Overheating E Class

[Ade - I'm back]

I have a 1991 230TE Auto which is prone to start overheating. Up till recently I have managed to avoid 'blow outs' but unfortunately on Christmas Eve she went like Moby Dick! I've been a real lazy sod and have done nothing about it but now is the time to get off my a*se and sort it. I have two prongs to my assualt on the problem - 1) Thermostat and 2) fan. Thermostat easy bit. Test and replace. Fan - not so easy. can anyone tell me where the fan switch is located? Also if this works how does anybody have any suggestions for testing the Electromagnetic coupling?

 

[television]

Are you sure the car is over heating, what is the temp ? or has the head gasket gone ?, the effect is the same except that your water system is being blown up.

Malcolm

 

[Ade - I'm back]

Mqalcom

It is definitely overheating. Red lining on temp gauge. Need to check fan op. hence query on how to test. Can't ever recall it cutting in.

Ade

 

[Bolide]

Overheating

If the car's overheating & losing water you've probably either got a leaky radiator or a blown cylinder head gasket. From your description I'd say it was the latter

Fill it up with water and run it at idle with the header tank cap off and the heater on. Leave it a few minutes to get all the air out of the system and top it right up

Then rev the engine to about 2500 rpm and watch what happens. The water level will rise a little but if you get bubbles coming up through the water or if it blows all the water out of the header tank your cylinder head gasket has gone

If this is the case and it's been overheating consistently you'll need to have the head skimmed to make sure it's flat

Radiator leaks can be difficult to find. Sometimes they leak after turning off the engine when the internal pressure rises. You'll need a clean, dry rad to see the leak

My money's on the head gasket, unfortunately


Nick Froome
www.w124.co.uk

 

[e36bob]

Overheating 124

If you believe it is the head gasket, try and borrow a pressure test kit.
My own 230 revealed a radiator with many a pin hole .
It also showed a failure in a rubber hose.
Good luck
Bob

 

[Ade - I'm back]

Thanks for the help guys. I will elaborate. The car has been running normally but when I stay stationary the car begins to heat up until I move again and it will then cool down to normal running temperatures . Unfortunately the other day I was stationary for too long, hence the 'blow'. The fan or thermostat had failed to operate. I am trying to ascertain how I test the fan as I suspect this is the cause. I have never heard it cut in. I know there is a fan switch but my Haynes ('only really any good for resting my tea cup on') manual doesn't say where it is. I think this switch is my first port of call before looking at the electromagnetic clutch.

 

[turnipsock]

If the temp stays stable when moving then there is nothing wrong with the thermostat.

The car will heat up when stationary as there is no air (well not as much) flowing through the radiator to cool it down. That's where the fan should kick in and blow some air through...it looks like the fan is the problem.

You could try turning on the heating full blast and see if this has an effect when you are stationary.

 

[Ade - I'm back]

Turnipsock

In answer to your query, yes with heating on full blast it does just about keep engine cool enough not to overheat when stationary (having spent many a wasted hour in traffic jams on the M25).Unfortunately forgot about this trick when delivering Christmas presents! Kinda crept up on me.

Since my last post I have tested the thermostat and it is ok. I would like to test fan switch but am unsure where the ****** thing is! Anyone know? Also if that proves ok, is the electromagnetic coupling servicable?

Just to aggreviate matters I crushed the Top hose radiator coupling on the radiator and now have to get a new radiator. Oh well c'est la vie! My problem is which one to get - Eurocar Parts list aircon and non air con versions. Although I have air con it is the retrofitted Mercedes Approved kit with a seperate a/c condensing radiator sitting in front of the main radiator. Will ordering the non air con rad make any difference. I assume an air con version has the condenser matrix integral with the main water matrix. Anyone out there know?

These and many other questions will be answered in next week's episode of 'SOAP'. - Sorry, couldn't resist it!

Ade

 

[turnipsock]

I haven't tried testing the fan but it looks fairly straight forward.

There are a couple of sensors near the thermostat. One should be for the clutch.

According to haynes it should have feed wire, black and red.

The other wire should be black or black/red/white.

If you short these two wires together, the fan should kick in.


A better test might be to check there is 12V on one wire and 0V on the other. As the temp rises 0V wire, should jump to 12V and the fan should kick in. This is assuming you can get a meter on the wires while the whole thing is connected up.


I'll go and have a look at mine.

 

[television]

this is a 102 engine, the switch for the fan 1 is on top of the head in the sensor box. If the one nearest front has 2 pins, that is for the fan coupling, if it has 3 pins, that is the same but has contacts for aux fan 2, marked red for climate / air
Fan 1 cuts in at 100c, aux fan 2 cuts in 110c
The connector on the fan is in line with the engine damper, one wire has always 12volt live.

Malcolm

Re Turnipsock, The fan has always 12v live, this will appear on both terminals when the fan is not working, when the switch cuts in it grounds one lead and circuit complete

 

[turnipsock]

The fan has always 12v live, this will appear on both terminals when the fan is not working, when the switch cuts in it grounds one lead and circuit complete

I thought it was 12V-fuse-switch-fan-ground.

Is it the switch indicated?

(The things I do for this forum, it's freezing out there)

 

[television]

I thought it was 12V-fuse-switch-fan-ground.

Is it the switch indicated?

(The things I do for this forum, it's freezing out there)

It looks like it to me,
The 12volt comes from fuse and goes to fan,one terminal, the other returns to the switch that grounds it and circuit complete.

excuse me young man putting it here, Yours really is a 102, I will remember that for the next time

Malcolm

 

[Ade - I'm back]

Thanks guys, at least I have an idea where the switch is. I half suspected it was by the thermostat housing. I will have a play later today and let you know how it goes.

 

[Ade - I'm back]

UPDATE - Shorted fan terminals on sensor and electromagnetic clutch operated with no worries. Deduce switch Bllxd, new one on order.