545svk

I removed my water pump, and the impeller is loose on the shaft.
I don't see a brand on it, but there is a part # 928 106 140 OR and another # 7533F2
The impeller has a part # 928 106 053 00 and was made in Germany.
The impeller doesn't look worn where it fits over the shaft, but it is a loose fit.

If this is the cause of my overheating issue, then why was both the inlet and outlet hoses hot to the touch?

Some images:

JET951

That is what happens eventually happens to water pumps with plastic impellers , the plastic degrades over the years and thousands of heat cycles and the plastic impeller falls off ( its not meant to come off ) , we have seen lots of them in varying degrees of "Plastic Degradation " , be it the entire plastic impeller falling off ( like this 928 water pump ) or the impeller blades them selves coming off individually , like we have seen on Boxsters , 996 and 997 etc , in the case of the plastic impeller blades breaking off , the broken bits are often never seen again , so if a plastic water pump impeller is to fail , I would rather see the entire impeller to come off in one piece

With the 928 series , its always wise to replace the water pump at every cam belt replacement interval , meaning every 6 or so years or every 60,000kms ( city / suburban use ) , that way you can avoid water pump issues

PS } I still remember seeing the first one ( plastic 928 water pump impeller separated from the pump like in the photos above ) on a 928GTS ( factory Porsche water pump ) around 20 years ago , since then we have lots more & not just on Porsche's but other cars as well

Regards
Bruce Buchanan
Buchanan Automotive

FredR

This has happened to me twice- once just after I acquired my S4 and again about 5 years ago.

If the coolant is not flowing it heats up by conduction and there will be little to no cooling effect across the radiator unless there is a natural thermosyphon effect that might result in a little cooling. When it happens in 44C heat with the ac operating the temeprature goes up like a Saturn 5 rocket and you need to catch it quickly. In cooler weather [25C ambient] I found I had more time and it did not go up quite so quickly but I immediately knew something was wrong. Fortuately I was a couple of minutes from home the 2nd time around.

545svk

Thanks guys.
When my "issues" started it was around 20 degrees Celsius, And about 10 min from home and a cold start.
So it looks like I found my initial problem: I assume the car simply "boiled over" - coolant escaping via the overflow because the heat opened the radiator cap pressure valve.

Other people would most likely have removed the water pump before the heads.

However, with all the threads around head gaskets, I'm glad I pulled mine. My gaskets were shot, but the heads aren't warped, and with very minor pitting. If I didn't do it now, it would have bothered me and I would have had to do it in the near future in any case.

And now I have lots of time to clean where I couldn't reach before while I wait for the slow boat to bring my parts.

FredR

Dawid,

I advised you earlier that even if the heads were not the root cause of your overheating then pulling them would be a sensible action in its own right if they have not been removed previously and your findings prove that even though you arguably may have jumped in a bit premptively. In taking the actions you have you can be reasonably sure you are going to be OK for a fair few years.

What is the latest on the heads?