Cross Coolant Pipe below expansions tank

I thought my problem was the hose that goes from the expansion tank down and makes a "T" but it's not. The "cross coolant pipe" that connects the two sides of the engine to the expansion tank and heating system has some small holes is it from an apparent leak. I am wondering if I can solder these or use some puddy product like muffler weld. I am trying to avoid replacing this part as I think the engine will have to be removed (or at least that's what bmw will do).