Coolant

[imadoofus]

My '94 E320 seems to be very slowly losing coolant. Every three weeks or so, I have to put 1.25 litres in it.

I don't have a head gasket problem. I don't have any visible leaks, and I have no idea where it's going.

The only other idea I have is that it's evaporating. I'm not sure that my electric fans are working and occasionally, the temperature gauge goes over the mark between 80 and red (100?) At this point, if it is boiling, then I guess the vapour is being returned to the expansion tank, and somehow exhausting through the overflow pipe. Or, it's exhausting somewhere else in the system.

Two questions (and then another one):

1) at what point should the aux fans kick in, and can I test them somehow (shorting the sensor circuit or something)?

2) Where the heck is my water going?

3) Where's the sensor that triggers the fans? I guess this might need replacing.

Thanks for your help.

PJ

 

[Captain Peacock]

My '94 E320 seems to be very slowly losing coolant. Every three weeks or so, I have to put 1.25 litres in it.

get a new radiator cap, see how that goes

 

[IanT]

When mine lost coolant I found that the radiator had failed along the seals at one end. Different construction to yours I'm sure, but it didn't drip out and was so well hidden it took some looking for - I only spotted it by chance at night as there was a slight wisp of steam across the headlights while parked up.

Ian.

 

[Vlad]

I had a E280 with the M104 engine as per your E320 and was loosing coolant. Checked all of the usual areas and found nothing wrong. Took it to my local indi and straight away he got a torch out and looked at the rear passenger side of the engine and sure enough the side of the block was wet.

Turns out that its a fairly common problem on the M104 engine and its all down to a small "O" ring that fails where a hose enters the block just below the lifting ring on the engine. The part costs nothing....the repair is all down to labour as its in an awkward spot.

Worth a look

 

[imadoofus]

Right then.

Thanks for the input everyone, I'll try these things (in increasing order of cost), and report back.

PJ

PS: Does anyone have any ideas about my electric fan questions above?