What in H**L is a 034121122 Molded Piece?

[UrS4boy]

I have been trying to help a forum member off-line with a question about a strange black plastic ring he found that was crumbling when changing the thermostat on his ADU. I couldn't figure out what it was and suggested that he just remove it and all the associated debris and then carry on and install the new thermostat. (I gave up)

He carried on and found it. It is a 034121122 "Molded Piece". It is on the ADU thermostat parts list but not the diagram. It is not on the AAN or ABY parts list just the ADU's list. Audi tradition sells them. What I want to know is what is this thing and why was it used on the ADU?

Anybody with ideas?



The AAN (and ABY) diagram. No 034121122 listed but exactly the same thermostat PN:

[Error404]

Never seen any factory info about this, but I believe it is a seal for the back of the thermostat to the block.
Porsche used something similar on the 944 p/n is 95110615500 and may even be the same part.

[mcandmar]

I believe its a restrictor that fits between the thermostat cavity and water pump. Only fitted to RS2's as far as i know.

[rxl]

I believe its a restrictor that fits between the thermostat cavity and water pump. Only fitted to RS2's as far as i know.

[huksa]

It was I who asked UrS4boy for help. And again, he was very willing to help as always.

I was totally lost when I realized there seemed nothing on the parts diagram, but now things are looking better now.

The question is, why only on ADU? Aren't the other engines basically same in their architecture?

[mcandmar]

There were a number of subtle changes to the water cooling pipework in the RS2. The most obvious difference is the smaller water pump pulley which necessitated the use of a different timing belt. But the rest of the differences i believe were around the routing of the after run pump and reservoir tank, but i am unsure of the specific details.

[Error404]

The main one being the pipe from the bottom of the reservoir tee's in just behind the heater matrix return pipe on the side of the block instead of the bottom of the rad.