Originally Posted by dcstep
Niels is right, it IS boiling and furthermore it will potentially ruin the pump. At the Advanced M-School at VIR in May, at least 1/3 of the M3 pumps failed. The mechanics would take the car to shed and it would reappear in an hour or so. Besides boiling out, it can deform some of the plastic parts in the pump, causing the pump to fail and you'll feel that in the steering reaction.
The fix is a heat shield between the headers and the pump. BMW doesn't do this to the school cars, much to the shagrin of all concerned, because they want all the cars totally stock.
If that's true then its a big design flaw. However, if 1/3 of M3s failed there I figure we would be finding a high incidence of PS pump failures among members here who track their M3s. AFAIK no one here has had to have their PS pump replaced so I am not that worried.