Hi all. Quick introduction - new to the MB world, just picked up a 97 S600 recently that won't be here long (it's a repo that has to be sold) but needs to be fixed before I sell it. I'm no stranger to DIY work - my "fun" car is a 1972 911 which I do pretty much all the work on myself. However this issue involves coolant, which is a completely foreign thing to me, knowing air-cooled cars only.

The other day the car sprung a coolant leak while driving - smoke everywhere, had to get it towed home. I got under it tonight, removed the plastic front cover under the front of the engine and had a good look around. Everything inboard of the passenger wheel is soaked in coolant, and that's where it's been weeping from - basically below the coolant tank. However on the upper side, everything's dry, except the braided overflow hose, which looks like it's just absorbed spray, nothing more. There's a bit of coolant pooling on top of the engine (see pic below).

On the advice of a mechanic friend, I topped up the coolant with water and fired it up, to see if I could see where it's leaking from. It ran fine until the temp gauge reached 100C, then the 2 front fans came on. About 2 minutes later it started smoking hard from the rear driver's side of the engine (circled area in 2nd pic). I looked underneath and there was a slow drip from about under where the pedals would be.

Is this something I can DIY? Or does it need to be taken to a shop/dealer for repair?

Thanks for any help!

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bump - anyone have any ideas?

Fire it up and use a telescoping mirror to look in there and see where the leak is coming from (preferrably before the smoking starts).

It could be varying levels of difficulty, but that general engine region usually indicates the hose to the heater core.

Good Luck!

Thanks - I'll try that. A hose would definitely be good news, rather than something internal to the engine.

One further question, perhaps stupid, but as I said I'm an air-cooled guy and this coolant stuff is new to me: does the coolant system only fire up once a certain temperature is reached? When I ran the car the other day to test it, after the 2 smaller fans started (as it hit 100 degree), it seemed that the smoke seemed to start very abruptly, rather than gradually.

Thanks.

Water pumps through the engine block and heater core at all temperatures.

At 87 degrees celsius, the thermostat should open. Then coolant should be pumping through the entire system.

So if you're at 100 degrees celsius, the fans are definitely supposed to come-on. You may be air-locked, so open any breather screws (top of thermostat housing or radiator) to let air escape, while simultaneously topping off with distilled water in the reservoir. DO NOT USE green coolant in that car. Use zerex Z-05 or mercedes coolant only.

Do this before you start the car, and again just after starting. The water pump will push out a lot of the air for you.

Then you will have enough coolant to hopefully keep your car at operating temp while you inspect the leak.

Good Luck!

Great stuff - thanks!