Kevin in Atlanta

Breaking done a 91 s4 for head gasket replacement. I was testing the waterpump bearings by spinning the pulley back and forth and I could hear a rattle that I assumed was a loose impeller. I was wrong. This what we found behind the waterpump.

It is the inner thermostat seal sans the rubber coating.

Bill Ball

Usually that seal is almost welded to the waterbridge and requires extensive prying to dislodge. Must not have been seated very well.

Kevin in Atlanta

The one I replaced was still in place and you are right they get mangled in the process of being removed. So, I agree this one was never seated and floated off. Wonder how long it has been there?

worf928

Looks like the ribbed rubber coating is gone?

Kevin in Atlanta

The rubber is gone and the rear surface has been worn away - the block is nice and shiny.

SteveG

How ever it was seated, how could this happen? I mean wouldn't it leak if it was not in position? Could water erode the rubber clean off (sic)?

worf928

Yes, one needs to be concerned with what was circulated in the block that caused the rubber coating to "go away"

mike77

Might want to look at Dwaynes coolant bridge refresh writeup. I did mine last year. I found my seal not much better than that and other seals on the coolant bridge were in poor state also. You can also get the oil filler gasket at the same time.


Edit: just read your post again and see you are breaking the engine down for headgasket. You've probably got stuff like above covered already.

Imo000

This could have been in there from before you did any work in it. All the stars lined up and it eventually made it's way to the pump.

mike77

The plastic on mine was very brittle and completely came away from the metal ring when I removed it. Perhaps a previous owner dropped it and couldn't fish it out then it spun around the cooling system like a washing machine cleaning off the brittle plastic.

Imo000

What plastic?

mike77

Didn't that metal ring look like this when it was new?

http://thumbs.ebaystatic.com/images/g/w7AAAOSwKrhVWubW/s-l225.jpg

Imo000

Where is the plastic?

bureau13

It's some kind of coating, plastic, rubber, I don't know. When I changed mine out, I thought it was missing, because all of that coating or whatever it is had been eaten away, and it was just a silver metal ring that was all but invisible.

I'm pretty sure my thermostat was fine, and that seal was the problem, so I too wonder how long they last.

Imo000

They are normally stamped mild steel with a coating of rubber where the thermostat end meets it. Over time the steel rusts and the rubber flakes off, leaving nothing but a rusty metal ring. if you had a silver ring (sounds like stainless steel) then that probably wan't a stock part.