I recently purchased a 1994 E220 from a dealership, which runs well most of the time. I have noticed on a couple of occasions that the temperature guage rises to around 100 - 105 on days where the outside temperature is above 30 degrees celcius.
I did notice coolant dripping under the vehicle, but this is very intermittent. The coolant in the reserve drops when this occurs, and i have ensured to check on the level twice a week. No leak has occurred for a month now, but occasionally the guage still rises.
I have never seen the thermo fan at the front of the radiator in operation, even when i let the engine run at normal temperature in the driveway for 15 minutes.
At the last service, the mechanic noted on the report that it was evident coolant had leaked down the rear of the engine block, as well as minor oil leaks on the side. As the car runs at normal temperatures 99% of the time, it is difficult to demonstate to the dealership where i bought the car. The oil and coolant are both clear.
Is there any obvious reason for the occasional overheating? The dealer insists it is not a head gasket, as the oil and coolant are not contaminated. Will a pressure test show up a leak ?
I am keen to have the problem rectified now, as the car is covered by a warranty for defects which occur within the first 5000 km's.

 

On my car, a '92 400E on a hot day with the a/c on while stopped or in traffic the engine does tend to get a bit up there on the temp. guage. As soon as it hits the three quarter mark the fans do come on and cool it down to the half way point then shut off, and eventually the cycle repeats. I don't know if the fans can cool the engine down that much or if the themostat gets involved as well, but when those fans come on they are loud! They must move a ton of air through the radiator to cool it. If your fan does not come on then that might be the only problem because a broken thermostat would have larger problems arise. My car also leaks water and the light goes on about every three weeks or so and has two electric fans in front and the single belt driven in the back.

 

Hi,

it is hard to locate leaks in the coolant circuit ,since coolant leaking through minor leaks just evaporate before dripping else where. A pressure test would show if there are leaks. If you locate the leaks on the left rear of the engine block, it could come from the connection from the block to the heater radiator behind the dashboard.
A blown head gasket would not show leaking water under the car, it would just burn inthe cylinders (and possibly cause white steam coming out of the muffler)

However it may also have to do with the aux. fan(s) of the A/C radiator. If this does not come on, the engine radiator sees much higher temperatures during A/C running, and could cause the occasional "overheating" since the A/C radiator sits in front of the engine radiator. Check the fuses first and than the thermoswitches.

If the main radiator fan does not come on during high temperature it sounds like the shot thermoswitch.

Minor oil leaks are no big deal and dont need much attention, say upto 1.5 liters per 1000-1500 km is quiet ok.

 

wow, you guys are daring, I would never allow my engine leaks, not the radiator (coolant) too.

In my country, most of the tyre shops have a type of machine to "wash" or flush your radiator. I do recommend you get your radiator "washed" and get the mechanic to check more thoroughly on all the connecting hosts between the engine and radiator. I got my radiator leaking problem solved by changing the 2 rubber host and get the temp down after the wash.

Of course your fans must work too. 100 degree celcius is just too high right ? Mine engine usually stays at 82-85 deg. At once it went up to 100 degree after I parked the car under 35-40 deg environment (under hot sun) for more than 20 minutes while my kid was sleeping in it with air-cond turned on.

Engine leaking is normally caused by the oil seal being hardened, ageing problem. That does not cost you a lot to fix. I spend US$20 to fix that last week.