For some time now, I've known that I'd need to replace my auxiliary water pump. When getting a flush and fill, they noted a couple of years ago that it was leaking. Also, I've noticed the last couple of winters the lack of heating capacity when at idle.

Fastforward to now.

I believe that I am detecting the smell of antifreeze from "inside" the car. Along with that, for some time, I believe I can hear water sloshing and/or gurgling in the dash area at a fast start/stop.

From these clues, who can tell me what is likely the culprit? I suppose what I'm really asking for is how the core and aux pump symptoms differ.

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1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles

The smell of coolant inside the car is almost always as a result of the heater core (inside car under dash) corroded to the point it leaks coolant. Lack of heat at idle usually indicates a non functioning aux pump.

You didn't say what car what year, but corroded and leaking heater cores are very common in 10 year old cars! My 85 190E heater core has been corroded for years, as is my 90 Volvo! My summer cars, no heat!

Repair will involve removal of the dash board and costly to do!

The gurgling is coming from the heater valve cycling, and can be normal in some cars at some ambient air temperatures. You are hearing the increased flow of coolant to the heater core as you come off idle, as your auxiliary pump is non-functional.
Smells inside the cabin are most often the result of something happening under the hood, not in the passenger compartment. Bear in mind that cabin air comes from just behind the hood, and particluarily on older cars the smells tend to escape the engine compartment to be drawn into the cabin inlet.
You said your auxiliary pump was leaking. I would replace it first. Look for any other coolant seepage under the hood. Then drive the car and see if the smell is still there. Chances are, if your heater core was leaking, you would get a film of coolant on the inside of your windshield after running your defrost for a while. They usually announce themselves rather obviously. You could also remove enough of the under dash and console to try to view the hose connections to the heater core. They could be seeping slightly.

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'96 C280 (gone)
'97 C36
'05 C230k

Ok, I haven't had time to r/r the aux water pump yet, but a conversation with an MB tech has me thinking.

First, he said that one problem (reduced heat at idle) could rather be a vacuum issue, as noticing a reduction in heat from a non-pumping aux pump would take a few minutes. Any comment on that?

Second, the gurgling is indeed getting worse, or more pronounced. I never notice it at speed -- only at idle, as just as I slow to a stop or accelerate. Whether I have a vacuum issue or not I don't know, but regardless, I think for sure that my aux pump is faulty.

Third -- the pump or heater core question. I did notice some leaking last week. Could that be from the core OR the pump, or is it more likely to be one or the other? Also, if the core was leaking -- would ANY of the leaking be to the inside of the car, or would it only drip under the car?

Basically, I'm trying to determine how many problems I have involving the pump, the core, and a vacuum issue.

I never, ever have any problem at speed. I don't notice any appreciable coolant loss. The coolant smell is very infrequent and mild whenever I do smell it.

All thoughts or constructive comments would be appreciated.

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1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles

My 1986 190E had a nice gurgling sound as well. Then one day the heater core exploded and dropped hot ass antifreeze all over my feet from out of the drivers side floor vent. No fun when driving 45-50 MPH on a three lane wide road! Burned the crap out of both feet and ankles as I attempted to cross three lanes, brake, and not blow the engine due to overheating. The heater core took me about 5 hours to replace, but I was also checking vacuum lines and wiring in the dash since I had it all out anyhow. Not really a bad job but you do need to remove the whole dash to get it. As for that aux pump, mine is dead and the heat is fine at idle. I am going to just take it out when I do my next flush and fill in the spring and put a piece of pipe in there to connect the two hoses. It is not worth the money to replace it unless you want the factory appearance and stuff under the hood.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

This is not what I wanted to hear Today, at complete rest, I noticed much gurgling -- not just when stopping or accelerating. Sounded like a Smurf taking a shower in there.

Also, car got a little hot while stopped for a while in a traffic jam. Wasn't able to tell if the aux fans were on or not. Will check that tomorrow.

__________________
1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles

Does Auxiliary Water Pump useful for reducing overheat?

I suggest that you fix your known issues as you find them, instead of collecting a stack of maladies and trying to fix them all through a message board post. You already know your aux. pump is leaking, so why not fix that and see whether or not it addresses your other issues?

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1989 300 SEL that mostly works, but needs TLC