[MarinerZ4C]

My 2006 Z4 Coupe is sixteen years old, and I want to maintain it as a reliable and fun ride for many years to come. It's in excellent shape overall, at 82K miles, but I have experience with aging BMW cooling system parts from my 325xi and 128i ownerships.

I’m planning a complete cooling system refresh this late Fall or Winter, when I should be up to about 90K miles. Choosing which radiator is not as simple as I had thought. I don't have a core depth dimension for the Genuine BMW radiator, but I note that my aftermarket choices have differing core DEPTH (thickness) dimensions. A blog by FCP Euro on changing a radiator on N52 BMW’s claims Mahle/Behr is the OE, and the depth of the core for the radiator I find recommended for Z4’s is 32mm (1 ¼ inches). Nissens makes a similar radiator with a 32mm core depth, and FCP Euro sells it for Z4’s. But the Nissens catalog on line does not recommend it for N52 Z4’s but instead specifies a different part number with a core depth of only 22mm (7/8 inches) – carried by RockAuto (who also sell a Behr/Clevite part 32mm thick).

Vendors sell two different part number Nissens radiators for the same Z4 application – but Nissens recommends only the thinner of the two for my Z4 Coupe. Do I need the added clearance between motor and fan shroud ? Comments about the CSF 3055 2-row performance radiator discuss fitment issues because of reduced clearance – but it’s even thicker, so I might expect that. I would normally lean to the thickest core that fits . . . .

If you have been down this path, please share comments on what radiator you chose as a replacement on your N52 (LCI) E85 Roadster or E86 Coupe.