My '91 420SEL (W126) is only an occasional-use car, and as I was pulling into the garage last weekend, it was dripping a pretty large amount of coolant (more like a small stream).

Looking from underneath, it was dripping from the general area of the oil pan, but I couldn't really see where the leak location was. It MAY have been dripping down mostly over the rear portion of the oil pan, but drops and little streams were coming from multiple spots.

From above, I could see no signs of anything. No sign of any issue with the radiator, nor with the main radiator hoses.

I need to really get underneath the car to look more closely, but would welcome suggestions as to possible leak causes or locations that might drip down past the oil pan. Is it possible that a freeze plug or drain-location on the block itself would just fail suddenly? Because it was streaming pretty good, but at the same time there was no "drip trail" on the lower part of my driveway, nor the street. So I think it basically happened suddenly. Are there heater-related hoses in this general area?

I looked in the general area of the mono-valve (valve that controls the flow of hot coolant into the heater core), but saw no signs of leaks there.

I suppose another possibility is some form of head gasket failure, but for the short time the car was running before I turned it off, I didn't see any white-smoke evidence of coolant getting into the combustion chamber. I have not yet checked for either coolant in the oil, or oil in the coolant...

 

did you check the water pump area around where the belt pully connects to the actual pump? Usually mid way along the pump around the pump shaft area. There is a few holes in the housing of the water pump, guess for air circulation. The internal gaskets fails and cause coolant loss through those holes. These drips can creep along the towards the back of the water pump and drip around the oil pan area, especially when the car is in motion. And those can be fine one day and fail the next. Quite common failure in cars that sit for long periods of time and or rarely driven.

 

or another way to trace the leak is using a coolant UV dye and blacklight.

 

Thanks for the suggestions - I'll check out the area around the water pump more throughly - although at first glance it didn't seem to be coming from there. Whatever it was, it was definitely sudden....

 

yeah it happens like that sometimes. Usually all of a sudden is a gasket finally giving out from the coolant pressure. It's not too unusual.