Mysterious 95 E320 radiator light/Brown gunk in coolant reservoir
 

My 95 E320 wagon's rediator light is barely on? I can only see it at night? I have topped off the wiper fluid and coolant fluid (thats too full now) When I TOPPED OFF THE COOLANT FLUID THERE WAS THIS BROWN GUNK ON THE TOP OF THE GREEN COOLANT LIKE OIL!!!!

Sensor May Be Bad
 

I think there is a sensor, screwed into the radiator itself, to determine the level of coolant in it. Sounds like that sensor could be bad. I'd disconnect the sensor and see what the light does. Of course you don't want to remove the sensor with coolant in the radiator and do this when engine and radiator are cool.

The brown gunk and the radiator light are two issues.

I would flush the fluid and recheck later to see the condition of the coolant.

The "dim" radiator indicator is a sure sign of a failing sensor. Corrosion eventually does this in.

You can clean the contacts for a temporary cure, but it will just come back weeks or days later.

Replace with a new one. Easy 5-minute deal. Good time to do it is during a flush and refill...or in my case, when the heater hose burst and I lost all coolant anyway! :eek:

Oh, oh,................headgasket ? :eek:

The coolant level sensor is in the expansion tank. Brown gunk in the expansion tank is a symptom of a bad head gasket. Confirm that's the problem and get it fixed sooner rather than later.

It's the sensor wires and plug
 

On the expansion tank. I had the same issue when it rained out - my radiator low fluid lamp would start to come on dimly. I pulled the plug connection off the sensor and the spades had a good bit of greenish crud/corrosion on them. I cleaned it all off and reassembled with some di-electric grease to seal it and it has been fine for a year or so.

Can't help with the brown funk - hope it's not a head gasket.

Rgds,
Chris W.
'95 E300D

The sensor itself may also be affected by the goobis in the expansion tank. My '95 had the same symptom, by removing the sensor and cleaning both the electrical terminals (as stated before), and the hinge that moves (depending on the amount of coolant in the tank) to trigger the low coolant light, you should be alright.

Headgasket
 

Man I hope its not the headgasket. No noticeable increase in temp or decrease in power. Weather has been mild mid 40's to 50's How much would this set me back. The dim radiator can be fixed by cleaning contacts on the reservoir tank or side of radiator>? Thanks folks for all the input.... :o

describe in detail the amount of brown gunk, was it small beads floating around the top of the tank and sticking to sides? or was it like chocolate milK?

When you get around sixty-thousand miles it is not unusual to get small beads of oil in the coolant tank.

You can always do oil analysis of trans or engine oil to see if coolant has gotten transferred the other way which is more of an issue.

Gunk amount
 

The brown stuff smells like oil. It is on top the the green anti freeze. A little more that a few beads. It has coated the top of the plastic reservoir

also. have you ever used Redline Waterweter in you coolant system?

I bought it less than 1yr ago. It had 155,000 miles on it