For MPS in 1.6.4 (I'm missing it in 1.7.10
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) you can install a cooling system on your chest piece and a heatsink on every piece of your powersuit. Or just one heatsink on your chest piece and max it out.
Last I did that when I was back on 1.6.4, I do not overheat even while flying in the nether. It cools off pretty well too even if I fell into lava, provided I got out of the lava in time.
Only few times I over heat was when I went ape crazy with the railgun. Or using the lightning generator twice in succession.
Edit: And I don't have the mps addons mod. Tried it and also from others whom have it too, having the kinetic generator will cause a lot of issues with death from overheating.
I'm not sure if it was fixed or not but I do not have issues with my powersuit running out of power.