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Heater Core Leak?

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I have a problem with my 1989 190E 2.6L gas/auto.

I shut the car off after a system test, and suddenly an amazing amount of antifreeze starts pouring out from my transmission pan.
I figure that it is leaking onto the trans from above and running all over it. My car is on a tilted driveway, with headlights pointing up a bit. I suspect the heater core, though I dont have any wet carpet or that familiar sweet smell indoors, its all outdoors.

I was charging the A/C and making sure the HVAC modulation from hot to cold was good, and it was. I then shut it off, and waterfall!

Could it be a rubber hose? Do Heater cores go bad often? Is it hard to change? How expensive is it?

Any details are appreciated.
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'01-E320 & 02-ST2
31,798 Posts
Yikes, Prevost.

By "transmission pan" do you mean the metal inspection cover/dust plate that covers the bottom part of the gap between the engine and transmission? If so you might have a corroded out freeze plug if you can't see an external leak. I hope it's the latter, but you'll only know by a thorough inspection. (I'm pretty sure there are freeze plugs in the back of the engine block, to replace them you'd have to remove the engine and pull the torque converter and flex-plate, that's why an external leak would be much preferred!)

I've not changed a heater core on a benz, but on the other cars I did they were in the dash or a container box the protruded into the engine compartment, but in both cases they leaked coolant into the passenger compartment.

If you're entirely sure it was engine coolant, be sure to get it thoroughly inspected, a pressure/leakdown test is the best way to isolate it. Since you were testing and charging the AC, is is possible it was just dirty evap water? Often the drains for those plug up and then it overflows, that might wash down the side of the transmission.

If you do the pressure test yourself (I think that might be one of the tools Autozone lends) then pull the inspection/dust plate off so you can see up in there in case it is coming from there.

Good luck and enjoy the ride,

1989 190E 2.6L Auto
36 Posts
Discussion Starter · #3 ·
Hey man thanks for the quick reply.

I am a little wiser on the subject now.

I went to a junkyard and saw that area without the motor and trans. There is a condensate drain that protrudes there beneath the HVAC area. It has 2 drains and I am 99% sure that is where the coolant is coming from. The car was tilted upward so it ran all over the trans and rained down all over. I have disconnected the electric water pump which curiously had 3.7 volts to it while the engine ran. It leaked less water without the pump running. It still leaks. I read up a bit on it and it seems like quite a chore. I am sure glad its spring and Ive got time to bypass it until winter comes.

Do I cap the lines or install a bypass hose?
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