Hey Guys,

I just recently diagnosed a glycol/atf problem in my 03 c230 after all the well noted symptoms and turns out that I have 300 mg/l glycol contamination.

What do you guys think of an external transmission cooler and bypass the rad completely as opposed to replacing the rad all together. The vehicle is hitting 160k miles ans i dont intend to drive it forever.

The only concern is the harsh winter temperature in Toronto where the radiator might help keep the ATF slightly warm.....I am not sure if that should a concern ..any suggestions??

Sucks man... Hopefully you caught it before damage has been done.

I remember someone on the forum had an external cooler fitted in the passenger wheel well.
The heat from the engine might be enough to keep it warm, but we need to hear Glyn's advice on the operating temperatures I guess

Hi Ammar! Seems you have the faulty Valeo radiator. My suggestion would be to change over to the Behr radiator (they look different and there's the label to identify Behr). If price is a factor, then there's always a few C230 being parted out on kijiji in the GTA. Then ideally, you want to do a full coolant flush and full transmission flush, but a partial flush is better than nothing.

Like you said, you're not going to keep the car forever,... but who would want to buy a car with a Frankenstein external transmission cooler mod.

Harsh winter in Toronto??? Oh, we only had that huge ice storm, snowmageddon and polar vortex - and all that was just last winter! It can't get any worst can it? Usually quite mild,... at least compared to last winter.

I would not bypass, especially anywhere that gets cold.
The radiator heat exchanger helps warm up, cool and regulate the ATF temperature.


At a minimum you need a thermostat on the external cooler to keep from over cooling the ATF, and still will not have as consistent a ATF temp as a water cooled system provides.

A new Behr radiator is not expensive. It's designed to work with the transmission to control temperature. The TCU monitors TC etc. temperature constantly & varies flow via the cooler. If the transmission ever gets too hot it will finally kick down to a lower gear to increase engine RPM & thus transmission pump speed & fluid flow. Don't mess with this finely tuned circuit. It works very well.

Thanks guys for the input. Sunny, thats true there is always some one parting out the c230s and I might be one of those guys sooon

Glynn, I dont mean to dispute with what you said, we all consider you an authority over these things but i was just wondering wouldn't the external cooler work the same way as the Rad, especially the self regulating ones and TCU should work the way it normally would.

Say in the summer time, the appropriate size external cooler in my opinion should perform better because of the available increased surface area to cool down as opposed to the rad where the tranny fluid is not quite routed through a large surface area. And in the winter time self regulating cooler would only allow fluid to pass through the larger cooler once it heats up and reaches a certain viscosity and the engine heat is always there to aid with the process........

There's someone in AMG forum with an external cooler: https://mbworld.org/forums/c32-amg-c...r-mounted.html
Perhaps you can PM him and ask questions if he's still around.

The issue is that an oil to air intercooler is not as efficient as a oil to water intercooler, so the total surface area the ATF fluid has to pass over is bigger.


Then is it is designed to cool enough in the summer it will be way too big in the winter, thus requiring a thermostat (and it has to be a bypass thermostat since you can't just block the flow.


Next ATF fluid output temperature varies widely with load, and the water in the radiator moderate the temperature changes to help keep the return fluid to the pan at an even temp.


Last, during warm up, and during very lightly loaded operation the radiator water temp may be above the ATF temp and actually heat the ATF to keep it at its proper minimum operating temperature.

+1^

The only way to spec an external cooler is to overspec it. It's unlikely you will ever achieve the control that the standard system achieves.

If you were constantly operating in low speed, high torque situations it might make some sense ~ but you are not. If you were Benz would have designed for it.

Thanks guys for the valuable input. I guess new rad it is then based on the expert opinion.... could you guys give me an idea for the shop labour hours on this kinda job before i talk to my mechanic. Thanks a bunch again.

it's good and bad idea how will you know if your transmisión is operating at the correct coolingc temp. Plus you can start having minor problems with the transmisión you do not need . I have a brandy ne set in my garage. I have 1998c230 over 300 mil i replaced the valve body once in original transmisión. And engine.
garaje.buy a new radiador it's cheaper or just sell me the car ivwill fix it