I seem to remember these being mentioned in an older thread on the topic, and if I remember correctly, the consensus was that they were noise dampers in the fluid flow.

This is definitely not authoritative on my part, as it's just a vague memory of seeing them mentioned before, and I suspect that it was partially a guess on the part of others in that thread, though there may have been someone complaining of the system being noisy after replacing the hose and leaving the pieces out.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...