W124 Electro-Magnetic (Clutch) Engine Fan

[NormanB]

Hi

I had a bank holiday motoring experience today and I feel a 'reet chump'!

Basically spent an hour in start stop conditions and engine temp rose...and rose until (I suspect) the expansion chamber pressure cap lifted and let go of the coolant - it was quite impressive. Fortunately I managed to slide over into a vacant parking slot within 10 metres!

Opened the bonnet and satisfied that it was not on fire (had a 'FUD' moment (fear uncertaininty and doubt)) and that there was only oil in the sump, fed the meter and took my daughter to the planned trip to the cinema to see Harry Potter, which fortunately was only a ten minute walk.

On return, the engine was nice and cool, rechecked the sump and relieved to find only oil and at a normal level. Topped system up with oggin and ran engine which soon reached normal operating temperature and thermostat opened at spec. No leaks found.

My guess is that the electromagnetic fan failed to cut in. What are my options where is the sensor - how can I test the unit electrically and is there a strip out option on the fan clutch or is it upkeep by exchange.

Grateful for any techie advice, wise words or guidance.

NormanB

PS: I fell asleep within the first 10 minutes of Harry Potter, my ten year old daughter is well trained and left me alone until I started snoring!!
She tells me it was a really good film!!

 

[Mikesmerc]

Hi Norman
same thing happened to my 88 230e a few years ago. It was the little brass sender unit mounted on the cylinder head at the front. Think there is a few units around there but the one you are looking for has a two pin connector :roll: . The way I tested it was by crossing the two terminals when the engne is running and the fan should cut in. Basically the unit packed in and wasnt completind the circuit when a specific temp was reached.
Cheap as chips fix.
Sorry if Im a bit vague but it was a few years ago and am working from memory. No doubt someone will correct me.
Hope this is of some help
Regards
Mike

 

[sunil sood]

had a similar problem on my 190e(1993)-the needle would climb all the way to the top in slow moving traffic.

it turned out to be a faulty fan switch-availbale from gsfcarts or eurocarparts as well. cost was about £10-easy job to replace with the right tools-my switch was a 3 pin and yours may well be a 2pin one.

the location is on the front right hand side of the engine with the bonnet open.

also if you do a search in the archives by preesing search and entering overheating or fan switch-you will get your answer there

 

[brasil]

mercedes engineering

Hi Norman
same thing happened to my 88 230e a few years ago. It was the little brass sender unit mounted on the cylinder head at the front. Think there is a few units around there but the one you are looking for has a two pin connector :roll: . The way I tested it was by crossing the two terminals when the engne is running and the fan should cut in. Basically the unit packed in and wasnt completind the circuit when a specific temp was reached.
Cheap as chips fix.
Sorry if Im a bit vague but it was a few years ago and am working from memory. No doubt someone will correct me.
Hope this is of some help
Regards
Mike

hi norman,

sorry to hear about your mishap,however GREAT CARS when they are "running fine"

 

[brasil]

mercedes engineering

Hi Norman
same thing happened to my 88 230e a few years ago. It was the little brass sender unit mounted on the cylinder head at the front. Think there is a few units around there but the one you are looking for has a two pin connector :roll: . The way I tested it was by crossing the two terminals when the engne is running and the fan should cut in. Basically the unit packed in and wasnt completind the circuit when a specific temp was reached.
Cheap as chips fix.
Sorry if Im a bit vague but it was a few years ago and am working from memory. No doubt someone will correct me.
Hope this is of some help
Regards
Mike

hi norman,

sorry to hear about your mishap,however GREAT CARS when they are "running fine"

 

[GaryC]

hello,

I have the simular problem few year ago, with my W124 300E, in a sunny, exteremely hot day, travelling in the start stop condition in a jamed motorway for an hour, I found that the engine goes very hot, I also suspect that is the viscous couple of my fan got problem, so I shift to 'N' then step on the engine to test the fan, and I can clearly heard the noise that the fan couple work fine, and it could cool down immidately!

Ths problem is, when in extereme condition, the engine speed is not fast enough to cool down the coolant. So what I have done, is to install an additional cooling fan in front of the radiator, with a little coolant temperature sensor, to switch it on when it have to, then the car never have any cooling problem.

Gary!

 

[NormanB]

Hi Norman
same thing happened to my 88 230e a few years ago. It was the little brass sender unit mounted on the cylinder head at the front. Think there is a few units around there but the one you are looking for has a two pin connector :roll: . The way I tested it was by crossing the two terminals when the engne is running and the fan should cut in. Basically the unit packed in and wasnt completind the circuit when a specific temp was reached.
Cheap as chips fix.
Sorry if Im a bit vague but it was a few years ago and am working from memory. No doubt someone will correct me.
Hope this is of some help
Regards
Mike

Mike you were right on the money - thanks.

Just to let you know and for those that may follow.

The thermo-switch had failed. This is the brass coloured 'jobby' at the front of the head beside the thermostat. A 22mm deep socket is required to remove and replace. The electrical connector is rectangular in shape and there are 2 pins on top of the thermo-switch. The original had an aluminium sealing washer, the replacement came with a copper one.

The dealer had them in stock but there are different part numbers so you need to provide chassis number - cost £16.

You can test if the electro magnetic clutch is functional by bridging the two connections of the rectangular plug with the ignition on - you should hear a 'clunk' and you will be unable to turn the fan by hand - unlike the condition without the bridge or ignition off when it should freewheel.

Time to replace - max 10 minutes including supping a mug of tea!

To be honest I reckon this had been duff for yonks I just had not experienced such a lengthy period of stop/start traffic before.

For those with a electro magnetic clutch on their engine fan I most heartily recommend that you carry out the test described above - particularly as summer is supposed to be happening some time soon.