I had slow leaks in the front end of the hard pipes as well. So slow as not to show on the driveway but I got a Harbor Freight Pressure tester and pumped the system up to 13 psi I believe and came back a bit later to find it had lost a pound or two of pressure. I kept topping off the reservoir until I changed the hoses and hard pipes while doing a larger repair and the problem became obvious when I looked at the ends of the hard pipes.

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2001 x5 3.0 (sold with broken motor), 1990 e30 M3, 1991 318is, 2002 325i, 2008 335i Dinan stage 3 6 speed,