@ShocknAwe
Based on the
limited testing done the EKPM2 appears to dissipate less power than the EKPM3 at the same pump current. So the EKPM2 should not get as hot. You shouldn't throw away your EKPM3, however. The power dissipated is not enormous even if it is about 43% more than the EKPM2. Getting that heat out of the components and into the ambient environment is key.
In all cases the thermal gap pad should be changed between the EKP circuit board and the base plate. See
post 84 for a recommended pad, though other pads will work too. You want something thin (0.5 mm) with a high thermal conductivity (near 16 W/m-K). This pad must be non-conductive.
For all other thermal interfaces where a pad or grease is needed the pad can be conductive (its typically metal-on-metal anyway). This opens the opportunity for graphite pads to be used. Pay attention to the thru-plane thermal conductivity. Grease is probably best because then it is only as think as it needs to be, but grease can be messy. Any place where two surfaces touch use thermal pads or grease to lower thermal resistance.
Heat sinks may or may not be necessary. If using a heat sink orient the fins so the channels between them are vertical. This will allow convection currents to naturally rise through the channels and increase cooling.
In
post 84 I added the heat sink directly to the base plate of the EKP, and
@NoGuru added a heat sink to the bottom of the mounting bracket in
post 97. If adding the heat sink to the bracket it is important to put a thermal pad or grease between the EKP base and the mounting bracket to reduce resistance to heat flow. Ideally the thermal pad or grease would cover the entire mounting surface between the EKP and bracket.
Other chassis have the EKP mounted differently. In the case of an E89 it looks like the chassis itself could be the heat sink with thermal pad or grease between the EKP base plate and the chassis. On the E93 space is tight so a 1/8" x 2" aluminum bar may fit between the EKP and the mounting bracket (with thermal grease or a pad between the EKP and the bar) with the ends extending beyond the module, the longer the better (insert joke here) to increase surface area. Heat sinks could be added to the bar to further increase surface area as space allows (with thermal grease or a pad, of course).
If you want active cooling, stick a fan on the heat sink. Connect the fan power leads to the power input to the module (constant speed) or the power output to the pump (variable speed).
You can put heat sinks on the cases of the components and add a fan to the housing as in
post 7, but the parts and the module are designed to flow heat through the circuit board and into the base plate. You probably don't really need the heat sinks in this instance because I suspect most of the heat will be coming off of the PCB as the heat in the components can flow more easily into the PCB than through the component case (lower thermal resistance from the junction to board than from the junction to case). Cut holes in the housing near the connector to allow the hot air to escape. The side near the connector is the hot side.
Changing the switch in the EKPM3 did reduce the power dissipation, but it never got below the EKPM2 so the recommendation here is to buy an EKPM2.
In the end the correct modification is the one that works for you. The exception is the thermal pad between the PCB and base plate. That should always be changed.
