60,000 mi
07-27-2015 | 11:18 PM
#16
Rennlist Member
Joined: May 2013
Posts: 2,110
Likes: 471
From: Miami
As a fellow tech, I completely agree with the plastic impeller being a much wiser idea from the factory (for once).
I've never seen plastic versions just fail from being plastic. There is almost always excessive play in the bearing which allows the belt tension to slowly pull the pulley upwards until the angle finally causes a leak or the bearing locks completely. While this is happening, the impellers may start to contact inner housing causing them to break away. But, they are almost always intact when pumps are replaced for bearing failure.
Also, as a dealer tech, I disagree with 997.1 pumps not failing. We see them regularly enough, and mine failed at 35k. Known issue and being proactive can save you from a more drastic failure, while not leaving you stranded and/or dumping coolant until you possibly overheat the car. Problem is, every car is different, driven differently, and in different climates. Needs to be done sooner or later no matter which route you choose. And always replace the thermostat at the same time.
I've never seen plastic versions just fail from being plastic. There is almost always excessive play in the bearing which allows the belt tension to slowly pull the pulley upwards until the angle finally causes a leak or the bearing locks completely. While this is happening, the impellers may start to contact inner housing causing them to break away. But, they are almost always intact when pumps are replaced for bearing failure.
Also, as a dealer tech, I disagree with 997.1 pumps not failing. We see them regularly enough, and mine failed at 35k. Known issue and being proactive can save you from a more drastic failure, while not leaving you stranded and/or dumping coolant until you possibly overheat the car. Problem is, every car is different, driven differently, and in different climates. Needs to be done sooner or later no matter which route you choose. And always replace the thermostat at the same time.
07-28-2015 | 12:09 AM
#17
Racer
Joined: May 2012
Posts: 342
Likes: 72
I've never felt they were necessary, but don't see them as a negative. Opening sooner during warm up cycle doesn't equate to better overall cooling in my experience. Thermal efficiency, as in using a third radiator and not having a weak/sticking thermostat (especially the secondary spring in these cars), always makes the biggest difference.