[Frodo]

Originally Posted by Steve Tinker

Hi Doug - looks like your preventative maintenance is keeping you busy.
As to the damaged impeller, does the damage look like an actual breakage or erosion of the plastic - difficult to see from here. How many miles /years has the pump done? I bet you were losing 25% of your coolant flow looking at the impeller vanes......

If its erosion, there shouldn't be a problem, but if bits have actually snapped off, then the debris could still be in the system. The first place I would look ('cos its easy) is in the thermostat housing to see if the thermostat has stopped the damaged bits from circulating. I think Jeff (JFP in PA) has suggested in the past to "back flush" the system to make sure any loose bits are flushed out before bolting back together - how difficult this is I'm not sure but its probably easier and cheaper than having a coolant blockage in the cylinder heads.

I'm sure one of the professionals with more experience than me will chime in with some good advice...

As to your question, How would you distinguish between "actual breakage or erosion"? The exposed edges (where the small amount of plastic has disappeared) are roughened---don't know if that tells us anything. The optimist in me says that erosion would do that, that if the pieces suddenly were snapped of they'd leave an irregular but smooth edge. Does that make sense?

I did take off the thermostat, and saw no parts in or around it, or the pump.

I'm not really sure about how to go about back-flushing the system. If anybody knows of (or wants to create---your good deed for the week!) a DIY, I'd be all ears.

I assume it's the original pump. I'm the second owner. Car has 57K miles; got it in 2005 with 19K miles.