Leaky Radiator Core?

[nate13]

Hey all, long time no post.

I've been going through a rebuild (far past a refresh!) on my Auto 3.0L for the last few weeks after experiencing a pretty gruesome CCV failure. While I'm in there, I figured now is the time to address the OFHG and the core of the cooling system since I've had very slow coolant loss for the last 3 months.

After removing the fan and the shroud, I noticed some white spots on the radiator core, and on the radiator shroud (corresponding to one of the radiator spots). I've never seen this before, where my e46 had a leak from the expansion tank side plastic end cap a few years ago. Looking for a consensus- tell tale radiator core failure? or did I drive through some white crap and it just stuck to the radiator? Or..?

[David.X5]

Fluorescent dye in the coolant is a cheap/easy way to know. I wouldn't act on that stain until you find sign of an actual leak (pinhole, bent tube, etc). If you can fill and pressurize the cooling system, I would try the dye. If the car is apart already, you have less choices.

[nate13]

I read a few places to stay away from Fluorescent dye in the system, but didn't find much evidence supporting this view.

I ordered, and reccomend, the Motive power bleeder, and the associated adapter hose, to test pressurizing the cooling system. There was no evidence of leaking coolant when I did this on the X, but it did lose pressure (5/lbs/hr).

I did end up ordering a new radiator regardless, since I was redoing the rest of the cooling system anyway. I'll update with a definitive slow leak test (lay on it's side, fill with water, look for spots), and some more pics. Anyone else ever have core leaks on their radiator? I've never seen this before.