Join Date: Aug 2005
Location: Arlington Texas
Nobody is really sure which comes first, the coolant bottle leak or the cracked tank.
One theory is that air admittance due to a cracked tank or bad tank to filler neck seal (it's a 2 piece design with a gasket seal) causes a water hammer effect that cracks the tanks.
In my case, it was the filler neck seal that let go and it was such a small leak I never saw it until one very hot day out in the desert when I heard the leak and found that the noise stopped if I pressed on the filler neck at a certain point. A tiny speck of dried sodium silicate where the filler neck met the bottle indicated where the pinhole leak was. I mistook it for glue before I heard the noise!
I went through THREE radiators with that bottle....this rad is holding with the new bottle.
2004 300M Special...257K miles. Original powertrain!