i had a simlialr problem with mine
driving to italy my fluid turned to pink foam and blew out teh breather all down the side of the car
then a pipe failed, i kept changing the fluid but it just went pink and foamy
anyway changed the pump, its a TD5 so the pump and water pump share the same drive, when i took the PAS pump off the water pump was all gooey and rusty and then i started leaking water, think water was seeping into the pas pump somehow, anyway both were changed and the problem solved
maybe someone with more knowledge can explain better?