I did seeon the my friend's car theradiator that was leaking from time to time.. Just an observation from the past experience.

 

only problem with a radiator leak is its under pressure all the time so would leak all the time, the pump has a pressure release valve when the bearing goes and mostly leaks when car is standing but saying that you could be equally right because its just a tech guess and a guide

 

Thanks a lot for the fantastic response!!!

So did I get it right, I better first try bleeding the system or could it be that my water pump is going?!?
The heating works fine and the temperature stays directly in the middle of the scale.

Another big note though!
Today I drowe home after work, 15 miles or so and when I stopped the car it kept a considerable "hissing" noise. Looked underneath the bonnet and I figure the noise was coming from coolant reservoir. This would support that there were/is excessair somewhere or??

Thanks again you all.

BTW, anything special bleeding this 4.2 engine? I guess it will go with the instructions I found on this site for the other engines? And yes, I will stick with the red G12 fluids.

 

Just a late update.

The problem turned out to be a small crack in the expansion reservoir that started leaking once the fluid was hot and viscosity low enough to escape under pressure.
In other words I was surely loosing that also when driving but as the distances had lately been relatively short, the puddle underneath the car was large part of fluid lost.

Thank you all for your comments and help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

could be the secondary water pump. i didnt know i had one until my guy informed me there was a slight seepage on it. i think its hard to see unless the car is on a rack and partially disassembled.

 

I recenlty had a problem like that. Coolant was dripping peroidicly. Found out that the coolant was dripping from the oil cooler onto one of the radiator lines. I had a cracked oil cooler.

 

Glad you got it figured out. there are tw main causes for such a leak in our car
1- the expansion tank which is cheap. I think ECS Tuning had them for $25 a while back.
2- the aux water pump which is more a pain to replace and pricier.

glad to know it was #1 for you. Sorry I did not see your thread earlier, I coud ahve told you those 2 things sooner

 

Glad you got it fixed and didn't have any more serious problems. For future reference, the 4.2 only has the mechanical pump and the 2.7 has two pumps.