hub which will provide more torque to the fan as its hub gets hotter, usualy this is setup to become incremental at temperatures above 70-80-90 degrees.

To do the carrot test:- get it hot and try to stop the fan with a carrot instead of your hand, if the coupling is providing torque then the carrot will be chopped up, if it aint the fan will stop turning. Take care that your arm is not in a position wherby it can be dragged towards the fan or belt, carrots (uncooked) are tougher than skin and bone.

The coupling is bolted to the water pump shaft and special tooling (model and age dependant) may be required to lock/hold it while its unbolted.

 

[Mercedes 190E]

Thanks guys. I will get me to GSF for a new thermostat then ! Any particular difficulty in changing it ? (I have done them before but not on a Merc.)

 

[television]

Dead easy on yours,,its 32 in the link

http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=M&cat=505&SID=20&SGR=015&SGN=01

 

[Gazzaj]

I have just done it, be carefull not to split the thermostat housing, mine hadnt been shifted in 20 years, so when I re started the car today it split, its worth sticking a new one on for £8.00, get one of those too. The thermostat I got to needed the edges draw filing as the fit was very poor.

 

[Mercedes 190E]

Thanks guys. Was the thermo housing from Merc or GSF ?

 

[wireman]

You will also need the O ring gasket.

 

[Gazzaj]

The housing was from Eurocar parts in preston. It comes with the O ring for £8.00

 

[Mercedes 190E]

Thanks all.

 

[gandfmannahouse]

Have just bought a 1990 190E 2ltr auto. Thermostat housing leaking from fractures in the top plastic half. GFS will only supply a complete unit for £50 ish whereas the local Merc main dealer will supply a metal replacement for the top for approx£35. It pays to shop around, including Mercedes themselves, for spares.

 

[Mercedes 190E]

Hi Guys

Fitted a new thermostat to the 300 TE without problems-dropped straight in, didnt split the housing or shear any bolts-very pleased with myself really !
However, although the thermostat is now clearly opening when hot (By feeling the top hose) the gauge still only reads as high as 55 degrees-which is more than it used to, but is it enough? If not, where is the temp sender located as I think that is my next stop. (Unless anyone has any other ideas!)
Did the carrot test on the fan when hot and it cut the end off, but I forgot to try it when cold, when presumeably the fan should stop when it hits the carrot ?
Thanks in advance!

 

[television]

The visco fan never runs at full power when cold so no problem with the fan,, the air temp is very cold at this point in time, and will take much longer to get it up to running temperature

 

[Mercedes 190E]

I thought that too malcolm, but surely the temperature measured on the gauge is the internal engine temp rather than the ambient? i.e. would the thermostat be opening at 55 degrees?

 

[The Crooner]

John

Are you sure you believe the gauge?

The temperature sensor for my 230 cost £18 from the dealer IIRC.

My fan is electromagnetically controlled, and a new three prong sensor sorted out the fan, and gives me a believable temperature guage setting.

Trouble is you will again need to drain some coolant to fit it.

I'm now convinced that for control items - sensors, thermostats etc you should buy from Mercedes - they just seem to work better.

Cheers

Tony

 

[Mercedes 190E]

Hi Tony-I'm not sure I do believe the gauge, but Malcolm seems to think the reading is OK-I'm not sure because I dont really know these cars yet and Malcolm has vastly more experience than I have! My fan is a viscous coupled one so wouldnt be affected by the sender, but as you say, if there is any doubt the sender is working properly I will change it-once I have found it !!

 

[The Crooner]

Hello John

I just changed my thermostat - I was consistently well under 80 degrees before, now its a bit over 80. Its an 87 degree thermostat, that's when its fully open, so I expected a reading between 80 and 85ish, which is where I am.

Tony

 

[Mercedes 190E]

I think that mine is also an 87 degree thermostat, so if it is opening correctly (Which I am pretty sure it is) then logically my gauge should read along similar lines-does that sound right? Anyone know where the gauge sender is on a 300 TE ? (Had a look round, but can't see anything obvious on the cyl head or thermostat housing.)

 

[television]

Lets start again.

On the cars with the electric clutch, the senders, on top of head front right do play up and fail quite often, and stop the fan from running, or fail short circuit leaving the fan on all of the time.

Cars with a Visco fan have a bi metal strip built into the base of the fan, when the engine reaches 80c you can hear the bi metal strip click and the fan speeds up.

Water should not be flowing around the engine at temperatures below 87c as this is the range where they open, only when open, does the water flow fully.

Is the gauge reading correctly ?? the sender for the gauge has to sit on top of the head ( the hottest part in the water system) this can be found easily. When the engine is hot, turn engine off and just pull off one of the spade connectors, turn on the ignition, and the gauge will probably show max (could be the other way around and indicate zero) So then, this is the sender that Drives the gauge, and this gauge has nothing to do with the running of the engine.

A poor mans double check is to place a house type thermometer on top of the rad, as the temperature here is at the identical temperature as the top of the head, then compare the readings of the two.

Any reference that I made to ambient temperature before was the outside air temperature, not the engine or the car.

I ran my 1990 300TE when I lived in Sweden, and I could not get it hot enough. Engines work at their best at 105c, the engine fan coming on at 80c is to allow for thermal runaway, so it starts to cool the engine by drawing air through the rad, and it takes time for the water to cool down a little and have any effect on the temperature of the engine. At the same time the rad thermostat has opened giving the correct water flow through the system.

I blanked off the bottom half of my rad to make the car drivable in winter. If the engine is running at 50c max, then by the time the heater fan has moved the air though the matrix, it will be far too cold for comfort.

If the water is flowing through the rad at 50c then the thermostat must be faulty.

 

[Mercedes 190E]

Ok-thanks Malcolm, that makes things a lot clearer. I believe that the new thermostat is working fine (The old one definitely didnt) so it seems that the temp sender might be at fault. I will test it, but I really cannot find it! Tried the Russian site, but can't find it on their diagrams either. I have looked around the cyl head and housings etc but can't see any obvious switches.
Thanks.