mayo in the rad

[tonycott]

Hi all

Got a P reg Mercedes W202 C200 sport, noticed that there is a lot of mayo/cream in the rad, this usually equals a blown head gasket but i was thinking the gearbox oil also runs through the rad to. So is there any way of checking if its engine oil or gear box oil before I have to get he head taken off.

[jaybkay]

Not so fast, it maybe that the engine isn't running hot enough. make sure the thermostat is working (and a hot one for winter), and take the car for a good run.

[GreenV8S]

I can't think of an easy way to tell. You can pressurise the cooling system and see whether either the gearbox or engine sump start filling up with water, but obviously that's going to then need work to get rid of the water/oil mix and replace with good oil. Some cars have a dipstick/fill point for the 'box. If yours is one of these then you could look for signs of mayo in the 'box. Otherwise it's going to be tricky. I guess the trans cooler is fed by hoses in which case you could clamp supply and return off and see whether a coolant pressure test shows a leak, or you could disconnect it completely and do your pressure test again, if you get coolant dribbling out of the oil supply/return spigots you know that's your problem.

You may also find if you do a cooling system pressure test that you can hear where the escape is. Not always possible but sometimes you get lucky.