Cool Beans
Back on the MK2, I’ve mostly figured out the cooling system.
Unsurprisingly, the stock BMW system is more complicated than the LS or the 5MGE. The M52TU is shown below but it is largely the same between the the M54 and M52TU. It uses an expansion tank as well as an additional exit port on the engine. Unlike the LS/5M, the heater core runs back to an expansion tank rather than to the engine or water pump. In the E39, a secondary water pump is used to circulate coolant when the engine isn’t running. This helps keep the heater core warm when the car is parked.
Originally, I hoped to use an E46 radiator and expansion tank. Contrary to internet lore, these parts were quite reliable in my old 330i and easily went 100k miles on a DD street/track car without issues. I bought a cheapo eBay E46M radiator and some OEM 330i hoses and tank but they just didn’t fit how I wanted. Radiator was the perfect size though.
After some measuring, I took the plunge on another eBay/China Nissan S14 240sx radiator. I would never run something like this on my M3 but the stakes are a little lower with this engine. If it leaks, I can buy a Koyo and swap the integration parts. I had a 3 core version of this radiator with the LS and never had cooling issues. This is the lighter 2 core version. I designed some brackets to utilize the stock mounting points and had SendCutSend make them.
Some minor radiator mods were needed to make an E39 lower hose work. I also added a 5/8in barb for the heater core return. The upper hose is a trimmed SN95 Mustang upper and the lower is stock E39 M54. I cut the quick disconnects off some OE hoses to adapt to the M54 outlets. This also allows me to use the stock M54 coolant temp sensor.
Next, I cut, sleeved, and re-routed the stock coolant pipes for the heater. I will need to get better pictures of this stuff when it’s off the motor and cleaned up. You can see the ITB actuator bracket that I designed as well. These will require some PA6 3D printed clips to keep everything in place. A little more cleaning up is needed here.
RRD sells an ITB actuator mount to go with the ITB adapter. However, it did not look to clear heater hoses and I figured that I could do better for less money. After much measuring, scanning, and CAD, I came up with the one below. 3D printed a check part from PLA before ordering standoffs and getting the plate cut.
The last major portion of the cooling system was the fan. I bought a Spal 13in/1777CFM puller which should be enough. Modeled everything up as it was far quicker than scanning and designed some brackets. The parts below are PLA check pieces. I will get these made from .09in aluminum.
Power steering, fuel system changes, and wiring are next.
