read the posts and felt had to post.what you are all missing is this.mercedes radiators are made of plastic and aluminium and as they age[6-8yrs]two things happen.1 the plastic petrifies[meaning that when you fix a hole a new one will arise to take it's place].2 over temperature cycles the aluminium core will shrink and cut down on the quantity of water moving through the tubes.a classic case of this is sitting at idle foot on brake car in drive ac on and temp starts to rise but when you hit the gas and take off[speeding up engine and therefore water pump]you can watch the gauge drop.if you dont want to be constantly fixing the cooling system and maybe an engine bite the bullet and buy a new radiator. david poole owner european performance dallas texas