W123 fan clutch? overheating

[Uber Huge]

1985 230 TE
This car runs at a steady 80C when driving.
However, when stationary, the temperature increases and can go up to 120C.
I don't think there's anything wrong with the thermostat, radiator, etc.
Can it be my fan is turning too slow when the engine is idling? I have counted it at 88 revolutions in one minute (the fact it's slow enough to count suggests to me it's too slow to cool the radiator).
Can anyone verify if this is normal please? I think it is too slow and therefore the fan clutch is not kicking in when the temperature climbs.

 

[grober]

If you have an electromagnetic clutch quite often its the thermal switch on the cylinder head that goes faulty. Test by shorting across the 2 pins - if the fan then runs you have your answer.

 

[219]

Is it not a viscous coupling on these cars ?

 

[Uber Huge]

Thanks for the reply, hm.. not sure what kind of clutch it is. I have read contradictory things about it.

So, next question, anyone know what kind of clutch it is on these or how I can tell?

But more importantly, does anyone have one of these and can tell me if the fan speed I've observed, 88rpm, is slower than it should be for a hot engine at idle. I'd like to eliminate this if possible.

 

[Uber Huge]

(Looking at buying a new replacement fan clutch suggests it is a viscous type - because that's what's available)
But before I go replacing anything, I'd like someone to verify that the fan IS too slow and therefore the fan clutch may need replacing...

 

[grober]

use search for the viscous coupling carrot test NOT K!

 

[Uber Huge]

Thanks, I think I've ascertained it is a completely ineffective fan clutch. I didn't know anything about fan clutches this morning...
The "carrot test".
Well, you can do what you like with this fan, even when the engine is very hot. I could even spin it back the other way, with the engine running!
Now the only way to know for sure is by replacing it

 

[Merckenzie]

First thing to try is the thermostatic switch. As previous reply, disconnect the two terminals, wire across with the engine off, but ignition on position 2. You should hear a loud click. Try moving the fan blade. If it is tight to move or solid. You have found that the switch is faulty. Cheap £10 ish from GSF.
Please do not turn on the engine to test.
It went on my W123 230E and my current W201 190E (twice).
Other know issues are,blowing the fuse. Same as the heated rear window. The fan assembly is not the first thing to try.
Go for the cheaper options first!
Hope you find it.

 

[Uber Huge]

Thanks, I will have to look for this switch tomorrow. So is it the case that it could just be this switch and that the clutch itself might be fine?
BTW I did the carrot test with the temp gauge at over 100C, and the fan was completely free.

 

[krimat2005]

that indicate faulty switch

 

[219]

A viscous coupling does not have a temperature switch .

 

[spanner]

It doesn't have a viscous coupling.

 

[219]

How do you know ?

My 190E - also with the M102 engine - had one , as did both my W123's (with M110 engines) .

The OP isn't certain what he has , so it could be either viscous or electromagnetic .

 

[Uber Huge]

Thanks guys, I will find out tomorrow if it has this switch or not...

 

[stwat]

How do you know ?

My 190E - also with the M102 engine - had one , as did both my W123's (with M110 engines) .

The OP isn't certain what he has , so it could be either viscous or electromagnetic .

Are you sure Derek? The only petrol 190 to have a viscous fan is the M103 2.6.
All others have an electromagnetic fan clutch.

 

[219]

Yes , my blue 190 had one - I know because I took the fan off when I changed the water pump .

Even the Haynes manual says that some cars have an electromagnetic clutch and others have a thermo-viscous coupling ( in the section on changing the water pump on 4 cylinder engines ) , I checked last night before posting .

Mine was an early 190 , with multiple drive belts , same set up as in the W123 .

 

[Uber Huge]

switch location

Is the switch no. 3 in this picture? The one which pulls apart. The cable goes down do a spring under the fan clutch.

 

[grober]

THE SWITCH IS NORMALLY FOUND IN POSITION 1 certainly on the 190. Its G in the diagram the 3 pin H sensor is an alternative for cars with air con.

 

[Uber Huge]

Looks like the switch is no.2 in my picture. I took the cap off this and shorted it to ground, with the key in position 2. There was a loud click as the thin plate (no.4) moves into contact with the hub (no.5).
I intend to go for a drive to warm up the engine, let it sit on idle and get hot, and then see if shorting this again will engage the fan and cool the engine back down to 80C.

 

[Uber Huge]

Yep, that worked perfectly! Cooled the engine down from 100 to 90 in about a minute. Just got to replace the switch.