I have the slow, frustrating, smelly coolant leak again and I can't see anything that indicates coolant loss on the engine. What are the symptoms of an evaporator failure? The car is my '94 E320 wagon with 223,004 miles on it.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

Don't know, but put three candles lit tonight to the Evaporator gods and hope it isn't... dash removel, labor $$$.... Sorry I am no help, but atleast I posted a response for you and bump it up

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1995 E320 smoke silver / parchment

Coolant?...do you mean radiator? The evaporator is a problem with these cars. However, your description sounds more like a water coolant leak and NOT an evaporator leak since that has to do with the AC. Do you have oil in your water reservoir?

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J.H.
'86 300E

Hi JH, There is no oil in the coolant tank nor water in the oil. What substance flows through the evaporator? Coolant or freon? I've heard that the evaporator is the same as the heater core on other cars. Is this accurate?

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

Refrigerant runs through the evaporator not coolant. Coolant is the substance used in the radiator and engine for engine cooling. Refrigerant is used in the a/c system for cabin cooling.

The "symptoms" of a bad evaporator are the same as symptoms for any other a/c system component failure, loss of cabin cooling via a leak. There are many sources of leaks. If you determine that there is a leak due to the need for adding refrigerant, then it is time to diagnose the leak. At that point, the evaporator may be found to be the culprit.

If you are smelling coolant in the cabin this has nothing to do with the a/c. Is the a/c system cooling the cabin okay? If not, is it due to low refrigerant? If so, search for the leak.

Good luck,

The evaporator might look like a small radiator it uses freon from the compesssor routed to the condenser (front of radiator).
The gas is compressed producing heat, that heat is ciculated thru the condenser, when is is released it does the reverse and produces cold which is circulated thru the evaporator, and the process starts again at the compressor. I left out all the other devices such as dryer, safety switches, expansion valve, etc.

If you are getting a coolant smell inside the car you could have a lesk at your heater core or at the pipes going into the heater core. Replacing the heater core isn't quite as labor intensive as the A/C evaporator the dash still has to come out to gain access to it.

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Mercedes Benz Master Tech - Retired

Thanks guys. With 223, 000 miles I should expect failure of some hoses that are probably still original but I've already replaced a number of them. I appreciate the education on evaporators. I've still got a lot to learn!

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

If your car is still cooling I doubt it is the AC.

The AC on my 92 300e went out 2 years ago at 125,000. They checked for leaks first to determine if a faulty hose and not the evaporator.

Why? mine was the evaporator - which requires the dash be pulled and a $2,800 bill. Local indie did it for $1700 which included replacing the pods.

Hope yours is not the evaporator.

[QUOTE]Originally posted by LarryBible
[B]Refrigerant runs through the evaporator not coolant. Coolant is the substance used in the radiator and engine for engine cooling. Refrigerant is used in the a/c system for cabin cooling.

Thinking about this more I realized how stupid I am - of course I knew the function of the evaporator and that hot coolant couldn't possibly run through it to cool the car! What an idiot! It is a testament to the class and diginity of the people who replied to this message that they didn't point out my stupidity to me but instead chose to educate me. Thanks guys.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

Not being aware of something does not mean you are stupid. It just means that it is knowledge that you have yet to learn. That's why we ask questions, so we can learn.

Have a great day,