Check your fuses i dunno why the heat would effect it but when you pull your hicas fuse you lose power steering..
Here is a nice little trick;
In the boot there is a HICAS computer it hangs of the rear parcel shelf.
There are 2 sets of wires going into it one larger and one smaller.
Unplug the smaller set of wires leaving the larger set connected.
You have now disabled hicas..
I've had this done to my car for the last 30,000km and seen no side effects, i've even driven on the race track and its been fine.