coolant level warning light staying on..

[mike]

Has anybody experience of the coolant level warning light staying on for 2 minutes or a mile or so after first cold start of the day then going off and not coming on again all day but on again at next days cold start..the coolant level seems ok and temp gauge is ok..?...its a 1997 C180 auto with no air con.

 

[Hellme]

I've had this sort of problem with my '91 180E. It didn't go off - it just stayed on all day. I knew there wasn't anything wrong because the coolant level was fine.

Turns out the connector was crusted with dried minerals from the coolant liquid. When the connector is not properly passing current from the meter inside the reservoir, it reports low fluid levels. In your case, I'm guessing that the connector is frosted with some mineral deposit, hence the cut out when you first start the car. As you drive and the heat builds up, the deposits lose the frost and connector passes current.

To fix it, I'd suggest pull out the connector from the reservoir tank, brush it off and make sure the socket it plugs into is clean of any debris or deposits. Reconnect and see what happens.

Hope this makes sense.

 

[paresh]

Hi Mike,

I agree with Hellme.

I had the same problem on my 1994 C180. I knew that there was enough coolant in the header tank on top of the radiator but still the low coolant light used to com eon intermittetly.

Traced the fault down to a faulty sender unit on the header tank. Minerals etc had collected at the electrical connection of the sender unit and it was this that was causing the false 'low coolant' reading. I removed the sender and cleaned the connections and retried. All was fine for a while and then it started happening again after a few months.

I then replaced the sender unit with a new one from the stealers and everything was fine. Apparently the sender unit acts as a seal and if the tolerance become too high, coolant can slowly seep out between the sides of the sender unit and header tank and lead to the mineral deposits.

Try cleaning the electricals connections and failing that fit a new sender unit. The unit is not too exbensive - about £10 + vat.


Hope this helps



Regards



Paresh

 

[mike]

Ok..guys i will investigate further along the lines you suggest and let you know what happens....thanks