The water pump is an item to preemptively replace at some interval of years and or miles. Most folks here will say to use only the OEM water pump with a composite impeller. I'm one of the heretics that went with the metal impeller water pump. The issue with the metal impeller, which you've pointed out, is that it will grind away the water pump cavity in the block if the bearing is worn to the point of the impeller contacting the block. Even a little wear can increase the cavity space to the point that the water pump no longer adequately pumps and circulates the coolant. My first water pump with a metal impeller started to fail and my temperature gauge light started blinking indicating I had a low coolant level condition. I was able to drive the car about 50 miles to get home. Then I had the car flatbed towed to my independent Porsche specialist. The bearing had started to leak, causing the low coolant condition, but it was not worn sufficiently to allow the impeller to come in contact with the block. Based on that I decided to again have a metal impeller water pump installed and I'll replace it proactively or the first sign of any coolant leakage around the bearing. The thing I don't like about the composite impeller is that it becomes brittle and cracks after some number of heating and cooling cycles. So you can have a chunk of impeller break off and get lodged in a cylinder head, which will cause a hot spot and ruin the engine. But I am very much in the minority on this opinion.
Good luck with your project!
Quote:
Originally Posted by xr_guys
On the donor engine. i found some water pump impeller debris inside the oil cooler. looks like the donor engine also suffer from water pump failure at some point. This issue of partial impeller getting lodge inside the engine is real. I opted to use metal version to avoid previous issue. I would rather have some gouges on my block than plastic debris stock somewhere inside my engine, just my opinion.
Thanks,
XR
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