Coolant light - PeachParts Mercedes-Benz Forum

davidmash · #1 12-20-2008, 01:45 AM

I have a 1995 E300D. We went looking at X-mass lights and the temp nudeged up to about 100C. I noticed the coolant level light (orange radiator) come on very very faint at about 95C and it got a bit brighter at 100C. When we headed home and the temp dropped back down to operating temp 85C the light went off. I looked at the manual and do not recall seeing anything about it being a temp warning as well as a level warning.

Could it be a bad sensor or did I miss something in the owners manual and this is normal?

Thanks

compu_85 · #2 12-20-2008, 01:52 AM

Is the level low? If not it might be a grounding problem: Bad grounds will make the temp gauge go up. I'm not sure if the coolant level sensor is normally open or normally closed, however.

-Jason

LUVMBDiesels · #3 12-20-2008, 03:23 AM

Check the coolant. That light is a level indicator.

connerm · #4 12-20-2008, 06:08 AM

My coolant level light has come on before, out of the blue, even though the level is correct. I bought a new sensor, but it hasn't come back on in a while so I haven't changed it out. My wiring harness has been replaced. Just one of those gremlins.

davidmash · #5 12-20-2008, 09:51 AM

No, the level is correct. I checked last night when we got home. I don't think the temp is incorrect. When we were driving the temp stayed at 85C which is the normal range. When were idling through the neighborhood, that is when the temp started to slowly increase. I am pretty sure I heard the two Aux fans kick in every now and then.

The thing with the light is that it did not come on full strength. It came on very very faint and as it got closer to 100C it got a little brighter but no where even near full strength (may 10%) of how bright it is on start up with the rest of the lights. It is like it was acting as a warning indicator that 'hey, your heat is starting to increase'.

Bio300TDTdriver · #6 12-20-2008, 10:45 AM

That would be a nice feature on the OM603 equipped cars. My light only comes on if the coolant level drops.

If it was my car I would be wondering why the temp was getting up to 100 this time of year. Did you have a warm front move in? Were you using the A/C?

Quote:

Originally Posted by davidmash

No, the level is correct. I checked last night when we got home. I don't think the temp is incorrect. When we were driving the temp stayed at 85C which is the normal range. When were idling through the neighborhood, that is when the temp started to slowly increase. I am pretty sure I heard the two Aux fans kick in every now and then.

The thing with the light is that it did not come on full strength. It came on very very faint and as it got closer to 100C it got a little brighter but no where even near full strength (may 10%) of how bright it is on start up with the rest of the lights. It is like it was acting as a warning indicator that 'hey, your heat is starting to increase'.

davidmash · #7 12-20-2008, 11:54 AM

I twas close to 60 out side but we were idling through a neighborhood behind other cars for about an hour or so. Once we picked up speed and the traffic thinned out the temp went back to normal and the light went out. The temp spike to 100C did not strike me as odd considering the circumstances. It never went above 100C (actually it stuck just below the 100C line).

Jeremy5848 · #8 12-20-2008, 12:43 PM

It sounds like your car is doing what Mercedes designed it to. When stressed, as yours was, the aux fans come on to increase airflow over the radiator. It is also possible that the viscous fan coupling in the mechanical fan is not working properly -- it should make the mechanical fan speed up when the coolant temp approaches 100C.

The coolant in the expansion tank gets warm but it will not be at the same temp as the coolant in the block since there isn't a lot of flow through the tank. Nonetheless, the heat may be affecting your coolant level switch in some novel way. I suspect that the problem will gradually worsen with time. Replacing the switch should eliminate this problem.

Jeremy

davidmash · #9 12-20-2008, 01:30 PM

Coolant switch being the coolant level sensor in the aux tank by the battery?

Bio300TDTdriver · #10 12-20-2008, 01:33 PM

Yes, the floating switch inside the tank. You may want to replace the tank as well. I'm not sure if the '95s came with a silica pack or not, but the new tanks have one to help protect the cooling system.